# SCIP

Solving Constraint Integer Programs

cons_sos1.c
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1 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2 /* */
3 /* This file is part of the program and library */
4 /* SCIP --- Solving Constraint Integer Programs */
5 /* */
7 /* fuer Informationstechnik Berlin */
8 /* */
10 /* */
12 /* along with SCIP; see the file COPYING. If not visit scipopt.org. */
13 /* */
14 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
15
16 /**@file cons_sos1.c
17  * @ingroup DEFPLUGINS_CONS
18  * @brief constraint handler for SOS type 1 constraints
19  * @author Tobias Fischer
20  * @author Marc Pfetsch
21  *
22  * A specially ordered set of type 1 (SOS1) is a sequence of variables such that at most one
23  * variable is nonzero. The special case of two variables arises, for instance, from equilibrium or
24  * complementary conditions like \f$x \cdot y = 0\f$. Note that it is in principle allowed that a
25  * variables appears twice, but it then can be fixed to 0.
26  *
27  * This implementation of this constraint handler is based on classical ideas, see e.g.@n
28  * "Special Facilities in General Mathematical Programming System for
29  * Non-Convex Problems Using Ordered Sets of Variables"@n
30  * E. Beale and J. Tomlin, Proc. 5th IFORS Conference, 447-454 (1970)
31  *
32  *
33  * The order of the variables is determined as follows:
34  *
35  * - If the constraint is created with SCIPcreateConsSOS1() and weights are given, the weights
36  * determine the order (decreasing weights). Additional variables can be added with
38  *
39  * - If an empty constraint is created and then variables are added with SCIPaddVarSOS1(), weights
40  * are needed and stored.
41  *
42  * - All other calls ignore the weights, i.e., if a nonempty constraint is created or variables are
44  *
45  * The validity of the SOS1 constraints can be enforced by different branching rules:
46  *
47  * - If classical SOS branching is used, branching is performed on only one SOS1 constraint.
48  * Depending on the parameters, there are two ways to choose this branching constraint. Either
49  * the constraint with the most number of nonzeros or the one with the largest nonzero-variable
50  * weight. The later version allows the user to specify an order for the branching importance of
51  * the constraints. Constraint branching can also be turned off.
52  *
53  * - Another way is to branch on the neighborhood of a single variable @p i, i.e., in one branch
54  * \f$x_i\f$ is fixed to zero and in the other its neighbors from the conflict graph.
55  *
56  * - If bipartite branching is used, then we branch using complete bipartite subgraphs of the
57  * conflict graph, i.e., in one branch fix the variables from the first bipartite partition and
58  * the variables from the second bipartite partition in the other.
59  *
60  * - In addition to variable domain fixings, it is sometimes also possible to add new SOS1
61  * constraints to the branching nodes. This results in a nonstatic conflict graph, which may
62  * change dynamically with every branching node.
63  *
64  *
65  * @todo Possibly allow to generate local cuts via strengthened local cuts (would need to modified coefficients of rows).
66  *
67  * @todo Check whether we can avoid turning off multi-aggregation (it is sometimes possible to fix a multi-aggregated
68  * variable to 0 by fixing the aggregating variables to 0).
69  */
70
71 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
72
73 #include "blockmemshell/memory.h"
74 #include "scip/cons_linear.h"
75 #include "scip/cons_setppc.h"
76 #include "scip/cons_sos1.h"
77 #include "scip/pub_cons.h"
78 #include "scip/pub_event.h"
79 #include "scip/pub_heur.h"
80 #include "scip/pub_lp.h"
81 #include "scip/pub_message.h"
82 #include "scip/pub_misc.h"
83 #include "scip/pub_misc_sort.h"
84 #include "scip/pub_tree.h"
85 #include "scip/pub_var.h"
86 #include "scip/scip_branch.h"
87 #include "scip/scip_conflict.h"
88 #include "scip/scip_cons.h"
89 #include "scip/scip_copy.h"
90 #include "scip/scip_cut.h"
92 #include "scip/scip_event.h"
93 #include "scip/scip_general.h"
94 #include "scip/scip_lp.h"
95 #include "scip/scip_mem.h"
96 #include "scip/scip_message.h"
97 #include "scip/scip_numerics.h"
98 #include "scip/scip_param.h"
99 #include "scip/scip_prob.h"
100 #include "scip/scip_probing.h"
101 #include "scip/scip_sol.h"
102 #include "scip/scip_solvingstats.h"
103 #include "scip/scip_tree.h"
104 #include "scip/scip_var.h"
105 #include "tclique/tclique.h"
106 #include <ctype.h>
107 #include <stdlib.h>
108 #include <string.h>
109
110
111 /* constraint handler properties */
112 #define CONSHDLR_NAME "SOS1"
113 #define CONSHDLR_DESC "SOS1 constraint handler"
114 #define CONSHDLR_SEPAPRIORITY 1000 /**< priority of the constraint handler for separation */
115 #define CONSHDLR_ENFOPRIORITY 100 /**< priority of the constraint handler for constraint enforcing */
116 #define CONSHDLR_CHECKPRIORITY -10 /**< priority of the constraint handler for checking feasibility */
117 #define CONSHDLR_SEPAFREQ 10 /**< frequency for separating cuts; zero means to separate only in the root node */
118 #define CONSHDLR_PROPFREQ 1 /**< frequency for propagating domains; zero means only preprocessing propagation */
119 #define CONSHDLR_EAGERFREQ 100 /**< frequency for using all instead of only the useful constraints in separation,
120  * propagation and enforcement, -1 for no eager evaluations, 0 for first only */
121 #define CONSHDLR_MAXPREROUNDS -1 /**< maximal number of presolving rounds the constraint handler participates in (-1: no limit) */
122 #define CONSHDLR_DELAYSEPA FALSE /**< should separation method be delayed, if other separators found cuts? */
123 #define CONSHDLR_DELAYPROP FALSE /**< should propagation method be delayed, if other propagators found reductions? */
124 #define CONSHDLR_NEEDSCONS TRUE /**< should the constraint handler be skipped, if no constraints are available? */
125 #define CONSHDLR_PROP_TIMING SCIP_PROPTIMING_BEFORELP
126 #define CONSHDLR_PRESOLTIMING SCIP_PRESOLTIMING_MEDIUM
129 #define DEFAULT_MAXSOSADJACENCY 10000 /**< do not create an adjacency matrix if number of SOS1 variables is larger than predefined value
130  * (-1: no limit) */
131
132 /* presolving */
133 #define DEFAULT_MAXEXTENSIONS 1 /**< maximal number of extensions that will be computed for each SOS1 constraint */
134 #define DEFAULT_MAXTIGHTENBDS 5 /**< maximal number of bound tightening rounds per presolving round (-1: no limit) */
135 #define DEFAULT_PERFIMPLANALYSIS FALSE /**< if TRUE then perform implication graph analysis (might add additional SOS1 constraints) */
136 #define DEFAULT_DEPTHIMPLANALYSIS -1 /**< number of recursive calls of implication graph analysis (-1: no limit) */
138 /* propagation */
139 #define DEFAULT_CONFLICTPROP TRUE /**< whether to use conflict graph propagation */
140 #define DEFAULT_IMPLPROP TRUE /**< whether to use implication graph propagation */
141 #define DEFAULT_SOSCONSPROP FALSE /**< whether to use SOS1 constraint propagation */
143 /* branching rules */
144 #define DEFAULT_BRANCHSTRATEGIES "nbs" /**< possible branching strategies (see parameter DEFAULT_BRANCHINGRULE) */
145 #define DEFAULT_BRANCHINGRULE 'n' /**< which branching rule should be applied ? ('n': neighborhood, 'b': bipartite, 's': SOS1/clique)
146  * (note: in some cases an automatic switching to SOS1 branching is possible) */
147 #define DEFAULT_AUTOSOS1BRANCH TRUE /**< if TRUE then automatically switch to SOS1 branching if the SOS1 constraints do not overlap */
148 #define DEFAULT_FIXNONZERO FALSE /**< if neighborhood branching is used, then fix the branching variable (if positive in sign) to the value of the
149  * feasibility tolerance */
150 #define DEFAULT_ADDCOMPS FALSE /**< if TRUE then add complementarity constraints to the branching nodes (can be used in combination with
151  * neighborhood or bipartite branching) */
152 #define DEFAULT_MAXADDCOMPS -1 /**< maximal number of complementarity constraints added per branching node (-1: no limit) */
153 #define DEFAULT_ADDCOMPSDEPTH 30 /**< only add complementarity constraints to branching nodes for predefined depth (-1: no limit) */
154 #define DEFAULT_ADDCOMPSFEAS -0.6 /**< minimal feasibility value for complementarity constraints in order to be added to the branching node */
155 #define DEFAULT_ADDBDSFEAS 1.0 /**< minimal feasibility value for bound inequalities in order to be added to the branching node */
156 #define DEFAULT_ADDEXTENDEDBDS TRUE /**< should added complementarity constraints be extended to SOS1 constraints to get tighter bound inequalities */
158 /* selection rules */
159 #define DEFAULT_NSTRONGROUNDS 0 /**< maximal number of strong branching rounds to perform for each node (-1: auto)
160  * (only available for neighborhood and bipartite branching) */
161 #define DEFAULT_NSTRONGITER 10000 /**< maximal number LP iterations to perform for each strong branching round (-2: auto, -1: no limit) */
162
163 /* separation */
164 #define DEFAULT_BOUNDCUTSFROMSOS1 FALSE /**< if TRUE separate bound inequalities from SOS1 constraints */
165 #define DEFAULT_BOUNDCUTSFROMGRAPH TRUE /**< if TRUE separate bound inequalities from the conflict graph */
166 #define DEFAULT_AUTOCUTSFROMSOS1 TRUE /**< if TRUE then automatically switch to separating from SOS1 constraints if the SOS1 constraints do not overlap */
167 #define DEFAULT_BOUNDCUTSFREQ 10 /**< frequency for separating bound cuts; zero means to separate only in the root node */
168 #define DEFAULT_BOUNDCUTSDEPTH 40 /**< node depth of separating bound cuts (-1: no limit) */
169 #define DEFAULT_MAXBOUNDCUTS 50 /**< maximal number of bound cuts separated per branching node */
170 #define DEFAULT_MAXBOUNDCUTSROOT 150 /**< maximal number of bound cuts separated per iteration in the root node */
171 #define DEFAULT_STRTHENBOUNDCUTS TRUE /**< if TRUE then bound cuts are strengthened in case bound variables are available */
172 #define DEFAULT_IMPLCUTSFREQ 0 /**< frequency for separating implied bound cuts; zero means to separate only in the root node */
173 #define DEFAULT_IMPLCUTSDEPTH 40 /**< node depth of separating implied bound cuts (-1: no limit) */
174 #define DEFAULT_MAXIMPLCUTS 50 /**< maximal number of implied bound cuts separated per branching node */
175 #define DEFAULT_MAXIMPLCUTSROOT 150 /**< maximal number of implied bound cuts separated per iteration in the root node */
177 /* event handler properties */
178 #define EVENTHDLR_NAME "SOS1"
179 #define EVENTHDLR_DESC "bound change event handler for SOS1 constraints"
181 #define EVENTHDLR_EVENT_TYPE (SCIP_EVENTTYPE_BOUNDCHANGED | SCIP_EVENTTYPE_GBDCHANGED)
182
183 /* defines */
184 #define DIVINGCUTOFFVALUE 1e6
186
187 /** constraint data for SOS1 constraints */
188 struct SCIP_ConsData
189 {
190  int nvars; /**< number of variables in the constraint */
191  int maxvars; /**< maximal number of variables (= size of storage) */
192  int nfixednonzeros; /**< number of variables fixed to be nonzero */
193  SCIP_Bool local; /**< TRUE if constraint is only valid locally */
194  SCIP_VAR** vars; /**< variables in constraint */
195  SCIP_ROW* rowlb; /**< row corresponding to lower bounds, or NULL if not yet created */
196  SCIP_ROW* rowub; /**< row corresponding to upper bounds, or NULL if not yet created */
197  SCIP_Real* weights; /**< weights determining the order (ascending), or NULL if not used */
198 };
199
200
201 /** node data of a given node in the conflict graph */
202 struct SCIP_NodeData
203 {
204  SCIP_VAR* var; /**< variable belonging to node */
205  SCIP_VAR* lbboundvar; /**< bound variable @p z from constraint \f$x \geq \mu \cdot z\f$ (or NULL if not existent) */
206  SCIP_VAR* ubboundvar; /**< bound variable @p z from constraint \f$x \leq \mu \cdot z\f$ (or NULL if not existent) */
207  SCIP_Real lbboundcoef; /**< value \f$\mu\f$ from constraint \f$x \geq \mu z \f$ (0.0 if not existent) */
208  SCIP_Real ubboundcoef; /**< value \f$\mu\f$ from constraint \f$x \leq \mu z \f$ (0.0 if not existent) */
209  SCIP_Bool lbboundcomp; /**< TRUE if the nodes from the connected component of the conflict graph the given node belongs to
210  * all have the same lower bound variable */
211  SCIP_Bool ubboundcomp; /**< TRUE if the nodes from the connected component of the conflict graph the given node belongs to
212  * all have the same lower bound variable */
213 };
214 typedef struct SCIP_NodeData SCIP_NODEDATA;
215
216
217 /** successor data of a given nodes successor in the implication graph */
218 struct SCIP_SuccData
219 {
220  SCIP_Real lbimpl; /**< lower bound implication */
221  SCIP_Real ubimpl; /**< upper bound implication */
222 };
223 typedef struct SCIP_SuccData SCIP_SUCCDATA;
224
225
226 /** tclique data for bound cut generation */
227 struct TCLIQUE_Data
228 {
229  SCIP* scip; /**< SCIP data structure */
230  SCIP_CONSHDLR* conshdlr; /**< SOS1 constraint handler */
231  SCIP_DIGRAPH* conflictgraph; /**< conflict graph */
232  SCIP_SOL* sol; /**< LP solution to be separated (or NULL) */
233  SCIP_Real scaleval; /**< factor for scaling weights */
234  SCIP_Bool cutoff; /**< whether a cutoff occurred */
235  int ncuts; /**< number of bound cuts found in this iteration */
236  int nboundcuts; /**< number of bound cuts found so far */
237  int maxboundcuts; /**< maximal number of clique cuts separated per separation round (-1: no limit) */
238  SCIP_Bool strthenboundcuts; /**< if TRUE then bound cuts are strengthened in case bound variables are available */
239 };
242 /** SOS1 constraint handler data */
243 struct SCIP_ConshdlrData
244 {
245  /* conflict graph */
246  SCIP_DIGRAPH* conflictgraph; /**< conflict graph */
247  SCIP_DIGRAPH* localconflicts; /**< local conflicts */
248  SCIP_Bool isconflocal; /**< if TRUE then local conflicts are present and conflict graph has to be updated for each node */
249  SCIP_HASHMAP* varhash; /**< hash map from variable to node in the conflict graph */
250  int nsos1vars; /**< number of problem variables that are part of the SOS1 conflict graph */
252  int maxsosadjacency; /**< do not create an adjacency matrix if number of SOS1 variables is larger than predefined
253  * value (-1: no limit) */
254  /* implication graph */
255  SCIP_DIGRAPH* implgraph; /**< implication graph (@p j is successor of @p i if and only if \f$x_i\not = 0 \Rightarrow x_j\not = 0\f$) */
256  int nimplnodes; /**< number of nodes in the implication graph */
257  /* tclique graph */
258  TCLIQUE_GRAPH* tcliquegraph; /**< tclique graph data structure */
259  TCLIQUE_DATA* tcliquedata; /**< tclique data */
260  /* event handler */
261  SCIP_EVENTHDLR* eventhdlr; /**< event handler for bound change events */
262  SCIP_VAR** fixnonzerovars; /**< stack of variables fixed to nonzero marked by event handler */
263  int maxnfixnonzerovars; /**< size of stack fixnonzerovars */
264  int nfixnonzerovars; /**< number of variables fixed to nonzero marked by event handler */
265  /* presolving */
266  int cntextsos1; /**< counts number of extended SOS1 constraints */
267  int maxextensions; /**< maximal number of extensions that will be computed for each SOS1 constraint */
268  int maxtightenbds; /**< maximal number of bound tightening rounds per presolving round (-1: no limit) */
269  SCIP_Bool perfimplanalysis; /**< if TRUE then perform implication graph analysis (might add additional SOS1 constraints) */
270  int depthimplanalysis; /**< number of recursive calls of implication graph analysis (-1: no limit) */
271  /* propagation */
272  SCIP_Bool conflictprop; /**< whether to use conflict graph propagation */
273  SCIP_Bool implprop; /**< whether to use implication graph propagation */
274  SCIP_Bool sosconsprop; /**< whether to use SOS1 constraint propagation */
275  /* branching */
276  char branchingrule; /**< which branching rule should be applied ? ('n': neighborhood, 'b': bipartite, 's': SOS1/clique)
277  * (note: in some cases an automatic switching to SOS1 branching is possible) */
278  SCIP_Bool autosos1branch; /**< if TRUE then automatically switch to SOS1 branching if the SOS1 constraints do not overlap */
279  SCIP_Bool fixnonzero; /**< if neighborhood branching is used, then fix the branching variable (if positive in sign) to the value of the
280  * feasibility tolerance */
281  SCIP_Bool addcomps; /**< if TRUE then add complementarity constraints to the branching nodes additionally to domain fixings
282  * (can be used in combination with neighborhood or bipartite branching) */
283  int maxaddcomps; /**< maximal number of complementarity cons. and cor. bound ineq. added per branching node (-1: no limit) */
284  int addcompsdepth; /**< only add complementarity constraints to branching nodes for predefined depth (-1: no limit) */
285  SCIP_Real addcompsfeas; /**< minimal feasibility value for complementarity constraints in order to be added to the branching node */
286  SCIP_Real addbdsfeas; /**< minimal feasibility value for bound inequalities in order to be added to the branching node */
287  SCIP_Bool addextendedbds; /**< should added complementarity constraints be extended to SOS1 constraints to get tighter bound inequalities */
288  SCIP_Bool branchsos; /**< Branch on SOS condition in enforcing? This value can only be set to false if all SOS1 variables are binary */
289  SCIP_Bool branchnonzeros; /**< Branch on SOS cons. with most number of nonzeros? */
290  SCIP_Bool branchweight; /**< Branch on SOS cons. with highest nonzero-variable weight for branching - needs branchnonzeros to be false */
291  SCIP_Bool switchsos1branch; /**< whether to switch to SOS1 branching */
292  /* selection rules */
293  int nstrongrounds; /**< maximal number of strong branching rounds to perform for each node (-1: auto)
294  * (only available for neighborhood and bipartite branching) */
295  int nstrongiter; /**< maximal number LP iterations to perform for each strong branching round (-2: auto, -1: no limit) */
296  /* separation */
297  SCIP_Bool boundcutsfromsos1; /**< if TRUE separate bound inequalities from SOS1 constraints */
298  SCIP_Bool boundcutsfromgraph; /**< if TRUE separate bound inequalities from the conflict graph */
299  SCIP_Bool autocutsfromsos1; /**< if TRUE then automatically switch to separating SOS1 constraints if the SOS1 constraints do not overlap */
300  SCIP_Bool switchcutsfromsos1; /**< whether to switch to separate bound inequalities from SOS1 constraints */
301  int boundcutsfreq; /**< frequency for separating bound cuts; zero means to separate only in the root node */
302  int boundcutsdepth; /**< node depth of separating bound cuts (-1: no limit) */
303  int maxboundcuts; /**< maximal number of bound cuts separated per branching node */
304  int maxboundcutsroot; /**< maximal number of bound cuts separated per iteration in the root node */
305  int nboundcuts; /**< number of bound cuts found so far */
306  SCIP_Bool strthenboundcuts; /**< if TRUE then bound cuts are strengthened in case bound variables are available */
307  int implcutsfreq; /**< frequency for separating implied bound cuts; zero means to separate only in the root node */
308  int implcutsdepth; /**< node depth of separating implied bound cuts (-1: no limit) */
309  int maximplcuts; /**< maximal number of implied bound cuts separated per branching node */
310  int maximplcutsroot; /**< maximal number of implied bound cuts separated per iteration in the root node */
311 };
312
313
314
315 /*
316  * local methods
317  */
318
319 /** returns whether two vertices are adjacent in the conflict graph */
320 static
322  SCIP_Bool** adjacencymatrix, /**< adjacency matrix of conflict graph (lower half) (or NULL if an adjacencymatrix is not at hand) */
323  SCIP_DIGRAPH* conflictgraph, /**< conflict graph (or NULL if an adjacencymatrix is at hand) */
324  int vertex1, /**< first vertex */
325  int vertex2 /**< second vertex */
326  )
327 {
328  assert( adjacencymatrix != NULL || conflictgraph != NULL );
329
330  /* we do not allow self-loops */
331  if ( vertex1 == vertex2 )
332  return FALSE;
333
334  /* for debugging */
335  if ( adjacencymatrix == NULL )
336  {
337  int succvertex;
338  int* succ;
339  int nsucc1;
340  int nsucc2;
341  int j;
342
343  nsucc1 = SCIPdigraphGetNSuccessors(conflictgraph, vertex1);
344  nsucc2 = SCIPdigraphGetNSuccessors(conflictgraph, vertex2);
345
346  if ( nsucc1 < 1 || nsucc2 < 1 )
347  return FALSE;
348
349  if ( nsucc1 > nsucc2 )
350  {
351  SCIPswapInts(&vertex1, &vertex2);
352  SCIPswapInts(&nsucc1, &nsucc2);
353  }
354
355  succ = SCIPdigraphGetSuccessors(conflictgraph, vertex1);
356  SCIPsortInt(succ, nsucc1);
357
358  for (j = 0; j < nsucc1; ++j)
359  {
360  succvertex = succ[j];
361  if ( succvertex == vertex2 )
362  return TRUE;
363  else if ( succvertex > vertex2 )
364  return FALSE;
365  }
366  }
367  else
368  {
369  if ( vertex1 < vertex2 )
371  else
373  }
374
375  return FALSE;
376 }
377
378
379 /** checks whether a variable violates an SOS1 constraint w.r.t. sol together with at least one other variable */
380 static
382  SCIP* scip, /**< SCIP data structure */
383  SCIP_DIGRAPH* conflictgraph, /**< conflict graph (or NULL if an adjacencymatrix is at hand) */
384  int node, /**< node of variable in the conflict graph */
385  SCIP_SOL* sol /**< solution, or NULL to use current node's solution */
386  )
387 {
388  SCIP_Real solval;
389  SCIP_VAR* var;
390
391  assert( scip != NULL );
392  assert( conflictgraph != NULL );
393  assert( node >= 0 );
394
395  var = SCIPnodeGetVarSOS1(conflictgraph, node);
396  assert( var != NULL );
397  solval = SCIPgetSolVal(scip, sol, var);
398
399  /* check whether variable is nonzero w.r.t. sol and the bounds have not been fixed to zero by propagation */
400  if ( ! SCIPisFeasZero(scip, solval) && ( ! SCIPisFeasZero(scip, SCIPvarGetLbLocal(var)) || ! SCIPisFeasZero(scip, SCIPvarGetUbLocal(var)) ) )
401  {
402  int* succ;
403  int nsucc;
404  int s;
405
406  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, node);
407  succ = SCIPdigraphGetSuccessors(conflictgraph, node);
408
409  /* check whether a neighbor variable is nonzero w.r.t. sol */
410  for (s = 0; s < nsucc; ++s)
411  {
412  var = SCIPnodeGetVarSOS1(conflictgraph, succ[s]);
413  assert( var != NULL );
414  solval = SCIPgetSolVal(scip, sol, var);
415  if ( ! SCIPisFeasZero(scip, solval) && ( ! SCIPisFeasZero(scip, SCIPvarGetLbLocal(var)) || ! SCIPisFeasZero(scip, SCIPvarGetUbLocal(var)) ) )
416  return TRUE;
417  }
418  }
419
420  return FALSE;
421 }
422
423
424 /** returns solution value of imaginary binary big-M variable of a given node from the conflict graph */
425 static
427  SCIP* scip, /**< SCIP pointer */
428  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
429  SCIP_SOL* sol, /**< primal solution, or NULL for current LP/pseudo solution */
430  int node /**< node of the conflict graph */
431  )
432 {
434  SCIP_VAR* var;
435  SCIP_Real val;
436
437  assert( scip != NULL );
438  assert( conflictgraph != NULL );
439  assert( node >= 0 && node < SCIPdigraphGetNNodes(conflictgraph) );
440
441  var = SCIPnodeGetVarSOS1(conflictgraph, node);
442  val = SCIPgetSolVal(scip, sol, var);
443
444  if ( SCIPisFeasNegative(scip, val) )
445  {
446  bound = SCIPvarGetLbLocal(var);
447  assert( SCIPisFeasNegative(scip, bound) );
448
449  if ( SCIPisInfinity(scip, -val) )
450  return 1.0;
451  else if ( SCIPisInfinity(scip, -bound) )
452  return 0.0;
453  else
454  return (val/bound);
455  }
456  else if ( SCIPisFeasPositive(scip, val) )
457  {
458  bound = SCIPvarGetUbLocal(var);
459  assert( SCIPisFeasPositive(scip, bound) );
460  assert( SCIPisFeasPositive(scip, val) );
461
462  if ( SCIPisInfinity(scip, val) )
463  return 1.0;
464  else if ( SCIPisInfinity(scip, bound) )
465  return 0.0;
466  else
467  return (val/bound);
468  }
469  else
470  return 0.0;
471 }
472
473
474 /** gets (variable) lower bound value of current LP relaxation solution for a given node from the conflict graph */
475 static
477  SCIP* scip, /**< SCIP pointer */
478  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
479  SCIP_SOL* sol, /**< primal solution, or NULL for current LP/pseudo solution */
480  int node /**< node of the conflict graph */
481  )
482 {
483  SCIP_NODEDATA* nodedata;
484
485  assert( scip != NULL );
486  assert( conflictgraph != NULL );
487  assert( node >= 0 && node < SCIPdigraphGetNNodes(conflictgraph) );
488
489  /* get node data */
490  nodedata = (SCIP_NODEDATA*)SCIPdigraphGetNodeData(conflictgraph, node);
491  assert( nodedata != NULL );
492
493  /* if variable is not involved in a variable upper bound constraint */
494  if ( nodedata->lbboundvar == NULL || ! nodedata->lbboundcomp )
495  return SCIPvarGetLbLocal(nodedata->var);
496
497  return nodedata->lbboundcoef * SCIPgetSolVal(scip, sol, nodedata->lbboundvar);
498 }
499
500
501 /** gets (variable) upper bound value of current LP relaxation solution for a given node from the conflict graph */
502 static
504  SCIP* scip, /**< SCIP pointer */
505  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
506  SCIP_SOL* sol, /**< primal solution, or NULL for current LP/pseudo solution */
507  int node /**< node of the conflict graph */
508  )
509 {
510  SCIP_NODEDATA* nodedata;
511
512  assert( scip != NULL );
513  assert( conflictgraph != NULL );
514  assert( node >= 0 && node < SCIPdigraphGetNNodes(conflictgraph) );
515
516  /* get node data */
517  nodedata = (SCIP_NODEDATA*)SCIPdigraphGetNodeData(conflictgraph, node);
518  assert( nodedata != NULL );
519
520  /* if variable is not involved in a variable upper bound constraint */
521  if ( nodedata->ubboundvar == NULL || ! nodedata->ubboundcomp )
522  return SCIPvarGetUbLocal(nodedata->var);
523
524  return nodedata->ubboundcoef * SCIPgetSolVal(scip, sol, nodedata->ubboundvar);
525 }
526
527
528 /** returns whether variable is part of the SOS1 conflict graph */
529 static
531  SCIP_CONSHDLRDATA* conshdlrdata, /**< SOS1 constraint handler */
532  SCIP_VAR* var /**< variable */
533  )
534 {
535  assert( conshdlrdata != NULL );
536  assert( var != NULL );
537
538  if ( conshdlrdata->varhash == NULL || ! SCIPhashmapExists(conshdlrdata->varhash, var) )
539  return FALSE;
540
541  return TRUE;
542 }
543
544
545 /** returns SOS1 index of variable or -1 if variable is not part of the SOS1 conflict graph */
546 static
547 int varGetNodeSOS1(
548  SCIP_CONSHDLRDATA* conshdlrdata, /**< SOS1 constraint handler */
549  SCIP_VAR* var /**< variable */
550  )
551 {
552  assert( conshdlrdata != NULL );
553  assert( var != NULL );
554  assert( conshdlrdata->varhash != NULL );
555
556  if ( ! SCIPhashmapExists(conshdlrdata->varhash, var) )
557  return -1;
558
559  return SCIPhashmapGetImageInt(conshdlrdata->varhash, var);
560 }
561
562
563 /** fix variable in given node to 0 or add constraint if variable is multi-aggregated
564  *
565  * @todo Try to handle multi-aggregated variables as in fixVariableZero() below.
566  */
567 static
569  SCIP* scip, /**< SCIP pointer */
570  SCIP_VAR* var, /**< variable to be fixed to 0*/
571  SCIP_NODE* node, /**< node */
572  SCIP_Bool* infeasible /**< if fixing is infeasible */
573  )
574 {
575  /* if variable cannot be nonzero */
576  *infeasible = FALSE;
578  {
579  *infeasible = TRUE;
580  return SCIP_OKAY;
581  }
582
583  /* if variable is multi-aggregated */
585  {
586  SCIP_CONS* cons;
587  SCIP_Real val;
588
589  val = 1.0;
590
591  if ( ! SCIPisFeasZero(scip, SCIPvarGetLbLocal(var)) || ! SCIPisFeasZero(scip, SCIPvarGetUbLocal(var)) )
592  {
593  SCIPdebugMsg(scip, "creating constraint to force multi-aggregated variable <%s> to 0.\n", SCIPvarGetName(var));
594  /* we have to insert a local constraint var = 0 */
595  SCIP_CALL( SCIPcreateConsLinear(scip, &cons, "branch", 1, &var, &val, 0.0, 0.0, TRUE, TRUE, TRUE, TRUE, TRUE,
596  TRUE, FALSE, FALSE, FALSE, FALSE) );
597  SCIP_CALL( SCIPaddConsNode(scip, node, cons, NULL) );
598  SCIP_CALL( SCIPreleaseCons(scip, &cons) );
599  }
600  }
601  else
602  {
603  if ( ! SCIPisFeasZero(scip, SCIPvarGetLbLocal(var)) )
604  SCIP_CALL( SCIPchgVarLbNode(scip, node, var, 0.0) );
605  if ( ! SCIPisFeasZero(scip, SCIPvarGetUbLocal(var)) )
606  SCIP_CALL( SCIPchgVarUbNode(scip, node, var, 0.0) );
607  }
608
609  return SCIP_OKAY;
610 }
611
612
613 /** try to fix variable to 0
614  *
615  * Try to treat fixing by special consideration of multiaggregated variables. For a multi-aggregation
616  * \f[
617  * x = \sum_{i=1}^n \alpha_i x_i + c,
618  * \f]
619  * we can express the fixing \f$x = 0\f$ by fixing all \f$x_i\f$ to 0 if \f$c = 0\f$ and the lower bounds of \f$x_i\f$
620  * are nonnegative if \f$\alpha_i > 0\f$ or the upper bounds are nonpositive if \f$\alpha_i < 0\f$.
621  */
622 static
624  SCIP* scip, /**< SCIP pointer */
625  SCIP_VAR* var, /**< variable to be fixed to 0*/
626  SCIP_Bool* infeasible, /**< if fixing is infeasible */
627  SCIP_Bool* tightened /**< if fixing was performed */
628  )
629 {
630  assert( scip != NULL );
631  assert( var != NULL );
632  assert( infeasible != NULL );
633  assert( tightened != NULL );
634
635  *infeasible = FALSE;
636  *tightened = FALSE;
637
639  {
640  SCIP_Real aggrconst;
641
642  /* if constant is 0 */
643  aggrconst = SCIPvarGetMultaggrConstant(var);
644  if ( SCIPisZero(scip, aggrconst) )
645  {
646  SCIP_VAR** aggrvars;
647  SCIP_Real* aggrvals;
648  SCIP_Bool allnonnegative = TRUE;
649  int naggrvars;
650  int i;
651
653
654  /* check whether all variables are "nonnegative" */
655  naggrvars = SCIPvarGetMultaggrNVars(var);
656  aggrvars = SCIPvarGetMultaggrVars(var);
657  aggrvals = SCIPvarGetMultaggrScalars(var);
658  for (i = 0; i < naggrvars; ++i)
659  {
660  if ( (SCIPisPositive(scip, aggrvals[i]) && SCIPisNegative(scip, SCIPvarGetLbLocal(aggrvars[i]))) ||
661  (SCIPisNegative(scip, aggrvals[i]) && SCIPisPositive(scip, SCIPvarGetUbLocal(aggrvars[i]))) )
662  {
663  allnonnegative = FALSE;
664  break;
665  }
666  }
667
668  if ( allnonnegative )
669  {
670  /* all variables are nonnegative -> fix variables */
671  for (i = 0; i < naggrvars; ++i)
672  {
673  SCIP_Bool fixed;
674  SCIP_CALL( SCIPfixVar(scip, aggrvars[i], 0.0, infeasible, &fixed) );
675  if ( *infeasible )
676  return SCIP_OKAY;
677  *tightened = *tightened || fixed;
678  }
679  }
680  }
681  }
682  else
683  {
684  SCIP_CALL( SCIPfixVar(scip, var, 0.0, infeasible, tightened) );
685  }
686
687  return SCIP_OKAY;
688 }
689
690
691 /** fix variable in local node to 0, and return whether the operation was feasible
692  *
693  * @note We do not add a linear constraint if the variable is multi-aggregated as in
694  * fixVariableZeroNode(), since this would be too time consuming.
695  */
696 static
698  SCIP* scip, /**< SCIP pointer */
699  SCIP_VAR* var, /**< variable to be fixed to 0*/
700  SCIP_CONS* cons, /**< constraint */
701  int inferinfo, /**< info for reverse prop. */
702  SCIP_Bool* infeasible, /**< if fixing is infeasible */
703  SCIP_Bool* tightened, /**< if fixing was performed */
704  SCIP_Bool* success /**< whether fixing was successful, i.e., variable is not multi-aggregated */
705  )
706 {
707  *infeasible = FALSE;
708  *tightened = FALSE;
709  *success = FALSE;
710
711  /* if variable cannot be nonzero */
713  {
714  *infeasible = TRUE;
715  return SCIP_OKAY;
716  }
717
718  /* directly fix variable if it is not multi-aggregated */
720  {
721  SCIP_Bool tighten;
722
723  /* fix lower bound */
724  SCIP_CALL( SCIPinferVarLbCons(scip, var, 0.0, cons, inferinfo, FALSE, infeasible, &tighten) );
725  *tightened = *tightened || tighten;
726
727  /* fix upper bound */
728  SCIP_CALL( SCIPinferVarUbCons(scip, var, 0.0, cons, inferinfo, FALSE, infeasible, &tighten) );
729  *tightened = *tightened || tighten;
730
731  *success = TRUE;
732  }
733
734  return SCIP_OKAY;
735 }
736
737
738 /** add lock on variable */
739 static
741  SCIP* scip, /**< SCIP data structure */
742  SCIP_CONS* cons, /**< constraint */
743  SCIP_VAR* var /**< variable */
744  )
745 {
746  assert( scip != NULL );
747  assert( cons != NULL );
748  assert( var != NULL );
749
750  /* rounding down == bad if lb < 0, rounding up == bad if ub > 0 */
751  SCIP_CALL( SCIPlockVarCons(scip, var, cons, SCIPisFeasNegative(scip, SCIPvarGetLbGlobal(var)),
752  SCIPisFeasPositive(scip, SCIPvarGetUbGlobal(var))) );
753
754  return SCIP_OKAY;
755 }
756
757
758 /** remove lock on variable */
759 static
761  SCIP* scip, /**< SCIP data structure */
762  SCIP_CONS* cons, /**< constraint */
763  SCIP_VAR* var /**< variable */
764  )
765 {
766  assert( scip != NULL );
767  assert( cons != NULL );
768  assert( var != NULL );
769
770  /* rounding down == bad if lb < 0, rounding up == bad if ub > 0 */
772  SCIPisFeasPositive(scip, SCIPvarGetUbGlobal(var))) );
773
774  return SCIP_OKAY;
775 }
776
777
778 /** ensures that the vars and weights array can store at least num entries */
779 static
781  SCIP* scip, /**< SCIP data structure */
782  SCIP_CONSDATA* consdata, /**< constraint data */
783  int num, /**< minimum number of entries to store */
784  SCIP_Bool reserveWeights /**< whether the weights array is handled */
785  )
786 {
787  assert( consdata != NULL );
788  assert( consdata->nvars <= consdata->maxvars );
789
790  if ( num > consdata->maxvars )
791  {
792  int newsize;
793
794  newsize = SCIPcalcMemGrowSize(scip, num);
795  SCIP_CALL( SCIPreallocBlockMemoryArray(scip, &consdata->vars, consdata->maxvars, newsize) );
796  if ( reserveWeights )
797  SCIP_CALL( SCIPreallocBlockMemoryArray(scip, &consdata->weights, consdata->maxvars, newsize) );
798  consdata->maxvars = newsize;
799  }
800  assert( num <= consdata->maxvars );
801
802  return SCIP_OKAY;
803 }
804
805
806 /** handle new variable */
807 static
809  SCIP* scip, /**< SCIP data structure */
810  SCIP_CONS* cons, /**< constraint */
811  SCIP_CONSDATA* consdata, /**< constraint data */
812  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
813  SCIP_VAR* var, /**< variable */
814  SCIP_Bool transformed /**< whether original variable was transformed */
815  )
816 {
817  SCIP_DIGRAPH* conflictgraph;
818  int node;
819
820  assert( scip != NULL );
821  assert( cons != NULL );
822  assert( consdata != NULL );
823  assert( conshdlrdata != NULL );
824  assert( var != NULL );
825
826  /* if we are in transformed problem, catch the variable's events */
827  if ( transformed )
828  {
829  assert( conshdlrdata->eventhdlr != NULL );
830
831  /* catch bound change events of variable */
832  SCIP_CALL( SCIPcatchVarEvent(scip, var, EVENTHDLR_EVENT_TYPE, conshdlrdata->eventhdlr,
833  (SCIP_EVENTDATA*)cons, NULL) ); /*lint !e740*/
834
835  /* if the variable if fixed to nonzero */
836  assert( consdata->nfixednonzeros >= 0 );
838  ++consdata->nfixednonzeros;
839  }
840
841  /* install the rounding locks for the new variable */
842  SCIP_CALL( lockVariableSOS1(scip, cons, var) );
843
844  /* branching on multiaggregated variables does not seem to work well, so avoid it */
845  SCIP_CALL( SCIPmarkDoNotMultaggrVar(scip, var) );
846
847  /* add the new coefficient to the upper bound LP row, if necessary */
848  if ( consdata->rowub != NULL && ! SCIPisInfinity(scip, SCIPvarGetUbGlobal(var)) && ! SCIPisZero(scip, SCIPvarGetUbGlobal(var)) )
849  {
850  SCIP_CALL( SCIPaddVarToRow(scip, consdata->rowub, var, 1.0/SCIPvarGetUbGlobal(var)) );
851  }
852
853  /* add the new coefficient to the lower bound LP row, if necessary */
854  if ( consdata->rowlb != NULL && ! SCIPisInfinity(scip, SCIPvarGetLbGlobal(var)) && ! SCIPisZero(scip, SCIPvarGetLbGlobal(var)) )
855  {
856  SCIP_CALL( SCIPaddVarToRow(scip, consdata->rowlb, var, 1.0/SCIPvarGetLbGlobal(var)) );
857  }
858
859  /* return if the conflict graph has not been created yet */
860  conflictgraph = conshdlrdata->conflictgraph;
861  if ( conflictgraph == NULL )
862  return SCIP_OKAY;
863
864  /* get node of variable in the conflict graph (or -1) */
865  node = varGetNodeSOS1(conshdlrdata, var);
866  assert( node < conshdlrdata->nsos1vars );
867
868  /* if the variable is not already a node of the conflict graph */
869  if ( node < 0 )
870  {
871  /* variable does not appear in the conflict graph: switch to SOS1 branching rule, which does not make use of a conflict graph
872  * @todo: maybe recompute the conflict graph, implication graph and varhash instead */
873  SCIPdebugMsg(scip, "Switched to SOS1 branching rule, since conflict graph could be infeasible.\n");
874  conshdlrdata->switchsos1branch = TRUE;
875  return SCIP_OKAY;
876  }
877
878  /* if the constraint is local, then there is no need to act, since local constraints are handled by the local conflict graph in the
879  * function enforceConflictgraph() */
880  if ( ! consdata->local )
881  {
882  SCIP_VAR** vars;
883  int nvars;
884  int v;
885
886  vars = consdata->vars;
887  nvars = consdata->nvars;
888
889  for (v = 0; v < nvars; ++v)
890  {
891  int nodev;
892
893  if ( var == vars[v] )
894  continue;
895
896  /* get node of variable in the conflict graph (or -1) */
897  nodev = varGetNodeSOS1(conshdlrdata, vars[v]);
898  assert( nodev < conshdlrdata->nsos1vars );
899
900  /* if the variable is already a node of the conflict graph */
901  if ( nodev >= 0 )
902  {
903  int nsucc;
904  int nsuccv;
905
906  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, node);
907  nsuccv = SCIPdigraphGetNSuccessors(conflictgraph, nodev);
908
909  /* add arcs if not existent */
910  SCIP_CALL( SCIPdigraphAddArcSafe(conflictgraph, nodev, node, NULL) );
911  SCIP_CALL( SCIPdigraphAddArcSafe(conflictgraph, node, nodev, NULL) );
912
913  /* in case of new arcs: sort successors in ascending order */
914  if ( nsucc < SCIPdigraphGetNSuccessors(conflictgraph, node) )
915  {
916  SCIPdebugMsg(scip, "Added new conflict graph arc from variable %s to variable %s.\n", SCIPvarGetName(var), SCIPvarGetName(vars[v]));
917  SCIPsortInt(SCIPdigraphGetSuccessors(conflictgraph, node), SCIPdigraphGetNSuccessors(conflictgraph, node));
918  }
919
920  if ( nsuccv < SCIPdigraphGetNSuccessors(conflictgraph, nodev) )
921  {
922  SCIPdebugMsg(scip, "Added new conflict graph arc from variable %s to variable %s.\n", SCIPvarGetName(vars[v]), SCIPvarGetName(var));
923  SCIPsortInt(SCIPdigraphGetSuccessors(conflictgraph, nodev), SCIPdigraphGetNSuccessors(conflictgraph, nodev));
924  }
925  }
926  else
927  {
928  /* variable does not appear in the conflict graph: switch to SOS1 branching rule, which does not make use of a conflict graph
929  * @todo: maybe recompute the conflict graph, implication graph and varhash instead */
930  SCIPdebugMsg(scip, "Switched to SOS1 branching rule, since conflict graph could be infeasible.\n");
931  conshdlrdata->switchsos1branch = TRUE;
932  return SCIP_OKAY;
933  }
934  }
935  }
936
937  return SCIP_OKAY;
938 }
939
940
941 /** adds a variable to an SOS1 constraint, at position given by weight - ascending order */
942 static
944  SCIP* scip, /**< SCIP data structure */
945  SCIP_CONS* cons, /**< constraint */
946  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
947  SCIP_VAR* var, /**< variable to add to the constraint */
948  SCIP_Real weight /**< weight to determine position */
949  )
950 {
951  SCIP_CONSDATA* consdata;
952  SCIP_Bool transformed;
953  int pos;
954  int j;
955
956  assert( var != NULL );
957  assert( cons != NULL );
958  assert( conshdlrdata != NULL );
959
960  consdata = SCIPconsGetData(cons);
961  assert( consdata != NULL );
962
963  if ( consdata->weights == NULL && consdata->maxvars > 0 )
964  {
965  SCIPerrorMessage("cannot add variable to SOS1 constraint <%s> that does not contain weights.\n", SCIPconsGetName(cons));
966  return SCIP_INVALIDCALL;
967  }
968
969  /* are we in the transformed problem? */
970  transformed = SCIPconsIsTransformed(cons);
971
972  /* always use transformed variables in transformed constraints */
973  if ( transformed )
974  {
975  SCIP_CALL( SCIPgetTransformedVar(scip, var, &var) );
976  }
977  assert( var != NULL );
978  assert( transformed == SCIPvarIsTransformed(var) );
979
980  SCIP_CALL( consdataEnsurevarsSizeSOS1(scip, consdata, consdata->nvars + 1, TRUE) );
981  assert( consdata->weights != NULL );
982  assert( consdata->maxvars >= consdata->nvars+1 );
983
984  /* find variable position */
985  for (pos = 0; pos < consdata->nvars; ++pos)
986  {
987  if ( consdata->weights[pos] > weight )
988  break;
989  }
990  assert( 0 <= pos && pos <= consdata->nvars );
991
992  /* move other variables, if necessary */
993  for (j = consdata->nvars; j > pos; --j)
994  {
995  consdata->vars[j] = consdata->vars[j-1];
996  consdata->weights[j] = consdata->weights[j-1];
997  }
998
999  /* insert variable */
1000  consdata->vars[pos] = var;
1001  consdata->weights[pos] = weight;
1002  ++consdata->nvars;
1003
1004  /* handle the new variable */
1005  SCIP_CALL( handleNewVariableSOS1(scip, cons, consdata, conshdlrdata, var, transformed) );
1006
1007  return SCIP_OKAY;
1008 }
1009
1010
1011 /** appends a variable to an SOS1 constraint */
1012 static
1014  SCIP* scip, /**< SCIP data structure */
1015  SCIP_CONS* cons, /**< constraint */
1016  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
1017  SCIP_VAR* var /**< variable to add to the constraint */
1018  )
1020  SCIP_CONSDATA* consdata;
1021  SCIP_Bool transformed;
1022
1023  assert( var != NULL );
1024  assert( cons != NULL );
1025  assert( conshdlrdata != NULL );
1026
1027  consdata = SCIPconsGetData(cons);
1028  assert( consdata != NULL );
1029  assert( consdata->nvars >= 0 );
1030
1031  /* are we in the transformed problem? */
1032  transformed = SCIPconsIsTransformed(cons);
1033
1034  /* always use transformed variables in transformed constraints */
1035  if ( transformed )
1036  {
1037  SCIP_CALL( SCIPgetTransformedVar(scip, var, &var) );
1038  }
1039  assert( var != NULL );
1040  assert( transformed == SCIPvarIsTransformed(var) );
1041
1042  if ( consdata->weights != NULL )
1043  {
1044  SCIP_CALL( consdataEnsurevarsSizeSOS1(scip, consdata, consdata->nvars + 1, TRUE) );
1045  }
1046  else
1047  {
1048  SCIP_CALL( consdataEnsurevarsSizeSOS1(scip, consdata, consdata->nvars + 1, FALSE) );
1049  }
1050
1051  /* insert variable */
1052  consdata->vars[consdata->nvars] = var;
1053  if ( consdata->weights != NULL )
1054  {
1055  if ( consdata->nvars > 0 )
1056  consdata->weights[consdata->nvars] = consdata->weights[consdata->nvars-1] + 1.0;
1057  else
1058  consdata->weights[consdata->nvars] = 0.0;
1059  }
1060  ++consdata->nvars;
1061
1062  /* handle the new variable */
1063  SCIP_CALL( handleNewVariableSOS1(scip, cons, consdata, conshdlrdata, var, transformed) );
1064
1065  return SCIP_OKAY;
1066 }
1067
1068
1069 /** deletes a variable of an SOS1 constraint */
1070 static
1072  SCIP* scip, /**< SCIP data structure */
1073  SCIP_CONS* cons, /**< constraint */
1074  SCIP_CONSDATA* consdata, /**< constraint data */
1075  SCIP_EVENTHDLR* eventhdlr, /**< corresponding event handler */
1076  int pos /**< position of variable in array */
1077  )
1078 {
1079  int j;
1080
1081  assert( 0 <= pos && pos < consdata->nvars );
1082
1083  /* remove lock of variable */
1084  SCIP_CALL( unlockVariableSOS1(scip, cons, consdata->vars[pos]) );
1085
1086  /* drop events on variable */
1087  SCIP_CALL( SCIPdropVarEvent(scip, consdata->vars[pos], EVENTHDLR_EVENT_TYPE, eventhdlr, (SCIP_EVENTDATA*)cons, -1) ); /*lint !e740*/
1088
1089  /* delete variable - need to copy since order is important */
1090  for (j = pos; j < consdata->nvars-1; ++j)
1091  {
1092  consdata->vars[j] = consdata->vars[j+1]; /*lint !e679*/
1093  if ( consdata->weights != NULL )
1094  consdata->weights[j] = consdata->weights[j+1]; /*lint !e679*/
1095  }
1096  --consdata->nvars;
1097
1098  return SCIP_OKAY;
1099 }
1100
1101
1102 /* ----------------------------- presolving --------------------------------------*/
1103
1104 /** extends a given clique of the conflict graph
1105  *
1106  * Implementation of the Bron-Kerbosch Algorithm from the paper:
1107  * Algorithm 457: Finding all Cliques of an Undirected Graph, Bron & Kerbosch, Commun. ACM, 1973
1108  */
1109 static
1111  SCIP* scip, /**< SCIP pointer */
1112  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
1113  SCIP_Bool** adjacencymatrix, /**< adjacencymatrix of the conflict graph (only lower half filled) */
1114  SCIP_DIGRAPH* vertexcliquegraph, /**< graph that contains the information which cliques contain a given vertex
1115  * vertices of variables = 0, ..., nsos1vars-1; vertices of cliques = nsos1vars, ..., nsos1vars+ncliques-1*/
1116  int nsos1vars, /**< number of SOS1 variables */
1117  int nconss, /**< number of SOS1 constraints */
1118  SCIP_CONS* cons, /**< constraint to be extended */
1119  SCIP_VAR** vars, /**< variables of extended clique */
1120  SCIP_Real* weights, /**< weights of extended clique */
1121  SCIP_Bool firstcall, /**< whether this is the first call of extension operator */
1122  SCIP_Bool usebacktrack, /**< whether backtracking is needed for the computation */
1123  int** cliques, /**< all cliques found so far */
1124  int* ncliques, /**< number of clique found so far */
1125  int* cliquesizes, /**< number of variables of current clique */
1126  int* newclique, /**< clique we want to extended*/
1127  int* workingset, /**< set of vertices that already served as extension and set of candidates that probably will lead to an extension */
1128  int nworkingset, /**< length of array workingset */
1129  int nexts, /**< number of vertices that already served as extension */
1130  int pos, /**< position of potential candidate */
1131  int* maxextensions, /**< maximal number of extensions */
1133  SCIP_Bool* success /**< pointer to store if at least one new clique was found */
1134  )
1135 {
1136  int* workingsetnew = NULL;
1137  int nextsnew;
1138  int nworkingsetnew;
1139  int mincands;
1140  int btriter = 0; /* backtrack iterator */
1141  int selvertex;
1142  int selpos = -1;
1143  int fixvertex = -1;
1144  int i;
1145  int j;
1146
1147  assert( scip != NULL );
1148  assert( conshdlrdata != NULL );
1149  assert( adjacencymatrix != NULL );
1150  assert( vertexcliquegraph != NULL );
1151  assert( cons != NULL );
1152  assert( cliques != NULL );
1153  assert( cliquesizes != NULL );
1154  assert( newclique != NULL );
1155  assert( workingset != NULL );
1156  assert( maxextensions != NULL );
1157  assert( naddconss != NULL );
1158  assert( success != NULL );
1159
1160  if ( firstcall )
1161  *success = FALSE;
1162
1163  mincands = nworkingset;
1164  if ( mincands < 1 )
1165  return SCIP_OKAY;
1166
1167  /* allocate buffer array */
1168  SCIP_CALL( SCIPallocBufferArray(scip, &workingsetnew, nworkingset) );
1169
1170 #ifdef SCIP_DEBUG
1171  for (i = 0; i < nexts; ++i)
1172  {
1173  for (j = nexts; j < nworkingset; ++j)
1174  {
1175  assert( isConnectedSOS1(adjacencymatrix, NULL, workingset[i], workingset[j]) );
1176  }
1177  }
1178 #endif
1179
1180  /* determine candidate with minimum number of disconnections */
1181  for (i = 0; i < nworkingset; ++i)
1182  {
1183  int vertex;
1184  int cnt = 0;
1185
1186  vertex = workingset[i];
1187
1188  /* count disconnections */
1189  for (j = nexts; j < nworkingset && cnt < mincands; ++j)
1190  {
1191  if ( vertex != workingset[j] && ! isConnectedSOS1(adjacencymatrix, NULL, vertex, workingset[j]) )
1192  {
1193  cnt++;
1194
1195  /* save position of potential candidate */
1196  pos = j;
1197  }
1198  }
1199
1200  /* check whether a new minimum was found */
1201  if ( cnt < mincands )
1202  {
1203  fixvertex = vertex;
1204  mincands = cnt;
1205  if ( i < nexts )
1206  {
1207  assert( pos >= 0 );
1208  selpos = pos;
1209  }
1210  else
1211  {
1212  selpos = i;
1213
1214  /* preincrement */
1215  btriter = 1;
1216  }
1217  }
1218  }
1219
1220  /* If fixed point is initially chosen from candidates then number of disconnections will be preincreased by one. */
1221
1222  /* backtrackcycle */
1223  for (btriter = mincands + btriter; btriter >= 1; --btriter)
1224  {
1225  assert( selpos >= 0);
1226  assert( fixvertex >= 0);
1227
1228  /* interchange */
1229  selvertex = workingset[selpos];
1230  workingset[selpos] = workingset[nexts];
1231  workingset[nexts] = selvertex;
1232
1233  /* create new workingset */
1234  nextsnew = 0;
1235  for (j = 0 ; j < nexts; ++j)
1236  {
1237  if ( isConnectedSOS1(adjacencymatrix, NULL, selvertex, workingset[j]) )
1238  workingsetnew[nextsnew++] = workingset[j];
1239  }
1240  nworkingsetnew = nextsnew;
1241  for (j = nexts + 1; j < nworkingset; ++j)
1242  {
1243  if ( isConnectedSOS1(adjacencymatrix, NULL, selvertex, workingset[j]) )
1244  workingsetnew[nworkingsetnew++] = workingset[j];
1245  }
1246
1247  newclique[cliquesizes[*ncliques]++] = selvertex;
1248
1249  /* if we found a new clique */
1250  if ( nworkingsetnew == 0 )
1251  {
1252  char consname[SCIP_MAXSTRLEN];
1253  SCIP_CONSDATA* consdata;
1254  SCIP_CONS* newcons;
1255  int cliqueind;
1256
1257  cliqueind = nsos1vars + *ncliques; /* index of clique in the vertex-clique graph */
1258
1259  /* save new clique */
1260  assert( cliquesizes[*ncliques] >= 0 && cliquesizes[*ncliques] <= nsos1vars );
1261  assert( *ncliques < MAX(1, conshdlrdata->maxextensions) * nconss );
1262  SCIP_CALL( SCIPallocBlockMemoryArray(scip, &(cliques[*ncliques]), cliquesizes[*ncliques]) );/*lint !e866*/
1263  for (j = 0 ; j < cliquesizes[*ncliques]; ++j)
1264  {
1265  vars[j] = SCIPnodeGetVarSOS1(conshdlrdata->conflictgraph, newclique[j]);
1266  weights[j] = j+1;
1267  cliques[*ncliques][j] = newclique[j];
1268  }
1269
1270  SCIPsortInt(cliques[*ncliques], cliquesizes[*ncliques]);
1271
1272  /* create new constraint */
1273  (void) SCIPsnprintf(consname, SCIP_MAXSTRLEN, "extsos1_%d", conshdlrdata->cntextsos1);
1274
1275  SCIP_CALL( SCIPcreateConsSOS1(scip, &newcons, consname, cliquesizes[*ncliques], vars, weights,
1279  SCIPconsIsDynamic(cons),
1281
1282  consdata = SCIPconsGetData(newcons);
1283
1284  /* add directed edges to the vertex-clique graph */
1285  for (j = 0; j < consdata->nvars; ++j)
1286  {
1287  /* add arc from clique vertex to clique (needed in presolRoundConssSOS1() to delete redundand cliques) */
1288  SCIP_CALL( SCIPdigraphAddArcSafe(vertexcliquegraph, cliques[*ncliques][j], cliqueind, NULL) );
1289  }
1290
1292  SCIP_CALL( SCIPreleaseCons(scip, &newcons) );
1293
1295  ++(conshdlrdata->cntextsos1);
1296  ++(*ncliques);
1297  cliquesizes[*ncliques] = cliquesizes[*ncliques-1]; /* cliquesizes[*ncliques] = size of newclique */
1298
1299  *success = TRUE;
1300
1301  --(*maxextensions);
1302
1303  if ( *maxextensions <= 0 )
1304  {
1305  SCIPfreeBufferArray(scip, &workingsetnew);
1306  return SCIP_OKAY;
1307  }
1308  }
1309  else if ( nextsnew < nworkingsetnew ) /* else if the number of of candidates equals zero */
1310  {
1311  /* if backtracking is used, it is necessary to keep the memory for 'workingsetnew' */
1312  if ( usebacktrack )
1313  {
1314  SCIP_CALL( extensionOperatorSOS1(scip, conshdlrdata, adjacencymatrix, vertexcliquegraph, nsos1vars, nconss, cons, vars, weights, FALSE, usebacktrack,
1315  cliques, ncliques, cliquesizes, newclique, workingsetnew, nworkingsetnew, nextsnew, pos, maxextensions, naddconss, success) );
1316  if ( *maxextensions <= 0 )
1317  {
1318  SCIPfreeBufferArrayNull(scip, &workingsetnew);
1319  return SCIP_OKAY;
1320  }
1321  }
1322  else
1323  {
1324  int w;
1325
1326  assert( nworkingset >= nworkingsetnew );
1327  for (w = 0; w < nworkingsetnew; ++w)
1328  workingset[w] = workingsetnew[w];
1329  nworkingset = nworkingsetnew;
1330
1331  SCIPfreeBufferArrayNull(scip, &workingsetnew);
1332
1333  SCIP_CALL( extensionOperatorSOS1(scip, conshdlrdata, adjacencymatrix, vertexcliquegraph, nsos1vars, nconss, cons, vars, weights, FALSE, usebacktrack,
1334  cliques, ncliques, cliquesizes, newclique, workingset, nworkingset, nextsnew, pos, maxextensions, naddconss, success) );
1335  assert( *maxextensions <= 0 );
1336  return SCIP_OKAY;
1337  }
1338  }
1339  assert( workingsetnew != NULL );
1340  assert( workingset != NULL );
1341
1342  /* remove selvertex from clique */
1343  --cliquesizes[*ncliques];
1344
1345  /* add selvertex to the set of vertices that already served as extension */
1346  ++nexts;
1347
1348  if ( btriter > 1 )
1349  {
1350  /* select a candidate that is not connected to the fixed vertex */
1351  for (j = nexts; j < nworkingset; ++j)
1352  {
1353  assert( fixvertex != workingset[j] );
1354  if ( ! isConnectedSOS1(adjacencymatrix, NULL, fixvertex, workingset[j]) )
1355  {
1356  selpos = j;
1357  break;
1358  }
1359  }
1360  }
1361  }
1362
1363  SCIPfreeBufferArrayNull(scip, &workingsetnew);
1364
1365  return SCIP_OKAY;
1366 }
1367
1368
1369 /** generates conflict graph that is induced by the variables of a linear constraint */
1370 static
1372  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
1373  SCIP_DIGRAPH* conflictgraphlin, /**< conflict graph of linear constraint (nodes: 1, ..., nlinvars) */
1374  SCIP_DIGRAPH* conflictgraphorig, /**< original conflict graph (nodes: 1, ..., nsos1vars) */
1375  SCIP_VAR** linvars, /**< linear variables in linear constraint */
1376  int nlinvars, /**< number of linear variables in linear constraint */
1377  int* posinlinvars /**< posinlinvars[i] = position (index) of SOS1 variable i in linear constraint,
1378  * posinlinvars[i]= -1 if @p i is not a SOS1 variable or not a variable of the linear constraint */
1379  )
1380 {
1381  int indexinsosvars;
1382  int indexinlinvars;
1383  int* succ;
1384  int nsucc;
1385  int v;
1386  int s;
1387
1388  assert( conflictgraphlin != NULL );
1389  assert( conflictgraphorig != NULL );
1390  assert( linvars != NULL );
1391  assert( posinlinvars != NULL );
1392
1393  for (v = 1; v < nlinvars; ++v) /* we start with v = 1, since "indexinlinvars < v" (see below) is never fulfilled for v = 0 */
1394  {
1395  indexinsosvars = varGetNodeSOS1(conshdlrdata, linvars[v]);
1396
1397  /* if linvars[v] is contained in at least one SOS1 constraint */
1398  if ( indexinsosvars >= 0 )
1399  {
1400  succ = SCIPdigraphGetSuccessors(conflictgraphorig, indexinsosvars);
1401  nsucc = SCIPdigraphGetNSuccessors(conflictgraphorig, indexinsosvars);
1402
1403  for (s = 0; s < nsucc; ++s)
1404  {
1405  assert( succ[s] >= 0 );
1406  indexinlinvars = posinlinvars[succ[s]];
1407  assert( indexinlinvars < nlinvars );
1408
1409  if ( indexinlinvars >= 0 && indexinlinvars < v )
1410  {
1411  SCIP_CALL( SCIPdigraphAddArcSafe(conflictgraphlin, v, indexinlinvars, NULL) );
1412  SCIP_CALL( SCIPdigraphAddArcSafe(conflictgraphlin, indexinlinvars, v, NULL) );
1413  }
1414  }
1415  }
1416  }
1417
1418  return SCIP_OKAY;
1419 }
1420
1421
1422 /** determine the common successors of the vertices from the considered clique */
1423 static
1425  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
1426  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
1427  int* clique, /**< current clique */
1428  SCIP_VAR** vars, /**< clique variables */
1429  int nvars, /**< number of clique variables */
1430  int* comsucc, /**< pointer to store common successors of clique vertices (size = nvars) */
1431  int* ncomsucc /**< pointer to store number common successors of clique vertices */
1432  )
1433 {
1434  int nsucc;
1435  int* succ;
1436  int ind;
1437  int k = 0;
1438  int v;
1439  int i;
1440  int j;
1441
1442  assert( conflictgraph != NULL );
1443  assert( clique != NULL );
1444  assert( vars != NULL );
1445  assert( comsucc != NULL );
1446  assert( ncomsucc != NULL );
1447
1448  *ncomsucc = 0;
1449
1450  /* determine the common successors of the vertices from the considered clique */
1451
1452  /* determine successors of variable var[0] that are not in the clique */
1453  assert(vars[0] != NULL );
1454  ind = varGetNodeSOS1(conshdlrdata, vars[0]);
1455
1456  if( ind == -1 )
1457  return SCIP_INVALIDDATA;
1458
1459  assert( ind < SCIPdigraphGetNNodes(conflictgraph) );
1460  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, ind);
1461  succ = SCIPdigraphGetSuccessors(conflictgraph, ind);
1462
1463  for (j = 0; j < nvars; ++j)
1464  {
1465  for (i = k; i < nsucc; ++i)
1466  {
1467  if ( succ[i] > clique[j] )
1468  {
1469  k = i;
1470  break;
1471  }
1472  else if ( succ[i] == clique[j] )
1473  {
1474  k = i + 1;
1475  break;
1476  }
1477  else
1478  comsucc[(*ncomsucc)++] = succ[i];
1479  }
1480  }
1481
1482  /* for all variables except the first one */
1483  for (v = 1; v < nvars; ++v)
1484  {
1485  int ncomsuccsave = 0;
1486  k = 0;
1487
1488  assert(vars[v] != NULL );
1489  ind = varGetNodeSOS1(conshdlrdata, vars[v]);
1490  assert( ind >= 0 && ind < SCIPdigraphGetNNodes(conflictgraph) );
1491
1492  if ( ind >= 0 )
1493  {
1494  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, ind);
1495  succ = SCIPdigraphGetSuccessors(conflictgraph, ind);
1496
1497  /* determine successors that are in comsucc */
1498  for (j = 0; j < *ncomsucc; ++j)
1499  {
1500  for (i = k; i < nsucc; ++i)
1501  {
1502  if ( succ[i] > comsucc[j] )
1503  {
1504  k = i;
1505  break;
1506  }
1507  else if ( succ[i] == comsucc[j] )
1508  {
1509  comsucc[ncomsuccsave++] = succ[i];
1510  k = i + 1;
1511  break;
1512  }
1513  }
1514  }
1515  *ncomsucc = ncomsuccsave;
1516  }
1517  }
1518
1519  return SCIP_OKAY;
1520 }
1521
1522
1523 /** get nodes whose corresponding SOS1 variables are nonzero if an SOS1 variable of a given node is nonzero */
1524 static
1526  SCIP* scip, /**< SCIP pointer */
1527  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
1528  SCIP_VAR** vars, /**< problem and SOS1 variables */
1529  SCIP_DIGRAPH* implgraph, /**< implication graph (@p j is successor of @p i if and only if \f$x_i\not = 0 \Rightarrow x_j\not = 0\f$) */
1530  SCIP_HASHMAP* implhash, /**< hash map from variable to node in implication graph */
1531  SCIP_Bool* implnodes, /**< implnodes[i] = TRUE if the SOS1 variable corresponding to node i in the implication graph is implied to be nonzero */
1532  int node /**< node of the implication graph */
1533  )
1534 {
1535  SCIP_SUCCDATA** succdatas;
1536  int sos1node;
1537  int* succ;
1538  int nsucc;
1539  int s;
1540
1541  assert( scip != NULL );
1542  assert( implgraph != NULL );
1543  assert( implnodes != NULL );
1544  assert( node >= 0 );
1545  assert( vars[node] != NULL );
1546  assert( SCIPhashmapGetImageInt(implhash, vars[node]) == node );
1547
1548  /* get node of variable in the conflict graph (-1 if variable is no SOS1 variable) */
1549  sos1node = varGetNodeSOS1(conshdlrdata, vars[node]);
1550  if ( sos1node < 0 )
1551  return SCIP_OKAY;
1552
1553  succdatas = (SCIP_SUCCDATA**) SCIPdigraphGetSuccessorsData(implgraph, node);
1554  nsucc = SCIPdigraphGetNSuccessors(implgraph, node);
1555  succ = SCIPdigraphGetSuccessors(implgraph, node);
1556
1557  for (s = 0; s < nsucc; ++s)
1558  {
1559  SCIP_SUCCDATA* data;
1560  int succnode;
1561  succnode = succ[s];
1562  data = succdatas[s];
1563  sos1node = varGetNodeSOS1(conshdlrdata, vars[succnode]);
1564
1565  /* if node is SOS1 and the corresponding variable is implied to be nonzero */
1566  assert( succdatas[s] != NULL );
1567  if ( sos1node >= 0 && ! implnodes[sos1node] && ( SCIPisFeasPositive(scip, data->lbimpl) || SCIPisFeasNegative(scip, data->ubimpl) ) )
1568  {
1569  assert( sos1node == succnode );
1570  implnodes[sos1node] = TRUE;
1571  SCIP_CALL( getSOS1Implications(scip, conshdlrdata, vars, implgraph, implhash, implnodes, succnode) );
1572  }
1573  }
1574
1575  return SCIP_OKAY;
1576 }
1577
1578
1579 /** perform one presolving round for a single SOS1 constraint
1580  *
1581  * We perform the following presolving steps.
1582  *
1583  * - If the bounds of some variable force it to be nonzero, we can
1584  * fix all other variables to zero and remove the SOS1 constraints
1585  * that contain it.
1586  * - If a variable is fixed to zero, we can remove the variable.
1587  * - If a variable appears twice, it can be fixed to 0.
1588  * - We substitute appregated variables.
1589  */
1590 static
1592  SCIP* scip, /**< SCIP pointer */
1593  SCIP_CONS* cons, /**< constraint */
1594  SCIP_CONSDATA* consdata, /**< constraint data */
1595  SCIP_EVENTHDLR* eventhdlr, /**< event handler */
1596  SCIP_Bool* substituted, /**< whether a variable was substituted */
1597  SCIP_Bool* cutoff, /**< whether a cutoff happened */
1598  SCIP_Bool* success, /**< whether we performed a successful reduction */
1599  int* ndelconss, /**< number of deleted constraints */
1600  int* nupgdconss, /**< number of upgraded constraints */
1601  int* nfixedvars, /**< number of fixed variables */
1602  int* nremovedvars /**< number of variables removed */
1603  )
1604 {
1605  SCIP_VAR** vars;
1606  SCIP_Bool allvarsbinary;
1607  SCIP_Bool infeasible;
1608  SCIP_Bool fixed;
1609  int nfixednonzeros;
1610  int lastFixedNonzero;
1611  int j;
1612
1613  assert( scip != NULL );
1614  assert( cons != NULL );
1615  assert( consdata != NULL );
1616  assert( eventhdlr != NULL );
1617  assert( cutoff != NULL );
1618  assert( success != NULL );
1619  assert( ndelconss != NULL );
1620  assert( nfixedvars != NULL );
1621  assert( nremovedvars != NULL );
1622
1623  *substituted = FALSE;
1624  *cutoff = FALSE;
1625  *success = FALSE;
1626
1627  SCIPdebugMsg(scip, "Presolving SOS1 constraint <%s>.\n", SCIPconsGetName(cons) );
1628
1629  j = 0;
1630  nfixednonzeros = 0;
1631  lastFixedNonzero = -1;
1632  allvarsbinary = TRUE;
1633  vars = consdata->vars;
1634
1635  /* check for variables fixed to 0 and bounds that fix a variable to be nonzero */
1636  while ( j < consdata->nvars )
1637  {
1638  int l;
1639  SCIP_VAR* var;
1640  SCIP_Real lb;
1641  SCIP_Real ub;
1642  SCIP_Real scalar;
1643  SCIP_Real constant;
1644
1645  scalar = 1.0;
1646  constant = 0.0;
1647
1648  /* check for aggregation: if the constant is zero the variable is zero iff the aggregated
1649  * variable is 0 */
1650  var = vars[j];
1651  SCIP_CALL( SCIPgetProbvarSum(scip, &var, &scalar, &constant) );
1652
1653  /* if constant is zero and we get a different variable, substitute variable */
1654  if ( SCIPisZero(scip, constant) && ! SCIPisZero(scip, scalar) && var != vars[j] )
1655  {
1656  SCIPdebugMsg(scip, "substituted variable <%s> by <%s>.\n", SCIPvarGetName(vars[j]), SCIPvarGetName(var));
1657  SCIP_CALL( SCIPdropVarEvent(scip, consdata->vars[j], EVENTHDLR_EVENT_TYPE, eventhdlr, (SCIP_EVENTDATA*)cons, -1) ); /*lint !e740*/
1658  SCIP_CALL( SCIPcatchVarEvent(scip, var, EVENTHDLR_EVENT_TYPE, eventhdlr, (SCIP_EVENTDATA*)cons, NULL) ); /*lint !e740*/
1659
1660  /* change the rounding locks */
1661  SCIP_CALL( unlockVariableSOS1(scip, cons, consdata->vars[j]) );
1662  SCIP_CALL( lockVariableSOS1(scip, cons, var) );
1663
1664  vars[j] = var;
1665  *substituted = TRUE;
1666  }
1667
1668  /* check whether the variable appears again later */
1669  for (l = j+1; l < consdata->nvars; ++l)
1670  {
1671  /* if variable appeared before, we can fix it to 0 and remove it */
1672  if ( vars[j] == vars[l] )
1673  {
1674  SCIPdebugMsg(scip, "variable <%s> appears twice in constraint, fixing it to 0.\n", SCIPvarGetName(vars[j]));
1675  SCIP_CALL( SCIPfixVar(scip, vars[j], 0.0, &infeasible, &fixed) );
1676
1677  if ( infeasible )
1678  {
1679  *cutoff = TRUE;
1680  return SCIP_OKAY;
1681  }
1682  if ( fixed )
1683  ++(*nfixedvars);
1684  }
1685  }
1686
1687  /* get bounds */
1688  lb = SCIPvarGetLbLocal(vars[j]);
1689  ub = SCIPvarGetUbLocal(vars[j]);
1690
1691  /* if the variable if fixed to nonzero */
1692  if ( SCIPisFeasPositive(scip, lb) || SCIPisFeasNegative(scip, ub) )
1693  {
1694  ++nfixednonzeros;
1695  lastFixedNonzero = j;
1696  }
1697
1698  /* if the variable is fixed to 0 */
1699  if ( SCIPisFeasZero(scip, lb) && SCIPisFeasZero(scip, ub) )
1700  {
1701  SCIPdebugMsg(scip, "deleting variable <%s> fixed to 0.\n", SCIPvarGetName(vars[j]));
1702  SCIP_CALL( deleteVarSOS1(scip, cons, consdata, eventhdlr, j) );
1703  ++(*nremovedvars);
1704  }
1705  else
1706  {
1707  /* check whether all variables are binary */
1708  if ( ! SCIPvarIsBinary(vars[j]) )
1709  allvarsbinary = FALSE;
1710
1711  ++j;
1712  }
1713  }
1714
1715  /* if the number of variables is less than 2 */
1716  if ( consdata->nvars < 2 )
1717  {
1718  SCIPdebugMsg(scip, "Deleting SOS1 constraint <%s> with < 2 variables.\n", SCIPconsGetName(cons));
1719
1720  /* delete constraint */
1721  assert( ! SCIPconsIsModifiable(cons) );
1722  SCIP_CALL( SCIPdelCons(scip, cons) );
1723  ++(*ndelconss);
1724  *success = TRUE;
1725  return SCIP_OKAY;
1726  }
1727
1728  /* if more than one variable are fixed to be nonzero, we are infeasible */
1729  if ( nfixednonzeros > 1 )
1730  {
1731  SCIPdebugMsg(scip, "The problem is infeasible: more than one variable has bounds that keep it from being 0.\n");
1732  assert( lastFixedNonzero >= 0 );
1733  *cutoff = TRUE;
1734  return SCIP_OKAY;
1735  }
1736
1737  /* if there is exactly one fixed nonzero variable */
1738  if ( nfixednonzeros == 1 )
1739  {
1740  assert( lastFixedNonzero >= 0 );
1741
1742  /* fix all other variables to zero */
1743  for (j = 0; j < consdata->nvars; ++j)
1744  {
1745  if ( j != lastFixedNonzero )
1746  {
1747  SCIP_CALL( fixVariableZero(scip, vars[j], &infeasible, &fixed) );
1748  if ( infeasible )
1749  {
1750  *cutoff = TRUE;
1751  return SCIP_OKAY;
1752  }
1753  if ( fixed )
1754  ++(*nfixedvars);
1755  }
1756  }
1757
1758  SCIPdebugMsg(scip, "Deleting redundant SOS1 constraint <%s> with one variable.\n", SCIPconsGetName(cons));
1759
1760  /* delete original constraint */
1761  assert( ! SCIPconsIsModifiable(cons) );
1762  SCIP_CALL( SCIPdelCons(scip, cons) );
1763  ++(*ndelconss);
1764  *success = TRUE;
1765  }
1766  /* note: there is no need to update consdata->nfixednonzeros, since the constraint is deleted as soon nfixednonzeros > 0. */
1767  else
1768  {
1769  /* if all variables are binary create a set packing constraint */
1770  if ( allvarsbinary && SCIPfindConshdlr(scip, "setppc") != NULL )
1771  {
1772  SCIP_CONS* setpackcons;
1773
1774  /* create, add, and release the logicor constraint */
1775  SCIP_CALL( SCIPcreateConsSetpack(scip, &setpackcons, SCIPconsGetName(cons), consdata->nvars, consdata->vars,
1780  SCIP_CALL( SCIPreleaseCons(scip, &setpackcons) );
1781
1782  SCIPdebugMsg(scip, "Upgrading SOS1 constraint <%s> to set packing constraint.\n", SCIPconsGetName(cons));
1783
1784  /* remove the SOS1 constraint globally */
1785  assert( ! SCIPconsIsModifiable(cons) );
1786  SCIP_CALL( SCIPdelCons(scip, cons) );
1787  ++(*nupgdconss);
1788  *success = TRUE;
1789  }
1790  }
1791
1792  return SCIP_OKAY;
1793 }
1794
1795
1796
1797 /** perform one presolving round for all SOS1 constraints
1798  *
1799  * We perform the following presolving steps.
1800  *
1801  * - If the bounds of some variable force it to be nonzero, we can
1802  * fix all other variables to zero and remove the SOS1 constraints
1803  * that contain it.
1804  * - If a variable is fixed to zero, we can remove the variable.
1805  * - If a variable appears twice, it can be fixed to 0.
1806  * - We substitute appregated variables.
1807  * - Remove redundant SOS1 constraints
1808  *
1809  * If the adjacency matrix of the conflict graph is present, then
1810  * we perform the following additional presolving steps
1811  *
1812  * - Search for larger SOS1 constraints in the conflict graph
1813  *
1814  * @todo Use one long array for storing cliques.
1815  */
1816 static
1818  SCIP* scip, /**< SCIP pointer */
1819  SCIP_EVENTHDLR* eventhdlr, /**< event handler */
1820  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
1821  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
1822  SCIP_Bool** adjacencymatrix, /**< adjacency matrix of conflict graph (or NULL) */
1823  SCIP_CONS** conss, /**< SOS1 constraints */
1824  int nconss, /**< number of SOS1 constraints */
1825  int nsos1vars, /**< number of SOS1 variables */
1827  int* ndelconss, /**< number of deleted constraints */
1828  int* nupgdconss, /**< number of upgraded constraints */
1829  int* nfixedvars, /**< number of fixed variables */
1830  int* nremovedvars, /**< number of variables removed */
1831  SCIP_RESULT* result /**< result */
1832  )
1833 {
1834  SCIP_DIGRAPH* vertexcliquegraph;
1835  SCIP_VAR** consvars;
1836  SCIP_Real* consweights;
1837  int** cliques = NULL;
1838  int ncliques = 0;
1839  int* cliquesizes = NULL;
1840  int* newclique = NULL;
1841  int* indconss = NULL;
1842  int* lengthconss = NULL;
1843  int* comsucc = NULL;
1844  int csize;
1845  int iter;
1846  int c;
1847
1848  assert( scip != NULL );
1849  assert( eventhdlr != NULL );
1850  assert( conshdlrdata != NULL );
1851  assert( conflictgraph != NULL );
1852  assert( conss != NULL );
1853  assert( naddconss != NULL );
1854  assert( ndelconss != NULL );
1855  assert( nupgdconss != NULL );
1856  assert( nfixedvars != NULL );
1857  assert( nremovedvars != NULL );
1858  assert( result != NULL );
1859
1860  /* create digraph whose nodes represent variables and cliques in the conflict graph */
1861  csize = MAX(1, conshdlrdata->maxextensions) * nconss;
1862  SCIP_CALL( SCIPcreateDigraph(scip, &vertexcliquegraph, nsos1vars + csize) );
1863
1864  /* allocate buffer arrays */
1865  SCIP_CALL( SCIPallocBufferArray(scip, &consvars, nsos1vars) );
1866  SCIP_CALL( SCIPallocBufferArray(scip, &consweights, nsos1vars) );
1867  SCIP_CALL( SCIPallocBufferArray(scip, &newclique, nsos1vars) );
1868  SCIP_CALL( SCIPallocBufferArray(scip, &indconss, csize) );
1869  SCIP_CALL( SCIPallocBufferArray(scip, &lengthconss, csize) );
1870  SCIP_CALL( SCIPallocBufferArray(scip, &comsucc, MAX(nsos1vars, csize)) );
1871
1872  /* Use block memory for cliques, because sizes might be quite different and allocation interfers with workingset. */
1873  SCIP_CALL( SCIPallocBlockMemoryArray(scip, &cliquesizes, csize) );
1874  SCIP_CALL( SCIPallocBlockMemoryArray(scip, &cliques, csize) );
1875
1876  /* get constraint indices and sort them in descending order of their lengths */
1877  for (c = 0; c < nconss; ++c)
1878  {
1879  SCIP_CONSDATA* consdata;
1880
1881  consdata = SCIPconsGetData(conss[c]);
1882  assert( consdata != NULL );
1883
1884  indconss[c] = c;
1885  lengthconss[c] = consdata->nvars;
1886  }
1887  SCIPsortDownIntInt(lengthconss, indconss, nconss);
1888
1889  /* check each constraint */
1890  for (iter = 0; iter < nconss; ++iter)
1891  {
1892  SCIP_CONSDATA* consdata;
1893  SCIP_CONS* cons;
1894  SCIP_Bool substituted;
1895  SCIP_Bool success;
1896  SCIP_Bool cutoff;
1897  int savennupgdconss;
1898  int savendelconss;
1899
1900  SCIP_VAR** vars;
1901  int nvars;
1902
1903  c = indconss[iter];
1904
1905  assert( conss != NULL );
1906  assert( conss[c] != NULL );
1907  cons = conss[c];
1908  consdata = SCIPconsGetData(cons);
1909
1910  assert( consdata != NULL );
1911  assert( consdata->nvars >= 0 );
1912  assert( consdata->nvars <= consdata->maxvars );
1913  assert( ! SCIPconsIsModifiable(cons) );
1914  assert( ncliques < csize );
1915
1916  savendelconss = *ndelconss;
1917  savennupgdconss = *nupgdconss;
1918
1919  /* perform one presolving round for SOS1 constraint */
1920  SCIP_CALL( presolRoundConsSOS1(scip, cons, consdata, eventhdlr, &substituted, &cutoff, &success, ndelconss, nupgdconss, nfixedvars, nremovedvars) );
1921
1922  if ( cutoff )
1923  {
1924  *result = SCIP_CUTOFF;
1925  break;
1926  }
1927
1928  if ( *ndelconss > savendelconss || *nupgdconss > savennupgdconss || substituted )
1929  {
1930  *result = SCIP_SUCCESS;
1931  continue;
1932  }
1933
1934  if ( success )
1935  *result = SCIP_SUCCESS;
1936
1937  /* get number of variables of constraint */
1938  nvars = consdata->nvars;
1939
1940  /* get variables of constraint */
1941  vars = consdata->vars;
1942
1943  if ( nvars > 1 && conshdlrdata->maxextensions != 0 )
1944  {
1945  SCIP_Bool extended = FALSE;
1946  int cliquesize = 0;
1947  int ncomsucc = 0;
1948  int varprobind;
1949  int j;
1950
1951  /* get clique and size of clique */
1952  for (j = 0; j < nvars; ++j)
1953  {
1954  varprobind = varGetNodeSOS1(conshdlrdata, vars[j]);
1955
1956  if ( varprobind >= 0 )
1957  newclique[cliquesize++] = varprobind;
1958  }
1959
1960  if ( cliquesize > 1 )
1961  {
1962  cliquesizes[ncliques] = cliquesize;
1963
1964  /* sort clique vertices */
1965  SCIPsortInt(newclique, cliquesizes[ncliques]);
1966
1967  /* check if clique is contained in an already known clique */
1968  if ( ncliques > 0 )
1969  {
1970  int* succ;
1971  int nsucc;
1972  int v;
1973
1974  varprobind = newclique[0];
1975  ncomsucc = SCIPdigraphGetNSuccessors(vertexcliquegraph, varprobind);
1976  succ = SCIPdigraphGetSuccessors(vertexcliquegraph, varprobind);
1977
1978  /* get all (already processed) cliques that contain 'varpropind' */
1979  for (j = 0; j < ncomsucc; ++j)
1980  {
1981  /* successors should have been sorted in a former step of the algorithm */
1982  assert( j == 0 || succ[j] > succ[j-1] );
1983  comsucc[j] = succ[j];
1984  }
1985
1986  /* loop through remaining nodes of clique (case v = 0 already processed) */
1987  for (v = 1; v < cliquesize && ncomsucc > 0; ++v)
1988  {
1989  varprobind = newclique[v];
1990
1991  /* get all (already processed) cliques that contain 'varpropind' */
1992  nsucc = SCIPdigraphGetNSuccessors(vertexcliquegraph, varprobind);
1993  succ = SCIPdigraphGetSuccessors(vertexcliquegraph, varprobind);
1994  assert( succ != NULL || nsucc == 0 );
1995
1996  if ( nsucc < 1 )
1997  {
1998  ncomsucc = 0;
1999  break;
2000  }
2001
2002  /* get intersection with comsucc */
2003  SCIPcomputeArraysIntersectionInt(comsucc, ncomsucc, succ, nsucc, comsucc, &ncomsucc);
2004  }
2005  }
2006
2007  /* if constraint is redundand then delete it */
2008  if ( ncomsucc > 0 )
2009  {
2010  assert( ! SCIPconsIsModifiable(cons) );
2011  SCIP_CALL( SCIPdelCons(scip, cons) );
2012  ++(*ndelconss);
2013  *result = SCIP_SUCCESS;
2014  continue;
2015  }
2016
2017  if ( conshdlrdata->maxextensions != 0 && adjacencymatrix != NULL )
2018  {
2019  int maxextensions;
2020  ncomsucc = 0;
2021
2022  /* determine the common successors of the vertices from the considered clique */
2023  SCIP_CALL( cliqueGetCommonSuccessorsSOS1(conshdlrdata, conflictgraph, newclique, vars, nvars, comsucc, &ncomsucc) );
2024
2025  /* find extensions for the clique */
2026  maxextensions = conshdlrdata->maxextensions;
2027  extended = FALSE;
2028  SCIP_CALL( extensionOperatorSOS1(scip, conshdlrdata, adjacencymatrix, vertexcliquegraph, nsos1vars, nconss, cons, consvars, consweights,
2029  TRUE, (maxextensions <= 1) ? FALSE : TRUE, cliques, &ncliques, cliquesizes, newclique, comsucc, ncomsucc, 0, -1, &maxextensions,
2031  }
2032
2033  /* if an extension was found for the current clique then free the old SOS1 constraint */
2034  if ( extended )
2035  {
2036  assert( ! SCIPconsIsModifiable(cons) );
2037  SCIP_CALL( SCIPdelCons(scip, cons) );
2038  ++(*ndelconss);
2039  *result = SCIP_SUCCESS;
2040  }
2041  else /* if we keep the constraint */
2042  {
2043  int cliqueind;
2044
2045  cliqueind = nsos1vars + ncliques; /* index of clique in vertex-clique graph */
2046
2047  /* add directed edges to the vertex-clique graph */
2048  assert( cliquesize >= 0 && cliquesize <= nsos1vars );
2049  assert( ncliques < csize );
2050  SCIP_CALL( SCIPallocBlockMemoryArray(scip, &cliques[ncliques], cliquesize) );/*lint !e866*/
2051  for (j = 0; j < cliquesize; ++j)
2052  {
2053  cliques[ncliques][j] = newclique[j];
2054  SCIP_CALL( SCIPdigraphAddArcSafe(vertexcliquegraph, cliques[ncliques][j], cliqueind, NULL) );
2055  }
2056
2057  /* update number of maximal cliques */
2058  ++ncliques;
2059  }
2060  }
2061  }
2062  }
2063
2064  /* free buffer arrays */
2065  for (c = ncliques-1; c >= 0; --c)
2066  SCIPfreeBlockMemoryArray(scip, &cliques[c], cliquesizes[c]);
2067  SCIPfreeBlockMemoryArrayNull(scip, &cliques, csize);
2068  SCIPfreeBlockMemoryArrayNull(scip, &cliquesizes, csize);
2069
2070  SCIPfreeBufferArrayNull(scip, &comsucc);
2071  SCIPfreeBufferArrayNull(scip, &lengthconss);
2072  SCIPfreeBufferArrayNull(scip, &indconss);
2073  SCIPfreeBufferArrayNull(scip, &newclique);
2074  SCIPfreeBufferArrayNull(scip, &consweights);
2075  SCIPfreeBufferArrayNull(scip, &consvars);
2076  SCIPdigraphFree(&vertexcliquegraph);
2077
2078  return SCIP_OKAY;
2079 }
2080
2081
2082 /** performs implication graph analysis
2083  *
2084  * Tentatively fixes a variable to nonzeero and extracts consequences from it:
2085  * - adds (possibly new) complementarity constraints to the problem if variables are implied to be zero
2086  * - returns that the subproblem is infeasible if the domain of a variable turns out to be empty
2087  */
2088 static
2090  SCIP* scip, /**< SCIP pointer */
2091  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
2092  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
2093  SCIP_VAR** totalvars, /**< problem and SOS1 variables */
2094  SCIP_DIGRAPH* implgraph, /**< implication graph (@p j is successor of @p i if and only if \f$x_i\not = 0 \Rightarrow x_j\not = 0\f$) */
2095  SCIP_HASHMAP* implhash, /**< hash map from variable to node in implication graph */
2096  SCIP_Bool** adjacencymatrix, /**< adjacencymatrix of the conflict graph (only lower half filled) */
2097  int givennode, /**< node of the conflict graph */
2098  int nonznode, /**< node of the conflict graph that is implied to be nonzero if given node is nonzero */
2099  SCIP_Real* impllbs, /**< current lower variable bounds if given node is nonzero (update possible) */
2100  SCIP_Real* implubs, /**< current upper variable bounds if given node is nonzero (update possible) */
2101  SCIP_Bool* implnodes, /**< indicates which variables are currently implied to be nonzero if given node is nonzero (update possible) */
2102  int* naddconss, /**< pointer to store number of added SOS1 constraints */
2103  int* probingdepth, /**< pointer to store current probing depth */
2104  SCIP_Bool* infeasible /**< pointer to store whether the subproblem gets infeasible if variable to 'nonznode' is nonzero */
2105  )
2106 {
2107  SCIP_SUCCDATA** succdatas;
2108  int succnode;
2109  int* succ;
2110  int nsucc;
2111  int s;
2112
2113  assert( nonznode >= 0 && nonznode < SCIPdigraphGetNNodes(conflictgraph) );
2114
2115  /* check probing depth */
2116  if ( conshdlrdata->depthimplanalysis >= 0 && *probingdepth >= conshdlrdata->depthimplanalysis )
2117  return SCIP_OKAY;
2118  ++(*probingdepth);
2119
2120  /* get successors of 'nonznode' in the conflict graph */
2121  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, nonznode);
2122  succ = SCIPdigraphGetSuccessors(conflictgraph, nonznode);
2123
2124  /* loop through neighbors of 'nonznode' in the conflict graph; these variables are implied to be zero */
2125  for (s = 0; s < nsucc; ++s)
2126  {
2127  succnode = succ[s];
2128
2129  /* if the current variable domain of the successor node does not contain the value zero then return that the problem is infeasible
2130  * else if 'succnode' is not already complementary to 'givennode' then add a new complementarity constraint */
2131  if ( givennode == succnode || SCIPisFeasPositive(scip, impllbs[succnode]) || SCIPisFeasNegative(scip, implubs[succnode]) )
2132  {
2133  *infeasible = TRUE;
2134  return SCIP_OKAY;
2135  }
2136  else if ( ! isConnectedSOS1(adjacencymatrix, NULL, givennode, succnode) )
2137  {
2138  char namesos[SCIP_MAXSTRLEN];
2139  SCIP_CONS* soscons = NULL;
2140  SCIP_VAR* var1;
2141  SCIP_VAR* var2;
2142
2143  /* update implied bounds of succnode */
2144  impllbs[succnode] = 0;
2145  implubs[succnode] = 0;
2146
2147  /* add arcs to the conflict graph */
2148  SCIP_CALL( SCIPdigraphAddArcSafe(conflictgraph, givennode, succnode, NULL) );
2149  SCIP_CALL( SCIPdigraphAddArcSafe(conflictgraph, succnode, givennode, NULL) );
2150
2151  /* resort successors */
2152  SCIPsortInt(SCIPdigraphGetSuccessors(conflictgraph, givennode), SCIPdigraphGetNSuccessors(conflictgraph, givennode));
2153  SCIPsortInt(SCIPdigraphGetSuccessors(conflictgraph, succnode), SCIPdigraphGetNSuccessors(conflictgraph, succnode));
2154
2156  if ( givennode > succnode )
2158  else
2160
2161  var1 = SCIPnodeGetVarSOS1(conflictgraph, givennode);
2162  var2 = SCIPnodeGetVarSOS1(conflictgraph, succnode);
2163
2164  /* create SOS1 constraint */
2165  assert( SCIPgetDepth(scip) == 0 );
2166  (void) SCIPsnprintf(namesos, SCIP_MAXSTRLEN, "presolved_sos1_%s_%s", SCIPvarGetName(var1), SCIPvarGetName(var2) );
2167  SCIP_CALL( SCIPcreateConsSOS1(scip, &soscons, namesos, 0, NULL, NULL, TRUE, TRUE, TRUE, FALSE, TRUE,
2168  FALSE, FALSE, FALSE, FALSE) );
2169
2170  /* add variables to SOS1 constraint */
2171  SCIP_CALL( addVarSOS1(scip, soscons, conshdlrdata, var1, 1.0) );
2172  SCIP_CALL( addVarSOS1(scip, soscons, conshdlrdata, var2, 2.0) );
2173
2176
2177  /* release constraint */
2178  SCIP_CALL( SCIPreleaseCons(scip, &soscons) );
2179
2181  }
2182  }
2183
2184  /* by construction: nodes of SOS1 variables are equal for conflict graph and implication graph */
2185  assert( nonznode == SCIPhashmapGetImageInt(implhash, SCIPnodeGetVarSOS1(conflictgraph, nonznode)) );
2186  succdatas = (SCIP_SUCCDATA**) SCIPdigraphGetSuccessorsData(implgraph, nonznode);
2187  nsucc = SCIPdigraphGetNSuccessors(implgraph, nonznode);
2188  succ = SCIPdigraphGetSuccessors(implgraph, nonznode);
2189
2190  /* go further in implication graph */
2191  for (s = 0; s < nsucc; ++s)
2192  {
2193  SCIP_SUCCDATA* data;
2194  int oldprobingdepth;
2195
2196  succnode = succ[s];
2197  data = succdatas[s];
2198  oldprobingdepth = *probingdepth;
2199
2200  /* if current lower bound is smaller than implied lower bound */
2201  if ( SCIPisFeasLT(scip, impllbs[succnode], data->lbimpl) )
2202  {
2203  impllbs[succnode] = data->lbimpl;
2204
2205  /* if node is SOS1 and implied to be nonzero for the first time, then this recursively may imply further bound changes */
2206  if ( varGetNodeSOS1(conshdlrdata, totalvars[succnode]) >= 0 && ! implnodes[succnode] && SCIPisFeasPositive(scip, data->lbimpl) )
2207  {
2208  /* by construction: nodes of SOS1 variables are equal for conflict graph and implication graph */
2209  assert( succnode == SCIPhashmapGetImageInt(implhash, SCIPnodeGetVarSOS1(conflictgraph, succnode)) );
2210  implnodes[succnode] = TRUE; /* in order to avoid cycling */
2211  SCIP_CALL( performImplicationGraphAnalysis(scip, conshdlrdata, conflictgraph, totalvars, implgraph, implhash, adjacencymatrix, givennode, succnode, impllbs, implubs, implnodes, naddconss, probingdepth, infeasible) );
2212  *probingdepth = oldprobingdepth;
2213
2214  /* return if the subproblem is known to be infeasible */
2215  if ( *infeasible )
2216  return SCIP_OKAY;
2217  }
2218  }
2219
2220  /* if current upper bound is larger than implied upper bound */
2221  if ( SCIPisFeasGT(scip, implubs[succnode], data->ubimpl) )
2222  {
2223  implubs[succnode] = data->ubimpl;
2224
2225  /* if node is SOS1 and implied to be nonzero for the first time, then this recursively may imply further bound changes */
2226  if ( varGetNodeSOS1(conshdlrdata, totalvars[succnode]) >= 0 && ! implnodes[succnode] && SCIPisFeasNegative(scip, data->ubimpl) )
2227  {
2228  /* by construction: nodes of SOS1 variables are equal for conflict graph and implication graph */
2229  assert( succnode == SCIPhashmapGetImageInt(implhash, SCIPnodeGetVarSOS1(conflictgraph, succnode)) );
2230  implnodes[succnode] = TRUE; /* in order to avoid cycling */
2231  SCIP_CALL( performImplicationGraphAnalysis(scip, conshdlrdata, conflictgraph, totalvars, implgraph, implhash, adjacencymatrix, givennode, succnode, impllbs, implubs, implnodes, naddconss, probingdepth, infeasible) );
2232  *probingdepth = oldprobingdepth;
2233
2234  /* return if the subproblem is known to be infeasible */
2235  if ( *infeasible )
2236  return SCIP_OKAY;
2237  }
2238  }
2239  }
2240
2241  return SCIP_OKAY;
2242 }
2243
2244
2245 /** returns whether node is implied to be zero; this information is taken from the input array 'implnodes' */
2246 static
2248  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
2249  SCIP_Bool* implnodes, /**< implnodes[i] = TRUE if the SOS1 variable corresponding to node i in the implication graph is implied to be nonzero */
2250  int node /**< node of the conflict graph (or -1) */
2251  )
2252 {
2253  int* succ;
2254  int nsucc;
2255  int s;
2256
2257  if ( node < 0 )
2258  return FALSE;
2259
2260  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, node);
2261  succ = SCIPdigraphGetSuccessors(conflictgraph, node);
2262
2263  /* check whether any successor is implied to be nonzero */
2264  for (s = 0; s < nsucc; ++s)
2265  {
2266  if ( implnodes[succ[s]] )
2267  return TRUE;
2268  }
2269
2270  return FALSE;
2271 }
2272
2273
2274 /** updates arc data of implication graph */
2275 static
2277  SCIP* scip, /**< SCIP pointer */
2278  SCIP_DIGRAPH* implgraph, /**< implication graph */
2279  SCIP_HASHMAP* implhash, /**< hash map from variable to node in implication graph */
2280  SCIP_VAR** totalvars, /**< problem and SOS1 variables */
2281  SCIP_VAR* varv, /**< variable that is assumed to be nonzero */
2282  SCIP_VAR* varw, /**< implication variable */
2283  SCIP_Real lb, /**< old lower bound of \f$x_w\f$ */
2284  SCIP_Real ub, /**< old upper bound of \f$x_w\f$ */
2285  SCIP_Real newbound, /**< new bound of \f$x_w\f$ */
2286  SCIP_Bool lower, /**< whether to consider lower bound implication (otherwise upper bound) */
2287  int* nchgbds, /**< pointer to store number of changed bounds */
2288  SCIP_Bool* update, /**< pointer to store whether implication graph has been updated */
2289  SCIP_Bool* infeasible /**< pointer to store whether an infeasibility has been detected */
2290  )
2291 {
2292  SCIP_SUCCDATA** succdatas;
2293  SCIP_SUCCDATA* data = NULL;
2294  int nsucc;
2295  int* succ;
2296  int indv;
2297  int indw;
2298  int s;
2299
2300  assert( scip != NULL );
2301  assert( implgraph != NULL );
2302  assert( implhash != NULL );
2303  assert( totalvars != NULL );
2304  assert( varv != NULL );
2305  assert( varw != NULL );
2306
2307  /* if x_v != 0 turns out to be infeasible then fix x_v = 0 */
2308  if ( ( lower && SCIPisFeasLT(scip, ub, newbound) ) || ( ! lower && SCIPisFeasGT(scip, lb, newbound) ) )
2309  {
2310  SCIP_Bool infeasible1;
2311  SCIP_Bool infeasible2;
2312  SCIP_Bool tightened1;
2313  SCIP_Bool tightened2;
2314
2315  SCIP_CALL( SCIPtightenVarLb(scip, varv, 0.0, FALSE, &infeasible1, &tightened1) );
2316  SCIP_CALL( SCIPtightenVarUb(scip, varv, 0.0, FALSE, &infeasible2, &tightened2) );
2317
2318  if ( infeasible1 || infeasible2 )
2319  {
2320  SCIPdebugMsg(scip, "detected infeasibility while trying to fix variable <%s> to zero\n", SCIPvarGetName(varv));
2321  *infeasible = TRUE;
2322  }
2323
2324  if ( tightened1 || tightened2 )
2325  {
2326  SCIPdebugMsg(scip, "fixed variable %s from lb = %f and ub = %f to 0.0 \n", SCIPvarGetName(varv), lb, ub);
2327  ++(*nchgbds);
2328  }
2329  }
2330
2331  /* get successor information */
2332  indv = SCIPhashmapGetImageInt(implhash, varv); /* get index of x_v in implication graph */
2333  assert( SCIPhashmapGetImageInt(implhash, totalvars[indv]) == indv );
2334  succdatas = (SCIP_SUCCDATA**) SCIPdigraphGetSuccessorsData(implgraph, indv);
2335  nsucc = SCIPdigraphGetNSuccessors(implgraph, indv);
2336  succ = SCIPdigraphGetSuccessors(implgraph, indv);
2337
2338  /* search for nodew in existing successors. If this is the case then check whether the lower implication bound may be updated ... */
2339  indw = SCIPhashmapGetImageInt(implhash, varw);
2340  assert( SCIPhashmapGetImageInt(implhash, totalvars[indw]) == indw );
2341  for (s = 0; s < nsucc; ++s)
2342  {
2343  if ( succ[s] == indw )
2344  {
2345  data = succdatas[s];
2346  assert( data != NULL );
2347  if ( lower && SCIPisFeasLT(scip, data->lbimpl, newbound) )
2348  {
2349  if ( SCIPvarIsIntegral(varw) )
2350  data->lbimpl = SCIPceil(scip, newbound);
2351  else
2352  data->lbimpl = newbound;
2353
2354  *update = TRUE;
2355  SCIPdebugMsg(scip, "updated to implication %s != 0 -> %s >= %f\n", SCIPvarGetName(varv), SCIPvarGetName(varw), newbound);
2356  }
2357  else if ( ! lower && SCIPisFeasGT(scip, data->ubimpl, newbound) )
2358  {
2359  if ( SCIPvarIsIntegral(varw) )
2360  data->ubimpl = SCIPfloor(scip, newbound);
2361  else
2362  data->ubimpl = newbound;
2363
2364  *update = TRUE;
2365  SCIPdebugMsg(scip, "updated to implication %s != 0 -> %s >= %f\n", SCIPvarGetName(varv), SCIPvarGetName(varw), newbound);
2366  }
2367  break;
2368  }
2369  }
2370
2371  /* ..., otherwise if there does not exist an arc between indv and indw already, then create one and add implication */
2372  if ( s == nsucc )
2373  {
2374  assert( data == NULL );
2375  SCIP_CALL( SCIPallocBlockMemory(scip, &data) );
2376  if ( lower )
2377  {
2378  data->lbimpl = newbound;
2379  data->ubimpl = ub;
2380  SCIPdebugMsg(scip, "add implication %s != 0 -> %s >= %f\n", SCIPvarGetName(varv), SCIPvarGetName(varw), newbound);
2381  }
2382  else
2383  {
2384  data->lbimpl = lb;
2385  data->ubimpl = newbound;
2386  SCIPdebugMsg(scip, "add implication %s != 0 -> %s <= %f\n", SCIPvarGetName(varv), SCIPvarGetName(varw), newbound);
2387  }
2388  SCIP_CALL( SCIPdigraphAddArc(implgraph, indv, indw, (void*)data) );
2389  *update = TRUE;
2390  }
2391
2392  return SCIP_OKAY;
2393 }
2394
2395
2397  *
2398  * Assume the variable from the input is nonzero. If this implies that some other variable is also nonzero, then
2399  * store this information in an implication graph
2400  */
2401 static
2403  SCIP* scip, /**< SCIP pointer */
2404  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
2405  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
2406  SCIP_Bool** adjacencymatrix, /**< adjacency matrix of conflict graph (lower half) */
2407  SCIP_DIGRAPH* implgraph, /**< implication graph (@p j is successor of @p i if and only if \f$x_i\not = 0 \Rightarrow x_j\not = 0\f$) */
2408  SCIP_HASHMAP* implhash, /**< hash map from variable to node in implication graph */
2409  SCIP_Bool* implnodes, /**< implnodes[i] = TRUE if the SOS1 variable corresponding to node i in the implication graph is implied to be nonzero */
2410  SCIP_VAR** totalvars, /**< problem and SOS1 variables */
2411  int** cliquecovers, /**< clique covers of linear constraint */
2412  int* cliquecoversizes, /**< size of clique covers */
2413  int* varincover, /**< array with varincover[i] = cover of SOS1 index @p i */
2414  SCIP_VAR** vars, /**< variables to be checked */
2415  SCIP_Real* coefs, /**< coefficients of variables in linear constraint */
2416  int nvars, /**< number of variables to be checked */
2417  SCIP_Real* bounds, /**< bounds of variables */
2418  SCIP_VAR* var, /**< variable that is assumed to be nonzero */
2419  SCIP_Real bound, /**< bound of variable */
2420  SCIP_Real boundnonzero, /**< bound of variable if it is known to be nonzero if infinity values are not summarized */
2421  int ninftynonzero, /**< number of times infinity/-infinity has to be summarized to boundnonzero */
2422  SCIP_Bool lower, /**< TRUE if lower bounds are consideres; FALSE for upper bounds */
2423  int* nchgbds, /**< pointer to store number of changed bounds */
2424  SCIP_Bool* update, /**< pointer to store whether implication graph has been updated */
2425  SCIP_Bool* infeasible /**< pointer to store whether an infeasibility has been detected */
2426  )
2427 {
2428  int nodev;
2429  int w;
2430
2431  assert( update != NULL );
2432
2433  /* update implication graph if possible */
2434  *update = FALSE;
2435  *infeasible = FALSE;
2436  nodev = varGetNodeSOS1(conshdlrdata, var); /* possibly -1 if var is not involved in an SOS1 constraint */
2437
2438  /* if nodev is an index of an SOS1 variable and at least one lower bound of a variable that is not x_v is infinity */
2439  if ( nodev < 0 || SCIPisInfinity(scip, REALABS(bound)) || ninftynonzero > 1 )
2440  return SCIP_OKAY;
2441
2442  /* for every variable x_w: compute upper bound of a_w * x_w if x_v is known to be nonzero */
2443  for (w = 0; w < nvars; ++w)
2444  {
2445  int newninftynonzero;
2446  SCIP_Bool implinfty = FALSE;
2447  int nodew;
2448
2449  /* get node of x_w in conflict graph: nodew = -1 if it is no SOS1 variable */
2450  nodew = varGetNodeSOS1(conshdlrdata, vars[w]);
2451
2452  newninftynonzero = ninftynonzero;
2453
2454  /* variable should not be fixed to be already zero (note x_v is fixed to be nonzero by assumption) */
2455  if ( nodew < 0 || ( nodev != nodew && ! isConnectedSOS1(adjacencymatrix, NULL, nodev, nodew) && ! isImpliedZero(conflictgraph, implnodes, nodew) ) )
2456  {
2457  SCIP_Real implbound;
2458  SCIP_Bool implcoverw;
2459  int nodecliq;
2460  int indcliq;
2461  int ind;
2462  int j;
2463
2464  /* boundnonzero is the bound of x_v if x_v is nonzero we use this information to get a bound of x_w if x_v is
2465  * nonzero; therefore, we have to perform some recomputations */
2466  implbound = boundnonzero - bound;
2467  ind = varincover[w];
2468  assert( cliquecoversizes[ind] > 0 );
2469
2470  implcoverw = FALSE;
2471  for (j = 0; j < cliquecoversizes[ind]; ++j)
2472  {
2473  indcliq = cliquecovers[ind][j];
2474  assert( 0 <= indcliq && indcliq < nvars );
2475
2476  nodecliq = varGetNodeSOS1(conshdlrdata, vars[indcliq]); /* possibly -1 if variable is not involved in an SOS1 constraint */
2477
2478  /* if nodecliq is not a member of an SOS1 constraint or the variable corresponding to nodecliq is not implied to be zero if x_v != 0 */
2479  if ( nodecliq < 0 || (! isConnectedSOS1(adjacencymatrix, NULL, nodev, nodecliq) && ! isImpliedZero(conflictgraph, implnodes, nodecliq) ) )
2480  {
2481  if ( indcliq == w )
2482  {
2483  if ( !SCIPisInfinity(scip, REALABS(bounds[w])) && !SCIPisInfinity(scip, REALABS(implbound + bounds[w])) )
2484  implbound += bounds[w];
2485  else
2486  --newninftynonzero;
2487  implcoverw = TRUE;
2488  }
2489  else if ( implcoverw )
2490  {
2491  if ( SCIPisInfinity(scip, REALABS(bounds[indcliq])) || SCIPisInfinity(scip, REALABS(implbound - bounds[indcliq])) )
2492  implinfty = TRUE;
2493  else
2494  implbound -= bounds[indcliq];
2495  break;
2496  }
2497  else
2498  {
2499  if ( SCIPisInfinity(scip, REALABS(bounds[indcliq])) )
2500  implinfty = TRUE;
2501  break;
2502  }
2503  }
2504  }
2505
2506  /* check whether x_v != 0 implies a bound change of x_w */
2507  if ( ! implinfty && newninftynonzero == 0 )
2508  {
2509  SCIP_Real newbound;
2510  SCIP_Real coef;
2511  SCIP_Real lb;
2512  SCIP_Real ub;
2513
2514  lb = SCIPvarGetLbLocal(vars[w]);
2515  ub = SCIPvarGetUbLocal(vars[w]);
2516  coef = coefs[w];
2517
2518  if ( SCIPisFeasZero(scip, coef) )
2519  continue;
2520
2521  newbound = implbound / coef;
2522
2523  if ( SCIPisInfinity(scip, newbound) )
2524  continue;
2525
2526  /* check if an implication can be added/updated or assumption x_v != 0 is infeasible */
2527  if ( lower )
2528  {
2529  if ( SCIPisFeasPositive(scip, coef) && SCIPisFeasLT(scip, lb, newbound) )
2530  {
2531  SCIP_CALL( updateArcData(scip, implgraph, implhash, totalvars, var, vars[w], lb, ub, newbound, TRUE, nchgbds, update, infeasible) );
2532  }
2533  else if ( SCIPisFeasNegative(scip, coef) && SCIPisFeasGT(scip, ub, newbound) )
2534  {
2535  SCIP_CALL( updateArcData(scip, implgraph, implhash, totalvars, var, vars[w], lb, ub, newbound, FALSE, nchgbds, update, infeasible) );
2536  }
2537  }
2538  else
2539  {
2540  if ( SCIPisFeasPositive(scip, coef) && SCIPisFeasGT(scip, ub, newbound) )
2541  {
2542  SCIP_CALL( updateArcData(scip, implgraph, implhash, totalvars, var, vars[w], lb, ub, newbound, FALSE, nchgbds, update, infeasible) );
2543  }
2544  else if ( SCIPisFeasNegative(scip, coef) && SCIPisFeasLT(scip, lb, newbound) )
2545  {
2546  SCIP_CALL( updateArcData(scip, implgraph, implhash, totalvars, var, vars[w], lb, ub, newbound, TRUE, nchgbds, update, infeasible) );
2547  }
2548  }
2549  }
2550  }
2551  }
2552
2553  return SCIP_OKAY;
2554 }
2555
2556
2557 /** search new disjoint clique that covers given node
2558  *
2559  * For a given vertex @p v search for a clique of the conflict graph induced by the variables of a linear constraint that
2560  * - covers @p v and
2561  * - has an an empty intersection with already computed clique cover.
2562  */
2563 static
2565  SCIP* scip, /**< SCIP pointer */
2566  SCIP_DIGRAPH* conflictgraphroot, /**< conflict graph of the root node (nodes: 1, ..., @p nsos1vars) */
2567  SCIP_DIGRAPH* conflictgraphlin, /**< conflict graph of linear constraint (nodes: 1, ..., @p nlinvars) */
2568  SCIP_VAR** linvars, /**< variables in linear constraint */
2569  SCIP_Bool* coveredvars, /**< states which variables of the linear constraint are currently covered by a clique */
2570  int* clique, /**< array to store new clique in cover */
2571  int* cliquesize, /**< pointer to store the size of @p clique */
2572  int v, /**< position of variable in linear constraint that should be covered */
2573  SCIP_Bool considersolvals /**< TRUE if largest auxiliary bigM values of variables should be prefered */
2574  )
2575 {
2576  int nsucc;
2577  int s;
2578
2579  assert( conflictgraphlin != NULL );
2580  assert( linvars != NULL );
2581  assert( coveredvars != NULL );
2582  assert( clique != NULL );
2583  assert( cliquesize != NULL );
2584
2585  assert( ! coveredvars[v] ); /* we should produce a new clique */
2586
2587  /* add index 'v' to the clique cover */
2588  clique[0] = v;
2589  *cliquesize = 1;
2590
2591  nsucc = SCIPdigraphGetNSuccessors(conflictgraphlin, v);
2592  if ( nsucc > 0 )
2593  {
2594  int* extensions;
2595  int nextensions = 0;
2596  int nextensionsnew;
2597  int succnode;
2598  int* succ;
2599
2600  /* allocate buffer array */
2601  SCIP_CALL( SCIPallocBufferArray(scip, &extensions, nsucc) );
2602
2603  succ = SCIPdigraphGetSuccessors(conflictgraphlin, v);
2604
2605  /* compute possible extensions for the clique cover */
2606  for (s = 0; s < nsucc; ++s)
2607  {
2608  succnode = succ[s];
2609  if ( ! coveredvars[succnode] )
2610  extensions[nextensions++] = succ[s];
2611  }
2612
2613  /* while there exist possible extensions for the clique cover */
2614  while ( nextensions > 0 )
2615  {
2616  int bestindex = -1;
2617
2618  if ( considersolvals )
2619  {
2620  SCIP_Real bestbigMval;
2621  SCIP_Real bigMval;
2622
2623  bestbigMval = -SCIPinfinity(scip);
2624
2625  /* search for the extension with the largest absolute value of its LP relaxation solution value */
2626  for (s = 0; s < nextensions; ++s)
2627  {
2628  bigMval = nodeGetSolvalBinaryBigMSOS1(scip, conflictgraphroot, NULL, extensions[s]);
2629  if ( SCIPisFeasLT(scip, bestbigMval, bigMval) )
2630  {
2631  bestbigMval = bigMval;
2632  bestindex = extensions[s];
2633  }
2634  }
2635  }
2636  else
2637  bestindex = extensions[0];
2638
2639  assert( bestindex != -1 );
2640
2641  /* add bestindex to the clique cover */
2642  clique[(*cliquesize)++] = bestindex;
2643
2644  /* compute new 'extensions' array */
2645  nextensionsnew = 0;
2646  for (s = 0; s < nextensions; ++s)
2647  {
2648  if ( s != bestindex && isConnectedSOS1(NULL, conflictgraphlin, bestindex, extensions[s]) )
2649  extensions[nextensionsnew++] = extensions[s];
2650  }
2651  nextensions = nextensionsnew;
2652  }
2653
2654  /* free buffer array */
2655  SCIPfreeBufferArray(scip, &extensions);
2656  }
2657
2658  /* mark covered indices */
2659  for (s = 0; s < *cliquesize; ++s)
2660  {
2661  int ind;
2662
2663  ind = clique[s];
2664  assert( 0 <= ind );
2665  assert( ! coveredvars[ind] );
2666  coveredvars[ind] = TRUE;
2667  }
2668
2669  return SCIP_OKAY;
2670 }
2671
2672
2673 /** try to tighten upper and lower bounds for variables */
2674 static
2676  SCIP* scip, /**< SCIP pointer */
2677  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
2678  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
2679  SCIP_DIGRAPH* implgraph, /**< implication graph (@p j is successor of @p i if and only if \f$x_i\not = 0 \f$ implies a new lower/upper bound for \f$x_j\f$) */
2680  SCIP_HASHMAP* implhash, /**< hash map from variable to node in implication graph */
2682  SCIP_VAR** totalvars, /**< problem and SOS1 vars */
2683  int ntotalvars, /**< number of problem and SOS1 variables*/
2684  int nsos1vars, /**< number of SOS1 variables */
2685  int* nchgbds, /**< pointer to store number of changed bounds */
2686  SCIP_Bool* implupdate, /**< pointer to store whether the implication graph has been updated in this function call */
2687  SCIP_Bool* cutoff /**< pointer to store if current nodes LP is infeasible */
2688  )
2689 {
2690  SCIP_CONSHDLR* conshdlrlinear;
2691  SCIP_CONS** linearconss;
2692  int nlinearconss;
2693
2694  SCIP_Bool* implnodes = NULL; /* implnodes[i] = TRUE if the SOS1 variable corresponding to node i in the implication graph is implied to be nonzero */
2695  SCIP_Bool* coveredvars = NULL; /* coveredvars[i] = TRUE if variable with index i is covered by the clique cover */
2696  int* varindincons = NULL; /* varindincons[i] = position of SOS1 index i in linear constraint (-1 if x_i is not involved in linear constraint) */
2697
2698  SCIP_VAR** trafolinvars = NULL; /* variables of transformed linear constraints without (multi)aggregated variables */
2699  int ntrafolinvars = 0;
2700  SCIP_Real* trafolinvals = NULL;
2701  SCIP_Real* trafoubs = NULL;
2702  SCIP_Real* trafolbs = NULL;
2703  SCIP_Real traforhs;
2704  SCIP_Real trafolhs;
2705
2706  SCIP_VAR** sos1linvars = NULL; /* variables that are not contained in linear constraint, but are in conflict with a variable from the linear constraint */
2707  int nsos1linvars;
2708  int c;
2709
2710  assert( scip != NULL );
2711  assert( conflictgraph != NULL );
2712  assert( adjacencymatrix != NULL );
2713  assert( nchgbds != NULL );
2714  assert( cutoff != NULL );
2715
2716  *cutoff = FALSE;
2717  *implupdate = FALSE;
2718
2719  /* get constraint handler data of linear constraints */
2720  conshdlrlinear = SCIPfindConshdlr(scip, "linear");
2721  if ( conshdlrlinear == NULL )
2722  return SCIP_OKAY;
2723
2724  /* get linear constraints and number of linear constraints */
2725  nlinearconss = SCIPconshdlrGetNConss(conshdlrlinear);
2726  linearconss = SCIPconshdlrGetConss(conshdlrlinear);
2727
2728  /* allocate buffer arrays */
2729  SCIP_CALL( SCIPallocBufferArray(scip, &sos1linvars, nsos1vars) );
2730  SCIP_CALL( SCIPallocBufferArray(scip, &implnodes, nsos1vars) );
2731  SCIP_CALL( SCIPallocBufferArray(scip, &varindincons, nsos1vars) );
2732  SCIP_CALL( SCIPallocBufferArray(scip, &coveredvars, ntotalvars) );
2733  SCIP_CALL( SCIPallocBufferArray(scip, &trafoubs, ntotalvars) );
2734  SCIP_CALL( SCIPallocBufferArray(scip, &trafolbs, ntotalvars) );
2735
2736  /* for every linear constraint and every SOS1 variable */
2737  for (c = 0; c < nlinearconss + nsos1vars && ! (*cutoff); ++c)
2738  {
2739  SCIP_DIGRAPH* conflictgraphlin;
2740  int** cliquecovers = NULL; /* clique covers of indices of variables in linear constraint */
2741  int* cliquecoversizes = NULL; /* size of each cover */
2742  SCIP_VAR* sosvar = NULL;
2743  SCIP_Real* cliquecovervals = NULL;
2744  SCIP_Real constant;
2745  int* varincover = NULL; /* varincover[i] = cover of SOS1 index i */
2746  int ncliquecovers;
2747  int requiredsize;
2748
2749  int v;
2750  int i;
2751  int j;
2752
2753  /* get transformed linear constraints (without aggregated variables) */
2754  if ( c < nlinearconss )
2755  {
2756  SCIP_VAR** origlinvars;
2757  SCIP_Real* origlinvals;
2758
2759  /* get data of linear constraint */
2760  ntrafolinvars = SCIPgetNVarsLinear(scip, linearconss[c]);
2761  if ( ntrafolinvars < 1 )
2762  continue;
2763
2764  origlinvars = SCIPgetVarsLinear(scip, linearconss[c]);
2765  origlinvals = SCIPgetValsLinear(scip, linearconss[c]);
2766  assert( origlinvars != NULL );
2767  assert( origlinvals != NULL );
2768
2769  /* copy variables and coefficients of linear constraint */
2770  SCIP_CALL( SCIPduplicateBufferArray(scip, &trafolinvars, origlinvars, ntrafolinvars) );
2771  SCIP_CALL( SCIPduplicateBufferArray(scip, &trafolinvals, origlinvals, ntrafolinvars) );
2772
2773  trafolhs = SCIPgetLhsLinear(scip, linearconss[c]);
2774  traforhs = SCIPgetRhsLinear(scip, linearconss[c]);
2775  }
2776  else
2777  {
2778  sosvar = SCIPnodeGetVarSOS1(conflictgraph, c - nlinearconss);
2779
2783  continue;
2784
2785  /* store variable so it will be transformed to active variables below */
2786  ntrafolinvars = 1;
2787  SCIP_CALL( SCIPallocBufferArray(scip, &trafolinvars, ntrafolinvars + 1) );
2788  SCIP_CALL( SCIPallocBufferArray(scip, &trafolinvals, ntrafolinvars + 1) );
2789
2790  trafolinvars[0] = sosvar;
2791  trafolinvals[0] = 1.0;
2792
2793  trafolhs = 0.0;
2794  traforhs = 0.0;
2795  }
2796  assert( ntrafolinvars >= 1 );
2797
2798  /* transform linear constraint */
2799  constant = 0.0;
2800  SCIP_CALL( SCIPgetProbvarLinearSum(scip, trafolinvars, trafolinvals, &ntrafolinvars, ntrafolinvars, &constant, &requiredsize, TRUE) );
2801  if( requiredsize > ntrafolinvars )
2802  {
2803  SCIP_CALL( SCIPreallocBufferArray(scip, &trafolinvars, requiredsize + 1) );
2804  SCIP_CALL( SCIPreallocBufferArray(scip, &trafolinvals, requiredsize + 1) );
2805
2806  SCIP_CALL( SCIPgetProbvarLinearSum(scip, trafolinvars, trafolinvals, &ntrafolinvars, requiredsize, &constant, &requiredsize, TRUE) );
2807  assert( requiredsize <= ntrafolinvars );
2808  }
2809  if( !SCIPisInfinity(scip, -trafolhs) )
2810  trafolhs -= constant;
2811  if( !SCIPisInfinity(scip, traforhs) )
2812  traforhs -= constant;
2813
2814  if ( ntrafolinvars == 0 )
2815  {
2816  SCIPfreeBufferArray(scip, &trafolinvals);
2817  SCIPfreeBufferArray(scip, &trafolinvars);
2818  continue;
2819  }
2820
2821  /* possibly add sos1 variable to create aggregation/multiaggregation/negation equality */
2822  if ( sosvar != NULL )
2823  {
2824  trafolinvals[ntrafolinvars] = -1.0;
2825  trafolinvars[ntrafolinvars] = sosvar;
2826  ++ntrafolinvars;
2827  }
2828
2829  /* compute lower and upper bounds of each term a_i * x_i of transformed constraint */
2830  for (v = 0; v < ntrafolinvars; ++v)
2831  {
2832  SCIP_Real lb;
2833  SCIP_Real ub;
2834
2835  lb = SCIPvarGetLbLocal(trafolinvars[v]);
2836  ub = SCIPvarGetUbLocal(trafolinvars[v]);
2837
2838  if ( trafolinvals[v] < 0.0 )
2839  SCIPswapReals(&lb, &ub);
2840
2841  assert( ! SCIPisInfinity(scip, REALABS(trafolinvals[v])) );
2842
2843  if ( SCIPisInfinity(scip, REALABS(lb)) || SCIPisInfinity(scip, REALABS(lb * trafolinvals[v])) )
2844  trafolbs[v] = -SCIPinfinity(scip);
2845  else
2846  trafolbs[v] = lb * trafolinvals[v];
2847
2848  if ( SCIPisInfinity(scip, REALABS(ub)) || SCIPisInfinity(scip, REALABS(ub * trafolinvals[v])) )
2849  trafoubs[v] = SCIPinfinity(scip);
2850  else
2851  trafoubs[v] = ub * trafolinvals[v];
2852  }
2853
2854  /* initialization: mark all the SOS1 variables as 'not a member of the linear constraint' */
2855  for (v = 0; v < nsos1vars; ++v)
2856  varindincons[v] = -1;
2857
2858  /* save position of SOS1 variables in linear constraint */
2859  for (v = 0; v < ntrafolinvars; ++v)
2860  {
2861  int node;
2862
2863  node = varGetNodeSOS1(conshdlrdata, trafolinvars[v]);
2864
2865  if ( node >= 0 )
2866  varindincons[node] = v;
2867  }
2868
2869  /* create conflict graph of linear constraint */
2870  SCIP_CALL( SCIPcreateDigraph(scip, &conflictgraphlin, ntrafolinvars) );
2871  SCIP_CALL( genConflictgraphLinearCons(conshdlrdata, conflictgraphlin, conflictgraph, trafolinvars, ntrafolinvars, varindincons) );
2872
2873  /* mark all the variables as 'not covered by some clique cover' */
2874  for (i = 0; i < ntrafolinvars; ++i)
2875  coveredvars[i] = FALSE;
2876
2877  /* allocate buffer array */
2878  SCIP_CALL( SCIPallocBufferArray(scip, &cliquecovervals, ntrafolinvars) );
2879  SCIP_CALL( SCIPallocBufferArray(scip, &cliquecoversizes, ntrafolinvars) );
2880  SCIP_CALL( SCIPallocBufferArray(scip, &cliquecovers, ntrafolinvars) );
2881
2882  /* compute distinct cliques that cover all the variables of the linear constraint */
2883  ncliquecovers = 0;
2884  for (v = 0; v < ntrafolinvars; ++v)
2885  {
2886  /* if variable is not already covered by an already known clique cover */
2887  if ( ! coveredvars[v] )
2888  {
2889  SCIP_CALL( SCIPallocBufferArray(scip, &(cliquecovers[ncliquecovers]), ntrafolinvars) ); /*lint !e866*/
2890  SCIP_CALL( computeVarsCoverSOS1(scip, conflictgraph, conflictgraphlin, trafolinvars, coveredvars, cliquecovers[ncliquecovers], &(cliquecoversizes[ncliquecovers]), v, FALSE) );
2891  ++ncliquecovers;
2892  }
2893  }
2894
2895  /* free conflictgraph */
2896  SCIPdigraphFree(&conflictgraphlin);
2897
2898  /* compute variables that are not contained in transformed linear constraint, but are in conflict with a variable from the transformed linear constraint */
2899  nsos1linvars = 0;
2900  for (v = 0; v < ntrafolinvars; ++v)
2901  {
2902  int nodev;
2903
2904  nodev = varGetNodeSOS1(conshdlrdata, trafolinvars[v]);
2905
2906  /* if variable is an SOS1 variable */
2907  if ( nodev >= 0 )
2908  {
2909  int succnode;
2910  int nsucc;
2911  int* succ;
2912  int s;
2913
2914  succ = SCIPdigraphGetSuccessors(conflictgraph, nodev);
2915  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, nodev);
2916
2917  for (s = 0; s < nsucc; ++s)
2918  {
2919  succnode = succ[s];
2920
2921  /* if variable is not a member of linear constraint and not already listed in the array sos1linvars */
2922  if ( varindincons[succnode] == -1 )
2923  {
2924  sos1linvars[nsos1linvars] = SCIPnodeGetVarSOS1(conflictgraph, succnode);
2925  varindincons[succnode] = -2; /* mark variable as listed in array sos1linvars */
2926  ++nsos1linvars;
2927  }
2928  }
2929  }
2930  }
2931
2932  /* try to tighten lower bounds */
2933
2934  /* sort each cliquecover array in ascending order of the lower bounds of a_i * x_i; fill vector varincover */
2935  SCIP_CALL( SCIPallocBufferArray(scip, &varincover, ntrafolinvars) );
2936  for (i = 0; i < ncliquecovers; ++i)
2937  {
2938  for (j = 0; j < cliquecoversizes[i]; ++j)
2939  {
2940  int ind = cliquecovers[i][j];
2941
2942  varincover[ind] = i;
2943  cliquecovervals[j] = trafoubs[ind];
2944  }
2945  SCIPsortDownRealInt(cliquecovervals, cliquecovers[i], cliquecoversizes[i]);
2946  }
2947
2948  /* for every variable in transformed constraint: try lower bound tightening */
2949  for (v = 0; v < ntrafolinvars + nsos1linvars; ++v)
2950  {
2951  SCIP_Real newboundnonzero; /* new bound of a_v * x_v if we assume that x_v != 0 */
2952  SCIP_Real newboundnores; /* new bound of a_v * x_v if we assume that x_v = 0 is possible */
2953  SCIP_Real newbound; /* resulting new bound of x_v */
2954  SCIP_VAR* var;
2955  SCIP_Real trafoubv;
2956  SCIP_Real linval;
2957  SCIP_Real ub;
2958  SCIP_Real lb;
2959  SCIP_Bool tightened;
2960  SCIP_Bool infeasible;
2961  SCIP_Bool inftynores = FALSE;
2962  SCIP_Bool update;
2963  int ninftynonzero = 0;
2964  int nodev;
2965  int w;
2966
2967  if ( v < ntrafolinvars )
2968  {
2969  var = trafolinvars[v];
2970  trafoubv = trafoubs[v];
2971  }
2972  else
2973  {
2974  assert( v >= ntrafolinvars );
2975  var = sos1linvars[v-ntrafolinvars];/*lint !e679*/
2976  trafoubv = 0.0;
2977  }
2978
2979  ub = SCIPvarGetUbLocal(var);
2980  lb = SCIPvarGetLbLocal(var);
2981
2982  if ( SCIPisInfinity(scip, -trafolhs) || SCIPisZero(scip, ub - lb) )
2983  continue;
2984
2985  newboundnonzero = trafolhs;
2986  newboundnores = trafolhs;
2987  nodev = varGetNodeSOS1(conshdlrdata, var); /* possibly -1 if var is not involved in an SOS1 constraint */
2988  assert( nodev < nsos1vars );
2989
2990  /* determine incidence vector of implication variables */
2991  for (w = 0; w < nsos1vars; ++w)
2992  implnodes[w] = FALSE;
2993  SCIP_CALL( getSOS1Implications(scip, conshdlrdata, totalvars, implgraph, implhash, implnodes, SCIPhashmapGetImageInt(implhash, var)) );
2994
2995  /* compute new bound */
2996  for (i = 0; i < ncliquecovers; ++i)
2997  {
2998  int indcliq;
2999  int nodecliq;
3000
3001  assert( cliquecoversizes[i] > 0 );
3002
3003  indcliq = cliquecovers[i][0];
3004  assert( 0 <= indcliq && indcliq < ntrafolinvars );
3005
3006  /* determine maximum without index v (note that the array 'cliquecovers' is sorted by the values of trafoub in non-increasing order) */
3007  if ( v != indcliq )
3008  {
3009  if ( SCIPisInfinity(scip, trafoubs[indcliq]) || SCIPisInfinity(scip, REALABS(newboundnores - trafoubs[indcliq])) )
3010  inftynores = TRUE;
3011  else
3012  newboundnores -= trafoubs[indcliq];
3013  }
3014  else if ( cliquecoversizes[i] > 1 )
3015  {
3016  assert( 0 <= cliquecovers[i][1] && cliquecovers[i][1] < ntrafolinvars );
3017  if ( SCIPisInfinity(scip, trafoubs[cliquecovers[i][1]]) || SCIPisInfinity(scip, REALABS(newboundnores - trafoubs[cliquecovers[i][1]])) )
3018  inftynores = TRUE;
3019  else
3020  newboundnores -= trafoubs[cliquecovers[i][1]];/*lint --e{679}*/
3021  }
3022
3023  /* determine maximum without index v and if x_v is nonzero (note that the array 'cliquecovers' is sorted by the values of trafoub in non-increasing order) */
3024  for (j = 0; j < cliquecoversizes[i]; ++j)
3025  {
3026  indcliq = cliquecovers[i][j];
3027  assert( 0 <= indcliq && indcliq < ntrafolinvars );
3028
3029  nodecliq = varGetNodeSOS1(conshdlrdata, trafolinvars[indcliq]); /* possibly -1 if variable is not involved in an SOS1 constraint */
3030  assert( nodecliq < nsos1vars );
3031
3032  if ( v != indcliq )
3033  {
3034  /* if nodev or nodecliq are not a member of an SOS1 constraint or the variable corresponding to nodecliq is not implied to be zero if x_v != 0 */
3035  if ( nodev < 0 || nodecliq < 0 || (! isConnectedSOS1(adjacencymatrix, NULL, nodev, nodecliq) && ! isImpliedZero(conflictgraph, implnodes, nodecliq) ) )
3036  {
3037  if ( SCIPisInfinity(scip, trafoubs[indcliq]) || SCIPisInfinity(scip, REALABS(newboundnonzero - trafoubs[indcliq])) )
3038  ++ninftynonzero;
3039  else
3040  newboundnonzero -= trafoubs[indcliq];
3041  break; /* break since we are only interested in the maximum upper bound among the variables in the clique cover;
3042  * the variables in the clique cover form an SOS1 constraint, thus only one of them can be nonzero */
3043  }
3044  }
3045  }
3046  }
3047  assert( ninftynonzero == 0 || inftynores );
3048
3049  /* if computed upper bound is not infinity and variable is contained in linear constraint */
3050  if ( ninftynonzero == 0 && v < ntrafolinvars )
3051  {
3052  linval = trafolinvals[v];
3053
3054  if ( SCIPisFeasZero(scip, linval) )
3055  continue;
3056
3057  /* compute new bound */
3058  if ( SCIPisFeasPositive(scip, newboundnores) && ! inftynores )
3059  newbound = newboundnonzero;
3060  else
3061  newbound = MIN(0, newboundnonzero);
3062  newbound /= linval;
3063
3064  if ( SCIPisInfinity(scip, newbound) )
3065  continue;
3066
3067  /* check if new bound is tighter than the old one or problem is infeasible */
3068  if ( SCIPisFeasPositive(scip, linval) && SCIPisFeasLT(scip, lb, newbound) )
3069  {
3070  if ( SCIPisFeasLT(scip, ub, newbound) )
3071  {
3072  *cutoff = TRUE;
3073  break;
3074  }
3075
3076  if ( SCIPvarIsIntegral(var) )
3077  newbound = SCIPceil(scip, newbound);
3078
3079  SCIP_CALL( SCIPtightenVarLb(scip, var, newbound, FALSE, &infeasible, &tightened) );
3080  assert( ! infeasible );
3081
3082  if ( tightened )
3083  {
3084  SCIPdebugMsg(scip, "changed lower bound of variable %s from %f to %f \n", SCIPvarGetName(var), lb, newbound);
3085  ++(*nchgbds);
3086  }
3087  }
3088  else if ( SCIPisFeasNegative(scip, linval) && SCIPisFeasGT(scip, ub, newbound) )
3089  {
3090  /* if assumption a_i * x_i != 0 was not correct */
3091  if ( SCIPisFeasGT(scip, SCIPvarGetLbLocal(var), newbound) )
3092  {
3093  *cutoff = TRUE;
3094  break;
3095  }
3096
3097  if ( SCIPvarIsIntegral(var) )
3098  newbound = SCIPfloor(scip, newbound);
3099
3100  SCIP_CALL( SCIPtightenVarUb(scip, var, newbound, FALSE, &infeasible, &tightened) );
3101  assert( ! infeasible );
3102
3103  if ( tightened )
3104  {
3105  SCIPdebugMsg(scip, "changed upper bound of variable %s from %f to %f \n", SCIPvarGetName(var), ub, newbound);
3106  ++(*nchgbds);
3107  }
3108  }
3109  }
3110
3111  /* update implication graph if possible */
3112  SCIP_CALL( updateImplicationGraphSOS1(scip, conshdlrdata, conflictgraph, adjacencymatrix, implgraph, implhash, implnodes, totalvars, cliquecovers, cliquecoversizes, varincover,
3113  trafolinvars, trafolinvals, ntrafolinvars, trafoubs, var, trafoubv, newboundnonzero, ninftynonzero, TRUE, nchgbds, &update, &infeasible) );
3114  if ( infeasible )
3115  *cutoff = TRUE;
3116  else if ( update )
3117  *implupdate = TRUE;
3118  }
3119
3120  if ( *cutoff == TRUE )
3121  {
3122  /* free memory */
3123  SCIPfreeBufferArrayNull(scip, &varincover);
3124  for (j = ncliquecovers-1; j >= 0; --j)
3125  SCIPfreeBufferArrayNull(scip, &cliquecovers[j]);
3126  SCIPfreeBufferArrayNull(scip, &cliquecovers);
3127  SCIPfreeBufferArrayNull(scip, &cliquecoversizes);
3128  SCIPfreeBufferArrayNull(scip, &cliquecovervals);
3129  SCIPfreeBufferArrayNull(scip, &trafolinvals);
3130  SCIPfreeBufferArrayNull(scip, &trafolinvars);
3131  break;
3132  }
3133
3134  /* try to tighten upper bounds */
3135
3136  /* sort each cliquecover array in ascending order of the lower bounds of a_i * x_i; fill vector varincover */
3137  for (i = 0; i < ncliquecovers; ++i)
3138  {
3139  for (j = 0; j < cliquecoversizes[i]; ++j)
3140  {
3141  int ind = cliquecovers[i][j];
3142
3143  varincover[ind] = i;
3144  cliquecovervals[j] = trafolbs[ind];
3145  }
3146  SCIPsortRealInt(cliquecovervals, cliquecovers[i], cliquecoversizes[i]);
3147  }
3148
3149  /* for every variable that is in transformed constraint or every variable that is in conflict with some variable from trans. cons.:
3150  try upper bound tightening */
3151  for (v = 0; v < ntrafolinvars + nsos1linvars; ++v)
3152  {
3153  SCIP_Real newboundnonzero; /* new bound of a_v*x_v if we assume that x_v != 0 */
3154  SCIP_Real newboundnores; /* new bound of a_v*x_v if there are no restrictions */
3155  SCIP_Real newbound; /* resulting new bound of x_v */
3156  SCIP_VAR* var;
3157  SCIP_Real linval;
3158  SCIP_Real trafolbv;
3159  SCIP_Real lb;
3160  SCIP_Real ub;
3161  SCIP_Bool tightened;
3162  SCIP_Bool infeasible;
3163  SCIP_Bool inftynores = FALSE;
3164  SCIP_Bool update;
3165  int ninftynonzero = 0;
3166  int nodev;
3167  int w;
3168
3169  if ( v < ntrafolinvars )
3170  {
3171  var = trafolinvars[v];
3172  trafolbv = trafolbs[v];
3173  }
3174  else
3175  {
3176  assert( v-ntrafolinvars >= 0 );
3177  var = sos1linvars[v-ntrafolinvars];/*lint !e679*/
3178  trafolbv = 0.0; /* since variable is not a member of linear constraint */
3179  }
3180  lb = SCIPvarGetLbLocal(var);
3181  ub = SCIPvarGetUbLocal(var);
3182  if ( SCIPisInfinity(scip, traforhs) || SCIPisEQ(scip, lb, ub) )
3183  continue;
3184
3185  newboundnonzero = traforhs;
3186  newboundnores = traforhs;
3187  nodev = varGetNodeSOS1(conshdlrdata, var); /* possibly -1 if var is not involved in an SOS1 constraint */
3188  assert( nodev < nsos1vars );
3189
3190  /* determine incidence vector of implication variables (i.e., which SOS1 variables are nonzero if x_v is nonzero) */
3191  for (w = 0; w < nsos1vars; ++w)
3192  implnodes[w] = FALSE;
3193  SCIP_CALL( getSOS1Implications(scip, conshdlrdata, totalvars, implgraph, implhash, implnodes, SCIPhashmapGetImageInt(implhash, var)) );
3194
3195  /* compute new bound */
3196  for (i = 0; i < ncliquecovers; ++i)
3197  {
3198  int indcliq;
3199  int nodecliq;
3200
3201  assert( cliquecoversizes[i] > 0 );
3202
3203  indcliq = cliquecovers[i][0];
3204  assert( 0 <= indcliq && indcliq < ntrafolinvars );
3205
3206  /* determine minimum without index v (note that the array 'cliquecovers' is sorted by the values of trafolb in increasing order) */
3207  if ( v != indcliq )
3208  {
3209  /* if bound would be infinity */
3210  if ( SCIPisInfinity(scip, -trafolbs[indcliq]) || SCIPisInfinity(scip, REALABS(newboundnores - trafolbs[indcliq])) )
3211  inftynores = TRUE;
3212  else
3213  newboundnores -= trafolbs[indcliq];
3214  }
3215  else if ( cliquecoversizes[i] > 1 )
3216  {
3217  assert( 0 <= cliquecovers[i][1] && cliquecovers[i][1] < ntrafolinvars );
3218  if ( SCIPisInfinity(scip, -trafolbs[cliquecovers[i][1]]) || SCIPisInfinity(scip, REALABS(newboundnores - trafolbs[cliquecovers[i][1]])) )
3219  inftynores = TRUE;
3220  else
3221  newboundnores -= trafolbs[cliquecovers[i][1]]; /*lint --e{679}*/
3222  }
3223
3224  /* determine minimum without index v and if x_v is nonzero (note that the array 'cliquecovers' is sorted by the values of trafolb in increasing order) */
3225  for (j = 0; j < cliquecoversizes[i]; ++j)
3226  {
3227  indcliq = cliquecovers[i][j];
3228  assert( 0 <= indcliq && indcliq < ntrafolinvars );
3229
3230  nodecliq = varGetNodeSOS1(conshdlrdata, trafolinvars[indcliq]); /* possibly -1 if variable is not involved in an SOS1 constraint */
3231  assert( nodecliq < nsos1vars );
3232
3233  if ( v != indcliq )
3234  {
3235  /* if nodev or nodecliq are not a member of an SOS1 constraint or the variable corresponding to nodecliq is not implied to be zero if x_v != 0 */
3236  if ( nodev < 0 || nodecliq < 0 || (! isConnectedSOS1(adjacencymatrix, NULL, nodev, nodecliq) && ! isImpliedZero(conflictgraph, implnodes, nodecliq) ) )
3237  {
3238  /* if bound would be infinity */
3239  if ( SCIPisInfinity(scip, -trafolbs[indcliq]) || SCIPisInfinity(scip, REALABS(newboundnonzero - trafolbs[indcliq])) )
3240  ++ninftynonzero;
3241  else
3242  newboundnonzero -= trafolbs[indcliq];
3243  break; /* break since we are only interested in the minimum lower bound among the variables in the clique cover;
3244  * the variables in the clique cover form an SOS1 constraint, thus only one of them can be nonzero */
3245  }
3246  }
3247  }
3248  }
3249  assert( ninftynonzero == 0 || inftynores );
3250
3251  /* if computed bound is not infinity and variable is contained in linear constraint */
3252  if ( ninftynonzero == 0 && v < ntrafolinvars )
3253  {
3254  linval = trafolinvals[v];
3255
3256  if ( SCIPisFeasZero(scip, linval) )
3257  continue;
3258
3259  /* compute new bound */
3260  if ( SCIPisFeasNegative(scip, newboundnores) && ! inftynores )
3261  newbound = newboundnonzero;
3262  else
3263  newbound = MAX(0, newboundnonzero);
3264  newbound /= linval;
3265
3266  if ( SCIPisInfinity(scip, newbound) )
3267  continue;
3268
3269  /* check if new bound is tighter than the old one or problem is infeasible */
3270  if ( SCIPisFeasPositive(scip, linval) && SCIPisFeasGT(scip, ub, newbound) )
3271  {
3272  /* if new upper bound is smaller than the lower bound, we are infeasible */
3273  if ( SCIPisFeasGT(scip, lb, newbound) )
3274  {
3275  *cutoff = TRUE;
3276  break;
3277  }
3278
3279  if ( SCIPvarIsIntegral(var) )
3280  newbound = SCIPfloor(scip, newbound);
3281
3282  SCIP_CALL( SCIPtightenVarUb(scip, var, newbound, FALSE, &infeasible, &tightened) );
3283  assert( ! infeasible );
3284
3285  if ( tightened )
3286  {
3287  SCIPdebugMsg(scip, "changed upper bound of variable %s from %f to %f \n", SCIPvarGetName(var), ub, newbound);
3288  ++(*nchgbds);
3289  }
3290  }
3291  else if ( SCIPisFeasNegative(scip, linval) && SCIPisFeasLT(scip, lb, newbound) )
3292  {
3293  /* if assumption a_i * x_i != 0 was not correct */
3294  if ( SCIPisFeasLT(scip, ub, newbound) )
3295  {
3296  *cutoff = TRUE;
3297  break;
3298  }
3299
3300  if ( SCIPvarIsIntegral(var) )
3301  newbound = SCIPceil(scip, newbound);
3302
3303  SCIP_CALL( SCIPtightenVarLb(scip, var, newbound, FALSE, &infeasible, &tightened) );
3304  assert( ! infeasible );
3305
3306  if ( tightened )
3307  {
3308  SCIPdebugMsg(scip, "changed lower bound of variable %s from %f to %f \n", SCIPvarGetName(var), lb, newbound);
3309  ++(*nchgbds);
3310  }
3311  }
3312  }
3313
3314  /* update implication graph if possible */
3315  SCIP_CALL( updateImplicationGraphSOS1(scip, conshdlrdata, conflictgraph, adjacencymatrix, implgraph, implhash, implnodes, totalvars, cliquecovers, cliquecoversizes, varincover,
3316  trafolinvars, trafolinvals, ntrafolinvars, trafolbs, var, trafolbv, newboundnonzero, ninftynonzero, FALSE, nchgbds, &update, &infeasible) );
3317  if ( infeasible )
3318  *cutoff = TRUE;
3319  else if ( update )
3320  *implupdate = TRUE;
3321  }
3322
3323  /* free memory */
3324  SCIPfreeBufferArrayNull(scip, &varincover);
3325  for (j = ncliquecovers-1; j >= 0; --j)
3326  SCIPfreeBufferArrayNull(scip, &cliquecovers[j]);
3327  SCIPfreeBufferArrayNull(scip, &cliquecovers);
3328  SCIPfreeBufferArrayNull(scip, &cliquecoversizes);
3329  SCIPfreeBufferArrayNull(scip, &cliquecovervals);
3330  SCIPfreeBufferArrayNull(scip, &trafolinvals);
3331  SCIPfreeBufferArrayNull(scip, &trafolinvars);
3332
3333  if ( *cutoff == TRUE )
3334  break;
3335  } /* end for every linear constraint */
3336
3337  /* free buffer arrays */
3338  SCIPfreeBufferArrayNull(scip, &trafolbs);
3339  SCIPfreeBufferArrayNull(scip, &trafoubs);
3340  SCIPfreeBufferArrayNull(scip, &coveredvars);
3341  SCIPfreeBufferArrayNull(scip, &varindincons);
3342  SCIPfreeBufferArrayNull(scip, &implnodes);
3343  SCIPfreeBufferArrayNull(scip, &sos1linvars);
3344
3345  return SCIP_OKAY;
3346 }
3347
3348
3349 /** perform one presolving round for variables
3350  *
3351  * We perform the following presolving steps:
3352  * - Tighten the bounds of the variables
3353  * - Update conflict graph based on bound implications of the variables
3354  */
3355 static
3357  SCIP* scip, /**< SCIP pointer */
3358  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
3359  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
3361  int nsos1vars, /**< number of SOS1 variables */
3362  int* nfixedvars, /**< pointer to store number of fixed variables */
3363  int* nchgbds, /**< pointer to store number of changed bounds */
3364  int* naddconss, /**< pointer to store number of addded constraints */
3365  SCIP_RESULT* result /**< result */
3366  )
3367 {
3368  SCIP_DIGRAPH* implgraph;
3369  SCIP_HASHMAP* implhash;
3370
3371  SCIP_Bool cutoff = FALSE;
3372  SCIP_Bool updateconfl;
3373
3374  SCIP_VAR** totalvars;
3375  SCIP_VAR** probvars;
3376  int ntotalvars = 0;
3377  int nprobvars;
3378  int i;
3379  int j;
3380
3381  /* determine totalvars (union of SOS1 and problem variables) */
3382  probvars = SCIPgetVars(scip);
3383  nprobvars = SCIPgetNVars(scip);
3384  SCIP_CALL( SCIPhashmapCreate(&implhash, SCIPblkmem(scip), nsos1vars + nprobvars) );
3385  SCIP_CALL( SCIPallocBufferArray(scip, &totalvars, nsos1vars + nprobvars) );
3386
3387  for (i = 0; i < nsos1vars; ++i)
3388  {
3389  SCIP_VAR* var;
3390  var = SCIPnodeGetVarSOS1(conflictgraph, i);
3391
3392  /* insert node number to hash map */
3393  assert( ! SCIPhashmapExists(implhash, var) );
3394  SCIP_CALL( SCIPhashmapInsertInt(implhash, var, ntotalvars) );
3395  assert( ntotalvars == SCIPhashmapGetImageInt(implhash, var) );
3396  totalvars[ntotalvars++] = var;
3397  }
3398
3399  for (i = 0; i < nprobvars; ++i)
3400  {
3401  SCIP_VAR* var;
3402  var = probvars[i];
3403
3404  /* insert node number to hash map if not existent */
3405  if ( ! SCIPhashmapExists(implhash, var) )
3406  {
3407  SCIP_CALL( SCIPhashmapInsertInt(implhash, var, ntotalvars) );
3408  assert( ntotalvars == SCIPhashmapGetImageInt(implhash, var) );
3409  totalvars[ntotalvars++] = var;
3410  }
3411  }
3412
3413  /* create implication graph */
3414  SCIP_CALL( SCIPcreateDigraph(scip, &implgraph, ntotalvars) );
3415
3416  /* try to tighten the lower and upper bounds of the variables */
3417  updateconfl = FALSE;
3418  for (j = 0; (j < conshdlrdata->maxtightenbds || conshdlrdata->maxtightenbds == -1 ) && ! cutoff; ++j)
3419  {
3420  SCIP_Bool implupdate;
3421  int nchgbdssave;
3422
3423  nchgbdssave = *nchgbds;
3424
3425  assert( ntotalvars > 0 );
3426  SCIP_CALL( tightenVarsBoundsSOS1(scip, conshdlrdata, conflictgraph, implgraph, implhash, adjacencymatrix, totalvars, ntotalvars, nsos1vars, nchgbds, &implupdate, &cutoff) );
3427  if ( *nchgbds > nchgbdssave )
3428  {
3429  *result = SCIP_SUCCESS;
3430  if ( implupdate )
3431  updateconfl = TRUE;
3432  }
3433  else if ( implupdate )
3434  updateconfl = TRUE;
3435  else
3436  break;
3437  }
3438
3439  /* perform implication graph analysis */
3440  if ( updateconfl && conshdlrdata->perfimplanalysis && ! cutoff )
3441  {
3442  SCIP_Real* implubs;
3443  SCIP_Real* impllbs;
3444  SCIP_Bool* implnodes;
3445  SCIP_Bool infeasible;
3446  SCIP_Bool fixed;
3448  int probingdepth;
3449
3450  /* allocate buffer arrays */
3451  SCIP_CALL( SCIPallocBufferArray(scip, &implnodes, nsos1vars) );
3452  SCIP_CALL( SCIPallocBufferArray(scip, &impllbs, ntotalvars) );
3453  SCIP_CALL( SCIPallocBufferArray(scip, &implubs, ntotalvars) );
3454
3456  for (i = 0; i < nsos1vars; ++i)
3457  {
3458  /* initialize data for implication graph analysis */
3459  infeasible = FALSE;
3460  probingdepth = 0;
3461  for (j = 0; j < nsos1vars; ++j)
3462  implnodes[j] = FALSE;
3463  for (j = 0; j < ntotalvars; ++j)
3464  {
3465  impllbs[j] = SCIPvarGetLbLocal(totalvars[j]);
3466  implubs[j] = SCIPvarGetUbLocal(totalvars[j]);
3467  }
3468
3469  /* try to update the conflict graph based on the information of the implication graph */
3470  SCIP_CALL( performImplicationGraphAnalysis(scip, conshdlrdata, conflictgraph, totalvars, implgraph, implhash, adjacencymatrix, i, i, impllbs, implubs, implnodes, naddconss, &probingdepth, &infeasible) );
3471
3472  /* if the subproblem turned out to be infeasible then fix variable to zero */
3473  if ( infeasible )
3474  {
3475  SCIP_CALL( SCIPfixVar(scip, totalvars[i], 0.0, &infeasible, &fixed) );
3476
3477  if ( fixed )
3478  {
3479  SCIPdebugMsg(scip, "fixed variable %s with lower bound %f and upper bound %f to zero\n",
3480  SCIPvarGetName(totalvars[i]), SCIPvarGetLbLocal(totalvars[i]), SCIPvarGetUbLocal(totalvars[i]));
3481  ++(*nfixedvars);
3482  }
3483
3484  if ( infeasible )
3485  cutoff = TRUE;
3486  }
3487  }
3488
3490  *result = SCIP_SUCCESS;
3491
3492  /* free buffer arrays */
3493  SCIPfreeBufferArrayNull(scip, &implubs);
3494  SCIPfreeBufferArrayNull(scip, &impllbs);
3495  SCIPfreeBufferArrayNull(scip, &implnodes);
3496  }
3497
3498  /* if an infeasibility has been detected */
3499  if ( cutoff )
3500  {
3501  SCIPdebugMsg(scip, "cutoff \n");
3502  *result = SCIP_CUTOFF;
3503  }
3504
3505  /* free memory */;
3506  for (j = ntotalvars-1; j >= 0; --j)
3507  {
3508  SCIP_SUCCDATA** succdatas;
3509  int nsucc;
3510  int s;
3511
3512  succdatas = (SCIP_SUCCDATA**) SCIPdigraphGetSuccessorsData(implgraph, j);
3513  nsucc = SCIPdigraphGetNSuccessors(implgraph, j);
3514
3515  for (s = nsucc-1; s >= 0; --s)
3516  SCIPfreeBlockMemory(scip, &succdatas[s]);/*lint !e866*/
3517  }
3518  SCIPdigraphFree(&implgraph);
3519  SCIPfreeBufferArrayNull(scip, &totalvars);
3520  SCIPhashmapFree(&implhash);
3521
3522  return SCIP_OKAY;
3523 }
3524
3525
3526 /* ----------------------------- propagation -------------------------------------*/
3527
3528 /** propagate variables of SOS1 constraint */
3529 static
3531  SCIP* scip, /**< SCIP pointer */
3532  SCIP_CONS* cons, /**< constraint */
3533  SCIP_CONSDATA* consdata, /**< constraint data */
3534  SCIP_Bool* cutoff, /**< whether a cutoff happened */
3535  int* ngen /**< number of domain changes */
3536  )
3537 {
3538  assert( scip != NULL );
3539  assert( cons != NULL );
3540  assert( consdata != NULL );
3541  assert( cutoff != NULL );
3542  assert( ngen != NULL );
3543
3544  *cutoff = FALSE;
3545
3546  /* if more than one variable is fixed to be nonzero */
3547  if ( consdata->nfixednonzeros > 1 )
3548  {
3549  SCIPdebugMsg(scip, "the node is infeasible, more than 1 variable is fixed to be nonzero.\n");
3550  SCIP_CALL( SCIPresetConsAge(scip, cons) );
3551  *cutoff = TRUE;
3552  return SCIP_OKAY;
3553  }
3554
3555  /* if exactly one variable is fixed to be nonzero */
3556  if ( consdata->nfixednonzeros == 1 )
3557  {
3558  SCIP_VAR** vars;
3559  SCIP_Bool infeasible;
3560  SCIP_Bool tightened;
3561  SCIP_Bool success;
3562  SCIP_Bool allVarFixed;
3563  int firstFixedNonzero;
3564  int nvars;
3565  int j;
3566
3567  firstFixedNonzero = -1;
3568  nvars = consdata->nvars;
3569  vars = consdata->vars;
3570  assert( vars != NULL );
3571
3572  /* search nonzero variable - is needed for propinfo */
3573  for (j = 0; j < nvars; ++j)
3574  {
3575  if ( SCIPisFeasPositive(scip, SCIPvarGetLbLocal(vars[j])) || SCIPisFeasNegative(scip, SCIPvarGetUbLocal(vars[j])) )
3576  {
3577  firstFixedNonzero = j;
3578  break;
3579  }
3580  }
3581  assert( firstFixedNonzero >= 0 );
3582
3583  SCIPdebugMsg(scip, "variable <%s> is fixed nonzero, fixing other variables to 0.\n", SCIPvarGetName(vars[firstFixedNonzero]));
3584
3585  /* fix variables before firstFixedNonzero to 0 */
3586  allVarFixed = TRUE;
3587  for (j = 0; j < firstFixedNonzero; ++j)
3588  {
3589  /* fix variable */
3590  SCIP_CALL( inferVariableZero(scip, vars[j], cons, firstFixedNonzero, &infeasible, &tightened, &success) );
3591  assert( ! infeasible );
3592  allVarFixed = allVarFixed && success;
3593  if ( tightened )
3594  ++(*ngen);
3595  }
3596
3597  /* fix variables after firstFixedNonzero to 0 */
3598  for (j = firstFixedNonzero+1; j < nvars; ++j)
3599  {
3600  /* fix variable */
3601  SCIP_CALL( inferVariableZero(scip, vars[j], cons, firstFixedNonzero, &infeasible, &tightened, &success) );
3602  assert( ! infeasible ); /* there should be no variables after firstFixedNonzero that are fixed to be nonzero */
3603  allVarFixed = allVarFixed && success;
3604  if ( tightened )
3605  ++(*ngen);
3606  }
3607
3608  /* reset constraint age counter */
3609  if ( *ngen > 0 )
3610  {
3611  SCIP_CALL( SCIPresetConsAge(scip, cons) );
3612  }
3613
3614  /* delete constraint locally */
3615  if ( allVarFixed )
3616  {
3617  assert( !SCIPconsIsModifiable(cons) );
3618  SCIP_CALL( SCIPdelConsLocal(scip, cons) );
3619  }
3620  }
3621
3622  return SCIP_OKAY;
3623 }
3624
3625
3626 /** propagate a variable that is known to be nonzero */
3627 static
3629  SCIP* scip, /**< SCIP pointer */
3630  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
3631  SCIP_DIGRAPH* implgraph, /**< implication graph */
3632  SCIP_CONS* cons, /**< some arbitrary SOS1 constraint */
3633  int node, /**< conflict graph node of variable that is known to be nonzero */
3634  SCIP_Bool implprop, /**< whether implication graph propagation shall be applied */
3635  SCIP_Bool* cutoff, /**< whether a cutoff happened */
3636  int* ngen /**< number of domain changes */
3637  )
3638 {
3639  int inferinfo;
3640  int* succ;
3641  int nsucc;
3642  int s;
3643
3644  assert( scip != NULL );
3645  assert( conflictgraph != NULL );
3646  assert( cutoff != NULL );
3647  assert( ngen != NULL );
3648  assert( node >= 0 );
3649
3650  *cutoff = FALSE;
3651  inferinfo = -node - 1;
3652
3653  /* by assumption zero is outside the domain of variable */
3654  assert( SCIPisFeasPositive(scip, SCIPvarGetLbLocal(SCIPnodeGetVarSOS1(conflictgraph, node))) || SCIPisFeasNegative(scip, SCIPvarGetUbLocal(SCIPnodeGetVarSOS1(conflictgraph, node))) );
3655
3656  /* apply conflict graph propagation (fix all neighbors in the conflict graph to zero) */
3657  succ = SCIPdigraphGetSuccessors(conflictgraph, node);
3658  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, node);
3659  for (s = 0; s < nsucc; ++s)
3660  {
3661  SCIP_VAR* succvar;
3662  SCIP_Real lb;
3663  SCIP_Real ub;
3664
3665  succvar = SCIPnodeGetVarSOS1(conflictgraph, succ[s]);
3666  lb = SCIPvarGetLbLocal(succvar);
3667  ub = SCIPvarGetUbLocal(succvar);
3668
3669  if ( ! SCIPisFeasZero(scip, lb) || ! SCIPisFeasZero(scip, ub) )
3670  {
3671  SCIP_Bool infeasible;
3672  SCIP_Bool tightened;
3673  SCIP_Bool success;
3674
3675  /* fix variable if it is not multi-aggregated */
3676  SCIP_CALL( inferVariableZero(scip, succvar, cons, inferinfo, &infeasible, &tightened, &success) );
3677
3678  if ( infeasible )
3679  {
3680  /* variable cannot be nonzero */
3681  *cutoff = TRUE;
3682  return SCIP_OKAY;
3683  }
3684  if ( tightened )
3685  ++(*ngen);
3686  assert( success || SCIPvarGetStatus(succvar) == SCIP_VARSTATUS_MULTAGGR );
3687  }
3688  }
3689
3690  /* apply implication graph propagation */
3691  if ( implprop && implgraph != NULL )
3692  {
3693  SCIP_SUCCDATA** succdatas;
3694
3695 #ifndef NDEBUG
3696  SCIP_NODEDATA* nodedbgdata;
3697  nodedbgdata = (SCIP_NODEDATA*) SCIPdigraphGetNodeData(implgraph, node);
3698  assert( SCIPvarCompare(nodedbgdata->var, SCIPnodeGetVarSOS1(conflictgraph, node)) == 0 );
3699 #endif
3700
3701  /* get successor datas */
3702  succdatas = (SCIP_SUCCDATA**) SCIPdigraphGetSuccessorsData(implgraph, node);
3703
3704  if ( succdatas != NULL )
3705  {
3706  succ = SCIPdigraphGetSuccessors(implgraph, node);
3707  nsucc = SCIPdigraphGetNSuccessors(implgraph, node);
3708  for (s = 0; s < nsucc; ++s)
3709  {
3710  SCIP_SUCCDATA* succdata;
3711  SCIP_NODEDATA* nodedata;
3712  SCIP_VAR* var;
3713
3714  nodedata = (SCIP_NODEDATA*) SCIPdigraphGetNodeData(implgraph, succ[s]);
3715  assert( nodedata != NULL );
3716  succdata = succdatas[s];
3717  assert( succdata != NULL );
3718  var = nodedata->var;
3719  assert( var != NULL );
3720
3721  /* tighten variable if it is not multi-aggregated */
3723  {
3724  /* check for lower bound implication */
3725  if ( SCIPisFeasLT(scip, SCIPvarGetLbLocal(var), succdata->lbimpl) )
3726  {
3727  SCIP_Bool infeasible;
3728  SCIP_Bool tightened;
3729
3730  SCIP_CALL( SCIPinferVarLbCons(scip, var, succdata->lbimpl, cons, inferinfo, FALSE, &infeasible, &tightened) );
3731  if ( infeasible )
3732  {
3733  *cutoff = TRUE;
3734  return SCIP_OKAY;
3735  }
3736  if ( tightened )
3737  ++(*ngen);
3738  }
3739
3740  /* check for upper bound implication */
3741  if ( SCIPisFeasGT(scip, SCIPvarGetUbLocal(var), succdata->ubimpl) )
3742  {
3743  SCIP_Bool infeasible;
3744  SCIP_Bool tightened;
3745
3746  SCIP_CALL( SCIPinferVarUbCons(scip, var, succdata->ubimpl, cons, inferinfo, FALSE, &infeasible, &tightened) );
3747  if ( infeasible )
3748  {
3749  *cutoff = TRUE;
3750  return SCIP_OKAY;
3751  }
3752  if ( tightened )
3753  ++(*ngen);
3754  }
3755  }
3756  }
3757  }
3758  }
3759
3760  return SCIP_OKAY;
3761 }
3762
3763
3764 /** initialize implication graph
3765  *
3766  * @p j is successor of @p i if and only if \f$x_i\not = 0 \Rightarrow x_j\not = 0\f$
3767  *
3768  * @note By construction the implication graph is globally valid.
3769  */
3770 static
3772  SCIP* scip, /**< SCIP pointer */
3773  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
3774  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
3775  int nsos1vars, /**< number of SOS1 variables */
3776  int maxrounds, /**< maximal number of propagation rounds for generating implications */
3777  int* nchgbds, /**< pointer to store number of bound changes */
3778  SCIP_Bool* cutoff, /**< pointer to store whether a cutoff occurred */
3779  SCIP_Bool* success /**< whether initialization was successful */
3780  )
3781 {
3782  SCIP_HASHMAP* implhash = NULL;
3784  SCIP_Bool* implnodes = NULL;
3785  SCIP_VAR** implvars = NULL;
3786  SCIP_VAR** probvars;
3787  int nimplnodes;
3788  int nprobvars;
3789  int i;
3790  int j;
3791
3792  assert( scip != NULL );
3793  assert( conshdlrdata != NULL );
3794  assert( conflictgraph != NULL );
3795  assert( conshdlrdata->implgraph == NULL );
3796  assert( conshdlrdata->nimplnodes == 0 );
3797  assert( cutoff != NULL );
3798  assert( nchgbds != NULL );
3799
3800  *nchgbds = 0;
3801  *cutoff = FALSE;
3802
3803  /* we do not create the adjacency matrix of the conflict graph if the number of SOS1 variables is larger than a predefined value */
3805  {
3806  *success = FALSE;
3807  SCIPdebugMsg(scip, "Implication graph was not created since number of SOS1 variables (%d) is larger than %d.\n", nsos1vars, conshdlrdata->maxsosadjacency);
3808
3809  return SCIP_OKAY;
3810  }
3811  *success = TRUE;
3812
3813  /* only add globally valid implications to implication graph */
3814  assert ( SCIPgetDepth(scip) == 0 );
3815
3816  probvars = SCIPgetVars(scip);
3817  nprobvars = SCIPgetNVars(scip);
3818  nimplnodes = 0;
3819
3820  /* create implication graph */
3821  SCIP_CALL( SCIPcreateDigraph(scip, &conshdlrdata->implgraph, nsos1vars + nprobvars) );
3822
3823  /* create hashmap */
3824  SCIP_CALL( SCIPhashmapCreate(&implhash, SCIPblkmem(scip), nsos1vars + nprobvars) );
3825
3826  /* determine implvars (union of SOS1 and problem variables)
3827  * Note: For separation of implied bound cuts it is important that SOS1 variables are enumerated first
3828  */
3829  SCIP_CALL( SCIPallocBufferArray(scip, &implvars, nsos1vars + nprobvars) );
3830  for (i = 0; i < nsos1vars; ++i)
3831  {
3832  SCIP_VAR* var;
3833  var = SCIPnodeGetVarSOS1(conflictgraph, i);
3834
3835  /* insert node number to hash map */
3836  assert( ! SCIPhashmapExists(implhash, var) );
3837  SCIP_CALL( SCIPhashmapInsertInt(implhash, var, nimplnodes) );
3838  assert( nimplnodes == SCIPhashmapGetImageInt(implhash, var) );
3839  implvars[nimplnodes++] = var;
3840  }
3841
3842  for (i = 0; i < nprobvars; ++i)
3843  {
3844  SCIP_VAR* var;
3845  var = probvars[i];
3846
3847  /* insert node number to hash map if not existent */
3848  if ( ! SCIPhashmapExists(implhash, var) )
3849  {
3850  SCIP_CALL( SCIPhashmapInsertInt(implhash, var, nimplnodes) );
3851  assert( nimplnodes == SCIPhashmapGetImageInt(implhash, var) );
3852  implvars[nimplnodes++] = var;
3853  }
3854  }
3855  conshdlrdata->nimplnodes = nimplnodes;
3856
3857  /* add variables to nodes of implication graph */
3858  for (i = 0; i < nimplnodes; ++i)
3859  {
3860  SCIP_NODEDATA* nodedata = NULL;
3861
3862  /* create node data */
3863  SCIP_CALL( SCIPallocBlockMemory(scip, &nodedata) );
3864  nodedata->var = implvars[i];
3865
3866  /* set node data */
3867  SCIPdigraphSetNodeData(conshdlrdata->implgraph, (void*) nodedata, i);
3868  }
3869
3870  /* allocate buffer arrays */
3871  SCIP_CALL( SCIPallocBufferArray(scip, &implnodes, nsos1vars) );
3872  SCIP_CALL( SCIPallocBufferArray(scip, &adjacencymatrix, nsos1vars) );
3873
3874  for (i = 0; i < nsos1vars; ++i)
3875  SCIP_CALL( SCIPallocBufferArray(scip, &adjacencymatrix[i], i+1) ); /*lint !e866*/
3876
3877  /* create adjacency matrix */
3878  for (i = 0; i < nsos1vars; ++i)
3879  {
3880  for (j = 0; j < i+1; ++j)
3882  }
3883
3884  for (i = 0; i < nsos1vars; ++i)
3885  {
3886  int* succ;
3887  int nsucc;
3888  succ = SCIPdigraphGetSuccessors(conflictgraph, i);
3889  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, i);
3890
3891  for (j = 0; j < nsucc; ++j)
3892  {
3893  if ( i > succ[j] )
3895  }
3896  }
3897
3898  assert( SCIPgetDepth(scip) == 0 );
3899
3900  /* compute SOS1 implications from linear constraints and tighten bounds of variables */
3901  for (j = 0; (j < maxrounds || maxrounds == -1 ); ++j)
3902  {
3903  SCIP_Bool implupdate;
3904  int nchgbdssave;
3905
3906  nchgbdssave = *nchgbds;
3907
3908  assert( nimplnodes > 0 );
3909  SCIP_CALL( tightenVarsBoundsSOS1(scip, conshdlrdata, conflictgraph, conshdlrdata->implgraph, implhash, adjacencymatrix, implvars, nimplnodes, nsos1vars, nchgbds, &implupdate, cutoff) );
3910  if ( *cutoff || ( ! implupdate && ! ( *nchgbds > nchgbdssave ) ) )
3911  break;
3912  }
3913
3914  /* free memory */
3915  for (i = nsos1vars-1; i >= 0; --i)
3918  SCIPfreeBufferArrayNull(scip, &implnodes);
3919  SCIPfreeBufferArrayNull(scip, &implvars);
3920  SCIPhashmapFree(&implhash);
3921
3922 #ifdef SCIP_DEBUG
3923  /* evaluate results */
3924  if ( cutoff )
3925  {
3926  SCIPdebugMsg(scip, "cutoff \n");
3927  }
3928  else if ( *nchgbds > 0 )
3929  {
3930  SCIPdebugMsg(scip, "found %d bound changes\n", *nchgbds);
3931  }
3932 #endif
3933
3934  assert( conshdlrdata->implgraph != NULL );
3935
3936  return SCIP_OKAY;
3937 }
3938
3939
3940 /** deinitialize implication graph */
3941 static
3943  SCIP* scip, /**< SCIP pointer */
3944  SCIP_CONSHDLRDATA* conshdlrdata /**< constraint handler data */
3945  )
3946 {
3947  int j;
3949  assert( scip != NULL );
3950  assert( conshdlrdata != NULL );
3951
3952  /* free whole memory of implication graph */
3953  if ( conshdlrdata->implgraph == NULL )
3954  {
3955  assert( conshdlrdata->nimplnodes == 0 );
3956  return SCIP_OKAY;
3957  }
3958
3959  /* free arc data */
3960  for (j = conshdlrdata->nimplnodes-1; j >= 0; --j)
3961  {
3962  SCIP_SUCCDATA** succdatas;
3963  int nsucc;
3964  int s;
3965
3966  succdatas = (SCIP_SUCCDATA**) SCIPdigraphGetSuccessorsData(conshdlrdata->implgraph, j);
3967  nsucc = SCIPdigraphGetNSuccessors(conshdlrdata->implgraph, j);
3968
3969  for (s = nsucc-1; s >= 0; --s)
3970  {
3971  assert( succdatas[s] != NULL );
3972  SCIPfreeBlockMemory(scip, &succdatas[s]);/*lint !e866*/
3973  }
3974  }
3975
3976  /* free node data */
3977  for (j = conshdlrdata->nimplnodes-1; j >= 0; --j)
3978  {
3979  SCIP_NODEDATA* nodedata;
3980  nodedata = (SCIP_NODEDATA*)SCIPdigraphGetNodeData(conshdlrdata->implgraph, j);
3981  assert( nodedata != NULL );
3982  SCIPfreeBlockMemory(scip, &nodedata);
3983  SCIPdigraphSetNodeData(conshdlrdata->implgraph, NULL, j);
3984  }
3985
3986  /* free implication graph */
3987  SCIPdigraphFree(&conshdlrdata->implgraph);
3988  conshdlrdata->nimplnodes = 0;
3989
3990  return SCIP_OKAY;
3991 }
3992
3993
3994 /* ----------------------------- branching -------------------------------------*/
3995
3996 /** get the vertices whose neighbor set covers a subset of the neighbor set of a given other vertex.
3997  *
3998  * This function can be used to compute sets of variables to branch on.
3999  */
4000 static
4002  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
4003  SCIP_Bool* verticesarefixed, /**< array that indicates which variables are currently fixed to zero */
4004  int vertex, /**< vertex (-1 if not needed) */
4005  int* neightocover, /**< neighbors of given vertex to be covered (or NULL if all neighbors shall be covered) */
4006  int nneightocover, /**< number of entries of neightocover (or 0 if all neighbors shall be covered )*/
4007  int* coververtices, /**< array to store the vertices whose neighbor set covers the neighbor set of the given vertex */
4008  int* ncoververtices /**< pointer to store size of coververtices */
4009  )
4010 {
4011  int* succ1;
4012  int nsucc1;
4013  int s;
4014
4015  assert( conflictgraph != NULL );
4016  assert( verticesarefixed != NULL );
4017  assert( coververtices != NULL );
4018  assert( ncoververtices != NULL );
4019
4020  *ncoververtices = 0;
4021
4022  /* if all the neighbors shall be covered */
4023  if ( neightocover == NULL )
4024  {
4025  assert( nneightocover == 0 );
4026  nsucc1 = SCIPdigraphGetNSuccessors(conflictgraph, vertex);
4027  succ1 = SCIPdigraphGetSuccessors(conflictgraph, vertex);
4028  }
4029  else
4030  {
4031  nsucc1 = nneightocover;
4032  succ1 = neightocover;
4033  }
4034
4035  /* determine all the successors of the first unfixed successor */
4036  for (s = 0; s < nsucc1; ++s)
4037  {
4038  int succvertex1 = succ1[s];
4039
4040  if ( ! verticesarefixed[succvertex1] )
4041  {
4042  int succvertex2;
4043  int* succ2;
4044  int nsucc2;
4045  int j;
4046
4047  nsucc2 = SCIPdigraphGetNSuccessors(conflictgraph, succvertex1);
4048  succ2 = SCIPdigraphGetSuccessors(conflictgraph, succvertex1);
4049
4050  /* for the first unfixed vertex */
4051  if ( *ncoververtices == 0 )
4052  {
4053  for (j = 0; j < nsucc2; ++j)
4054  {
4055  succvertex2 = succ2[j];
4056  if ( ! verticesarefixed[succvertex2] )
4057  coververtices[(*ncoververtices)++] = succvertex2;
4058  }
4059  }
4060  else
4061  {
4062  int vv = 0;
4063  int k = 0;
4064  int v;
4065
4066  /* determine all the successors that are in the set "coververtices" */
4067  for (v = 0; v < *ncoververtices; ++v)
4068  {
4069  assert( vv <= v );
4070  for (j = k; j < nsucc2; ++j)
4071  {
4072  succvertex2 = succ2[j];
4073  if ( succvertex2 > coververtices[v] )
4074  {
4075  /* coververtices[v] does not appear in succ2 list, go to next vertex in coververtices */
4076  k = j;
4077  break;
4078  }
4079  else if ( succvertex2 == coververtices[v] )
4080  {
4081  /* vertices are equal, copy to free position vv */
4082  coververtices[vv++] = succvertex2;
4083  k = j + 1;
4084  break;
4085  }
4086  }
4087  }
4088  /* store new size of coververtices */
4089  *ncoververtices = vv;
4090  }
4091  }
4092  }
4093
4094 #ifdef SCIP_DEBUG
4095  /* check sorting */
4096  for (s = 0; s < *ncoververtices; ++s)
4097  {
4098  assert( *ncoververtices <= 1 || coververtices[*ncoververtices - 1] > coververtices[*ncoververtices - 2] );
4099  }
4100 #endif
4101
4102  return SCIP_OKAY;
4103 }
4104
4105
4106 /** get vertices of variables that will be fixed to zero for each node */
4107 static
4109  SCIP* scip, /**< SCIP pointer */
4110  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
4111  SCIP_SOL* sol, /**< solution to be enforced (NULL for LP solution) */
4112  SCIP_Bool* verticesarefixed, /**< vector that indicates which variables are currently fixed to zero */
4113  SCIP_Bool bipbranch, /**< TRUE if bipartite branching method should be used */
4114  int branchvertex, /**< branching vertex */
4115  int* fixingsnode1, /**< vertices of variables that will be fixed to zero for the first node */
4116  int* nfixingsnode1, /**< pointer to store number of fixed variables for the first node */
4117  int* fixingsnode2, /**< vertices of variables that will be fixed to zero for the second node */
4118  int* nfixingsnode2 /**< pointer to store number of fixed variables for the second node */
4119  )
4120 {
4121  SCIP_Bool takeallsucc; /* whether to set fixingsnode1 = neighbors of 'branchvertex' in the conflict graph */
4122  int* succ;
4123  int nsucc;
4124  int j;
4125
4126  assert( scip != NULL );
4127  assert( conflictgraph != NULL );
4128  assert( verticesarefixed != NULL );
4129  assert( ! verticesarefixed[branchvertex] );
4130  assert( fixingsnode1 != NULL );
4131  assert( fixingsnode2 != NULL );
4132  assert( nfixingsnode1 != NULL );
4133  assert( nfixingsnode2 != NULL );
4134
4135  *nfixingsnode1 = 0;
4136  *nfixingsnode2 = 0;
4137  takeallsucc = TRUE;
4138
4139  /* get successors and number of successors of branching vertex */
4140  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, branchvertex);
4141  succ = SCIPdigraphGetSuccessors(conflictgraph, branchvertex);
4142
4143  /* if bipartite branching method is turned on */
4144  if ( bipbranch )
4145  {
4146  SCIP_Real solval;
4147  int cnt = 0;
4148
4149  /* get all the neighbors of the variable with index 'branchvertex' whose solution value is nonzero */
4150  for (j = 0; j < nsucc; ++j)
4151  {
4152  if ( ! SCIPisFeasZero(scip, SCIPgetSolVal(scip, sol, SCIPnodeGetVarSOS1(conflictgraph, succ[j]))) )
4153  {
4154  assert( ! verticesarefixed[succ[j]] );
4155  fixingsnode1[(*nfixingsnode1)++] = succ[j];
4156  }
4157  }
4158
4159  /* if one of the sets fixingsnode1 or fixingsnode2 contains only one variable with a nonzero LP value we perform standard neighborhood branching */
4160  if ( *nfixingsnode1 > 0 )
4161  {
4162  /* get the vertices whose neighbor set cover the selected subset of the neighbors of the given branching vertex */
4163  SCIP_CALL( getCoverVertices(conflictgraph, verticesarefixed, branchvertex, fixingsnode1, *nfixingsnode1, fixingsnode2, nfixingsnode2) );
4164
4165  /* determine the intersection of the neighbors of branchvertex with the intersection of all the neighbors of fixingsnode2 */
4166  SCIP_CALL( getCoverVertices(conflictgraph, verticesarefixed, branchvertex, fixingsnode2, *nfixingsnode2, fixingsnode1, nfixingsnode1) );
4167
4168  for (j = 0; j < *nfixingsnode2; ++j)
4169  {
4170  solval = SCIPgetSolVal(scip, sol, SCIPnodeGetVarSOS1(conflictgraph, fixingsnode2[j]));
4171  if( ! SCIPisFeasZero(scip, solval) )
4172  ++cnt;
4173  }
4174
4175  /* we decide whether to use all successors if one partition of complete bipartite subgraph has only one node */
4176  if ( cnt >= 2 )
4177  {
4178  cnt = 0;
4179  for (j = 0; j < *nfixingsnode1; ++j)
4180  {
4181  solval = SCIPgetSolVal(scip, sol, SCIPnodeGetVarSOS1(conflictgraph, fixingsnode1[j]));
4182  if( ! SCIPisFeasZero(scip, solval) )
4183  ++cnt;
4184  }
4185
4186  if ( cnt >= 2 )
4187  takeallsucc = FALSE;
4188  }
4189  }
4190  }
4191
4192  if ( takeallsucc )
4193  {
4194  /* get all the unfixed neighbors of the branching vertex */
4195  *nfixingsnode1 = 0;
4196  for (j = 0; j < nsucc; ++j)
4197  {
4198  if ( ! verticesarefixed[succ[j]] )
4199  fixingsnode1[(*nfixingsnode1)++] = succ[j];
4200  }
4201
4202  if ( bipbranch )
4203  {
4204  /* get the vertices whose neighbor set covers the neighbor set of a given branching vertex */
4205  SCIP_CALL( getCoverVertices(conflictgraph, verticesarefixed, branchvertex, fixingsnode1, *nfixingsnode1, fixingsnode2, nfixingsnode2) );
4206  }
4207  else
4208  {
4209  /* use neighborhood branching, i.e, for the second node only the branching vertex can be fixed */
4210  fixingsnode2[0] = branchvertex;
4211  *nfixingsnode2 = 1;
4212  }
4213  }
4214
4215  return SCIP_OKAY;
4216 }
4217
4218
4219 /** gets branching priorities for SOS1 variables and applies 'most infeasible selection' rule to determine a vertex for the next branching decision */
4220 static
4222  SCIP* scip, /**< SCIP pointer */
4223  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
4224  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
4225  SCIP_SOL* sol, /**< solution to be enforced (NULL for LP solution) */
4226  int nsos1vars, /**< number of SOS1 variables */
4227  SCIP_Bool* verticesarefixed, /**< vector that indicates which variables are currently fixed to zero */
4228  SCIP_Bool bipbranch, /**< TRUE if bipartite branching method should be used */
4229  int* fixingsnode1, /**< vertices of variables that will be fixed to zero for the first node (size = nsos1vars) */
4230  int* fixingsnode2, /**< vertices of variables that will be fixed to zero for the second node (size = nsos1vars) */
4231  SCIP_Real* branchpriors, /**< pointer to store branching priorities (size = nsos1vars) or NULL if not needed */
4232  int* vertexbestprior, /**< pointer to store vertex with the best branching priority or NULL if not needed */
4233  SCIP_Bool* relsolfeas /**< pointer to store if LP relaxation solution is feasible */
4234  )
4235 {
4236  SCIP_Real bestprior;
4237  int i;
4238
4239  assert( scip != NULL );
4240  assert( conshdlrdata != NULL );
4241  assert( conflictgraph != NULL );
4242  assert( verticesarefixed != NULL );
4243  assert( fixingsnode1 != NULL );
4244  assert( fixingsnode2 != NULL );
4245  assert( relsolfeas != NULL );
4246
4247  bestprior = -SCIPinfinity(scip);
4248
4249  /* make sure data is initialized */
4250  if ( vertexbestprior != NULL )
4251  *vertexbestprior = -1;
4252
4253  for (i = 0; i < nsos1vars; ++i)
4254  {
4255  SCIP_Real prior;
4256  SCIP_Real solval;
4257  int nfixingsnode1;
4258  int nfixingsnode2;
4259  int nsucc;
4260  int j;
4261
4262  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, i);
4263
4264  if ( nsucc == 0 || SCIPisFeasZero(scip, SCIPgetSolVal(scip, sol, SCIPnodeGetVarSOS1(conflictgraph, i))) || verticesarefixed[i] )
4265  prior = -SCIPinfinity(scip);
4266  else
4267  {
4268  SCIP_Bool iszero1 = TRUE;
4269  SCIP_Bool iszero2 = TRUE;
4270  SCIP_Real sum1 = 0.0;
4271  SCIP_Real sum2 = 0.0;
4272
4273  /* get vertices of variables that will be fixed to zero for each strong branching execution */
4274  assert( ! verticesarefixed[i] );
4275  SCIP_CALL( getBranchingVerticesSOS1(scip, conflictgraph, sol, verticesarefixed, bipbranch, i, fixingsnode1, &nfixingsnode1, fixingsnode2, &nfixingsnode2) );
4276
4277  for (j = 0; j < nfixingsnode1; ++j)
4278  {
4279  solval = SCIPgetSolVal(scip, sol, SCIPnodeGetVarSOS1(conflictgraph, fixingsnode1[j]));
4280  if ( ! SCIPisFeasZero(scip, solval) )
4281  {
4282  sum1 += REALABS( solval );
4283  iszero1 = FALSE;
4284  }
4285  }
4286
4287  for (j = 0; j < nfixingsnode2; ++j)
4288  {
4289  solval = SCIPgetSolVal(scip, sol, SCIPnodeGetVarSOS1(conflictgraph, fixingsnode2[j]));
4290  if ( ! SCIPisFeasZero(scip, solval) )
4291  {
4292  sum2 += REALABS( solval );
4293  iszero2 = FALSE;
4294  }
4295  }
4296
4297  if ( iszero1 || iszero2 )
4298  prior = -SCIPinfinity(scip);
4299  else
4300  prior = sum1 * sum2;
4301  }
4302
4303  if ( branchpriors != NULL )
4304  branchpriors[i] = prior;
4305  if ( bestprior < prior )
4306  {
4307  bestprior = prior;
4308
4309  if ( vertexbestprior != NULL )
4310  *vertexbestprior = i;
4311  }
4312  }
4313
4314  if ( SCIPisInfinity(scip, -bestprior) )
4315  *relsolfeas = TRUE;
4316  else
4317  *relsolfeas = FALSE;
4318
4319  return SCIP_OKAY;
4320 }
4321
4322
4323 /** performs strong branching with given domain fixings */
4324 static
4326  SCIP* scip, /**< SCIP pointer */
4327  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
4328  int* fixingsexec, /**< vertices of variables to be fixed to zero for this strong branching execution */
4329  int nfixingsexec, /**< number of vertices of variables to be fixed to zero for this strong branching execution */
4330  int* fixingsop, /**< vertices of variables to be fixed to zero for the opposite strong branching execution */
4331  int nfixingsop, /**< number of vertices of variables to be fixed to zero for the opposite strong branching execution */
4332  int inititer, /**< maximal number of LP iterations to perform */
4333  SCIP_Bool fixnonzero, /**< shall opposite variable (if positive in sign) fixed to the feasibility tolerance
4334  * (only possible if nfixingsop = 1) */
4335  int* domainfixings, /**< vertices that can be used to reduce the domain (should have size equal to number of variables) */
4336  int* ndomainfixings, /**< pointer to store number of vertices that can be used to reduce the domain, could be filled by earlier calls */
4337  SCIP_Bool* infeasible, /**< pointer to store whether branch is infeasible */
4338  SCIP_Real* objval, /**< pointer to store objective value of LP with fixed variables (SCIP_INVALID if reddomain = TRUE or lperror = TRUE) */
4339  SCIP_Bool* lperror /**< pointer to store whether an unresolved LP error or a strange solution status occurred */
4340  )
4341 {
4342  SCIP_LPSOLSTAT solstat;
4343  int i;
4344
4345  assert( scip != NULL );
4346  assert( conflictgraph != NULL );
4347  assert( fixingsexec != NULL );
4348  assert( nfixingsop > 0 );
4349  assert( fixingsop != NULL );
4350  assert( nfixingsop > 0 );
4351  assert( inititer >= -1 );
4352  assert( domainfixings != NULL );
4353  assert( ndomainfixings != NULL );
4354  assert( *ndomainfixings >= 0 );
4355  assert( infeasible != NULL );
4356  assert( objval != NULL );
4357  assert( lperror != NULL );
4358
4359  *objval = SCIP_INVALID; /* for debugging */
4360  *lperror = FALSE;
4361  *infeasible = FALSE;
4362
4363  /* start probing */
4364  SCIP_CALL( SCIPstartProbing(scip) );
4365
4366  /* perform domain fixings */
4367  if ( fixnonzero && nfixingsop == 1 )
4368  {
4369  SCIP_VAR* var;
4370  SCIP_Real lb;
4371  SCIP_Real ub;
4372
4373  var = SCIPnodeGetVarSOS1(conflictgraph, fixingsop[0]);
4374  lb = SCIPvarGetLbLocal(var);
4375  ub = SCIPvarGetUbLocal(var);
4376
4378  {
4379  if ( SCIPisZero(scip, lb) )
4380  {
4381  /* fix variable to some very small, but positive number or to 1.0 if variable is integral */
4382  if (SCIPvarIsIntegral(var) )
4383  {
4384  SCIP_CALL( SCIPchgVarLbProbing(scip, var, 1.0) );
4385  }
4386  else
4387  {
4388  SCIP_CALL( SCIPchgVarLbProbing(scip, var, 1.5 * SCIPfeastol(scip)) );
4389  }
4390  }
4391  else if ( SCIPisZero(scip, ub) )
4392  {
4393  /* fix variable to some negative number with small absolute value or to -1.0 if variable is integral */
4394  if (SCIPvarIsIntegral(var) )
4395  {
4396  SCIP_CALL( SCIPchgVarUbProbing(scip, var, -1.0) );
4397  }
4398  else
4399  {
4400  SCIP_CALL( SCIPchgVarUbProbing(scip, var, -1.5 * SCIPfeastol(scip)) );
4401  }
4402  }
4403  }
4404  }
4405
4406  /* injects variable fixings into current probing node */
4407  for (i = 0; i < nfixingsexec && ! *infeasible; ++i)
4408  {
4409  SCIP_VAR* var;
4410
4411  var = SCIPnodeGetVarSOS1(conflictgraph, fixingsexec[i]);
4412  if ( SCIPisFeasGT(scip, SCIPvarGetLbLocal(var), 0.0) || SCIPisFeasLT(scip, SCIPvarGetUbLocal(var), 0.0) )
4413  *infeasible = TRUE;
4414  else
4415  {
4416  SCIP_CALL( SCIPfixVarProbing(scip, var, 0.0) );
4417  }
4418  }
4419
4420  /* apply domain propagation */
4421  if ( ! *infeasible )
4422  {
4423  SCIP_CALL( SCIPpropagateProbing(scip, 0, infeasible, NULL) );
4424  }
4425
4426  if ( *infeasible )
4427  solstat = SCIP_LPSOLSTAT_INFEASIBLE;
4428  else
4429  {
4430  /* solve the probing LP */
4431  SCIP_CALL( SCIPsolveProbingLP(scip, inititer, lperror, NULL) );
4432  if ( *lperror )
4433  {
4434  SCIP_CALL( SCIPendProbing(scip) );
4435  return SCIP_OKAY;
4436  }
4437
4438  /* get solution status */
4439  solstat = SCIPgetLPSolstat(scip);
4440  }
4441
4442  /* if objective limit was reached, then the domain can be reduced */
4443  if ( solstat == SCIP_LPSOLSTAT_OBJLIMIT || solstat == SCIP_LPSOLSTAT_INFEASIBLE )
4444  {
4445  *infeasible = TRUE;
4446
4447  for (i = 0; i < nfixingsop; ++i)
4448  domainfixings[(*ndomainfixings)++] = fixingsop[i];
4449  }
4450  else if ( solstat == SCIP_LPSOLSTAT_OPTIMAL || solstat == SCIP_LPSOLSTAT_TIMELIMIT || solstat == SCIP_LPSOLSTAT_ITERLIMIT )
4451  {
4452  /* get objective value of probing LP */
4453  *objval = SCIPgetLPObjval(scip);
4454  }
4455  else
4456  *lperror = TRUE;
4457
4458  /* end probing */
4459  SCIP_CALL( SCIPendProbing(scip) );
4460
4461  return SCIP_OKAY;
4462 }
4463
4464
4465 /** apply strong branching to determine the vertex for the next branching decision */
4466 static
4468  SCIP* scip, /**< SCIP pointer */
4469  SCIP_CONSHDLRDATA* conshdlrdata, /**< SOS1 constraint handler data */
4470  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
4471  SCIP_SOL* sol, /**< solution to be enforced (NULL for LP solution) */
4472  int nsos1vars, /**< number of SOS1 variables */
4473  SCIP_Real lpobjval, /**< current LP relaxation solution */
4474  SCIP_Bool bipbranch, /**< TRUE if bipartite branching method should be used */
4475  int nstrongrounds, /**< number of strong branching rounds */
4476  SCIP_Bool* verticesarefixed, /**< vector that indicates which variables are currently fixed to zero */
4477  int* fixingsnode1, /**< pointer to store vertices of variables that will be fixed to zero for the first node (size = nsos1vars) */
4478  int* fixingsnode2, /**< pointer to store vertices of variables that will be fixed to zero for the second node (size = nsos1vars) */
4479  int* vertexbestprior, /**< pointer to store vertex with the best strong branching priority */
4480  SCIP_Real* bestobjval1, /**< pointer to store LP objective for left child node of branching decision with best priority */
4481  SCIP_Real* bestobjval2, /**< pointer to store LP objective for right child node of branching decision with best priority */
4482  SCIP_RESULT* result /**< pointer to store result of strong branching */
4483  )
4484 {
4485  SCIP_Real* branchpriors = NULL;
4486  int* indsos1vars = NULL;
4487  int* domainfixings = NULL;
4488  int ndomainfixings;
4489  int nfixingsnode1;
4490  int nfixingsnode2;
4491
4492  SCIP_Bool relsolfeas;
4493  SCIP_Real bestscore;
4494  int lastscorechange;
4495  int maxfailures;
4496
4497  SCIP_Longint nlpiterations;
4498  SCIP_Longint nlps;
4499  int inititer;
4500  int j;
4501  int i;
4502
4503  assert( scip != NULL );
4504  assert( conshdlrdata != NULL );
4505  assert( conflictgraph != NULL );
4506  assert( verticesarefixed != NULL );
4507  assert( fixingsnode1 != NULL );
4508  assert( fixingsnode2 != NULL );
4509  assert( vertexbestprior != NULL );
4510  assert( result != NULL );
4511
4512  /* allocate buffer arrays */
4513  SCIP_CALL( SCIPallocBufferArray(scip, &branchpriors, nsos1vars) );
4514
4515  /* get branching priorities */
4516  SCIP_CALL( getBranchingPrioritiesSOS1(scip, conshdlrdata, conflictgraph, sol, nsos1vars, verticesarefixed,
4517  bipbranch, fixingsnode1, fixingsnode2, branchpriors, NULL, &relsolfeas) );
4518
4519  /* if LP relaxation solution is feasible */
4520  if ( relsolfeas )
4521  {
4522  SCIPdebugMsg(scip, "all the SOS1 constraints are feasible.\n");
4523  *vertexbestprior = -1;
4524  *result = SCIP_FEASIBLE;
4525
4526  /* free memory */
4527  SCIPfreeBufferArrayNull(scip, &branchpriors);
4528
4529  return SCIP_OKAY;
4530  }
4531
4532  /* allocate buffer arrays */
4533  SCIP_CALL( SCIPallocBufferArray(scip, &indsos1vars, nsos1vars) );
4534  SCIP_CALL( SCIPallocBufferArray(scip, &domainfixings, nsos1vars) );
4535
4536  /* sort branching priorities (descending order) */
4537  for (j = 0; j < nsos1vars; ++j)
4538  indsos1vars[j] = j;
4539  SCIPsortDownRealInt(branchpriors, indsos1vars, nsos1vars);
4540
4541  /* determine the number of LP iterations to perform in each strong branch */
4542  nlpiterations = SCIPgetNDualResolveLPIterations(scip);
4543  nlps = SCIPgetNDualResolveLPs(scip);
4544  if ( nlps == 0 )
4545  {
4546  nlpiterations = SCIPgetNNodeInitLPIterations(scip);
4547  nlps = SCIPgetNNodeInitLPs(scip);
4548  if ( nlps == 0 )
4549  {
4550  nlpiterations = 1000;
4551  nlps = 1;
4552  }
4553  }
4554  assert(nlps >= 1);
4555
4556  /* compute number of LP iterations performed per strong branching iteration */
4557  if ( conshdlrdata->nstrongiter == -2 )
4558  {
4559  inititer = (int)(2*nlpiterations / nlps);
4560  inititer = (int)((SCIP_Real)inititer * (1.0 + 20.0/SCIPgetNNodes(scip)));
4561  inititer = MAX(inititer, 10);
4562  inititer = MIN(inititer, 500);
4563  }
4564  else
4565  inititer = conshdlrdata->nstrongiter;
4566
4567  /* get current LP relaxation solution */
4568  lpobjval = SCIPgetLPObjval(scip);
4569
4570  /* determine branching variable by strong branching or reduce domain */
4571  ndomainfixings = 0;
4572  lastscorechange = -1;
4573  assert( nsos1vars > 0 );
4574  *vertexbestprior = indsos1vars[0]; /* for the case that nstrongrounds = 0 */
4575  bestscore = -SCIPinfinity(scip);
4576  *bestobjval1 = -SCIPinfinity(scip);
4577  *bestobjval2 = -SCIPinfinity(scip);
4578  maxfailures = nstrongrounds;
4579
4580  /* for each strong branching round */
4581  for (j = 0; j < nstrongrounds; ++j)
4582  {
4583  int testvertex;
4584
4585  /* get branching vertex for the current strong branching iteration */
4586  testvertex = indsos1vars[j];
4587
4588  /* if variable with index 'vertex' does not violate any complementarity in its neighborhood for the current LP relaxation solution */
4589  if ( SCIPisPositive(scip, branchpriors[j]) )
4590  {
4591  SCIP_Bool infeasible1;
4592  SCIP_Bool infeasible2;
4593  SCIP_Bool lperror;
4594  SCIP_Real objval1;
4595  SCIP_Real objval2;
4596  SCIP_Real score;
4597
4598  /* get vertices of variables that will be fixed to zero for each strong branching execution */
4599  assert( ! verticesarefixed[testvertex] );
4600  SCIP_CALL( getBranchingVerticesSOS1(scip, conflictgraph, sol, verticesarefixed, bipbranch, testvertex,
4601  fixingsnode1, &nfixingsnode1, fixingsnode2, &nfixingsnode2) );
4602
4603  /* get information for first strong branching execution */
4604  SCIP_CALL( performStrongbranchSOS1(scip, conflictgraph, fixingsnode1, nfixingsnode1, fixingsnode2, nfixingsnode2,
4605  inititer, conshdlrdata->fixnonzero, domainfixings, &ndomainfixings, &infeasible1, &objval1, &lperror) );
4606  if ( lperror )
4607  continue;
4608
4609  /* get information for second strong branching execution */
4610  SCIP_CALL( performStrongbranchSOS1(scip, conflictgraph, fixingsnode2, nfixingsnode2, fixingsnode1, nfixingsnode1,
4611  inititer, FALSE, domainfixings, &ndomainfixings, &infeasible2, &objval2, &lperror) );
4612  if ( lperror )
4613  continue;
4614
4615  /* if both subproblems are infeasible */
4616  if ( infeasible1 && infeasible2 )
4617  {
4618  SCIPdebugMsg(scip, "detected cutoff.\n");
4619
4620  /* update result */
4621  *result = SCIP_CUTOFF;
4622
4623  /* free memory */
4624  SCIPfreeBufferArrayNull(scip, &domainfixings);
4625  SCIPfreeBufferArrayNull(scip, &indsos1vars);
4626  SCIPfreeBufferArrayNull(scip, &branchpriors);
4627
4628  return SCIP_OKAY;
4629  }
4630  else if ( ! infeasible1 && ! infeasible2 ) /* both subproblems are feasible */
4631  {
4632  /* if domain has not been reduced in this for-loop */
4633  if ( ndomainfixings == 0 )
4634  {
4635  score = MAX( REALABS(objval1 - lpobjval), SCIPfeastol(scip) ) * MAX( REALABS(objval2 - lpobjval), SCIPfeastol(scip) );/*lint !e666*/
4636
4637  if ( SCIPisPositive(scip, score - bestscore) )
4638  {
4639  bestscore = score;
4640  *vertexbestprior = testvertex;
4641  *bestobjval1 = objval1;
4642  *bestobjval2 = objval2;
4643
4644  lastscorechange = j;
4645  }
4646  else if ( j - lastscorechange > maxfailures )
4647  break;
4648  }
4649  }
4650  }
4651  }
4652
4653  /* if variable fixings have been detected by probing, then reduce domain */
4654  if ( ndomainfixings > 0 )
4655  {
4656  SCIP_NODE* node = SCIPgetCurrentNode(scip);
4657  SCIP_Bool infeasible;
4658
4659  for (i = 0; i < ndomainfixings; ++i)
4660  {
4661  SCIP_CALL( fixVariableZeroNode(scip, SCIPnodeGetVarSOS1(conflictgraph, domainfixings[i]), node, &infeasible) );
4662  assert( ! infeasible );
4663  }
4664
4665  SCIPdebugMsg(scip, "found %d domain fixings.\n", ndomainfixings);
4666
4667  /* update result */
4668  *result = SCIP_REDUCEDDOM;
4669  }
4670
4671  /* free buffer arrays */
4672  SCIPfreeBufferArrayNull(scip, &domainfixings);
4673  SCIPfreeBufferArrayNull(scip, &indsos1vars);
4674  SCIPfreeBufferArrayNull(scip, &branchpriors);
4675
4676  return SCIP_OKAY;
4677 }
4678
4679
4680 /** for two given vertices @p v1 and @p v2 search for a clique in the conflict graph that contains these vertices. From
4681  * this clique, we create a bound constraint.
4682  */
4683 static
4685  SCIP* scip, /**< SCIP pointer */
4686  SCIP_DIGRAPH* conflictgraph, /**< conflict graph */
4687  SCIP_SOL* sol, /**< solution to be enforced (NULL for LP solution) */
4688  int v1, /**< first vertex that shall be contained in bound constraint */
4689  int v2, /**< second vertex that shall be contained in bound constraint */
4690  SCIP_VAR* boundvar, /**< bound variable of @p v1 and @p v2 (or NULL if not existent) */
4691  SCIP_Bool extend, /**< should @p v1 and @p v2 be greedily extended to a clique of larger size */
4692  SCIP_CONS* cons, /**< bound constraint */
4693  SCIP_Real* feas /**< feasibility value of bound constraint */
4694  )
4695 {
4696  SCIP_NODEDATA* nodedata;
4698  SCIP_Real solval;
4699  SCIP_VAR* var;
4700  SCIP_Real coef = 0.0;
4701  int nsucc;
4702  int s;
4703
4704  int* extensions = NULL;
4705  int nextensions = 0;
4706  int nextensionsnew;
4707  int* succ;
4708
4709  assert( scip != NULL );
4710  assert( conflictgraph != NULL );
4711  assert( cons != NULL );
4712  assert( feas != NULL );
4713
4714  *feas = 0.0;
4715
4716  /* add index 'v1' to the clique */
4717  nodedata = (SCIP_NODEDATA*)SCIPdigraphGetNodeData(conflictgraph, v1);
4718  var = nodedata->var;
4719  assert( boundvar == NULL || SCIPvarCompare(boundvar, nodedata->ubboundvar) == 0 );
4720  solval = SCIPgetSolVal(scip, sol, var);
4721
4722  /* if 'v1' and 'v2' have the same bound variable then the bound cut can be strengthened */
4723  if ( boundvar == NULL )
4724  {
4725  if ( SCIPisFeasPositive(scip, solval) )
4726  {
4727  SCIP_Real ub;
4728  ub = SCIPvarGetUbLocal(var);
4729  assert( SCIPisFeasPositive(scip, ub));
4730
4731  if ( ! SCIPisInfinity(scip, ub) )
4732  coef = 1.0/ub;
4733  }
4734  else if ( SCIPisFeasNegative(scip, solval) )
4735  {
4736  SCIP_Real lb;
4737  lb = SCIPvarGetLbLocal(var);
4738  assert( SCIPisFeasNegative(scip, lb) );
4739  if ( ! SCIPisInfinity(scip, -lb) )
4740  coef = 1.0/lb;
4741  }
4742  }
4743  else if ( boundvar == nodedata->ubboundvar )
4744  {
4745  if ( SCIPisFeasPositive(scip, solval) )
4746  {
4747  SCIP_Real ub;
4748
4749  ub = nodedata->ubboundcoef;
4750  assert( SCIPisFeasPositive(scip, ub) );
4751  if ( ! SCIPisInfinity(scip, ub) )
4752  coef = 1.0/ub;
4753  }
4754  else if ( SCIPisFeasNegative(scip, solval) )
4755  {
4756  SCIP_Real lb;
4757
4758  lb = nodedata->lbboundcoef;
4759  assert( SCIPisFeasPositive(scip, lb) );
4760  if ( ! SCIPisInfinity(scip, lb) )
4761  coef = 1.0/lb;
4762  }
4763  }
4764
4765  if ( ! SCIPisZero(scip, coef) )
4766  {
4767  *feas += coef * solval;
4768  SCIP_CALL( SCIPaddCoefLinear(scip, cons, var, coef) );
4769  }
4770
4771  /* if clique shall be greedily extended to a clique of larger size */
4772  if ( extend )
4773  {
4774  /* get successors */
4775  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, v1);
4776  succ = SCIPdigraphGetSuccessors(conflictgraph, v1);
4777  assert( nsucc > 0 );
4778
4779  /* allocate buffer array */
4780  SCIP_CALL( SCIPallocBufferArray(scip, &extensions, nsucc) );
4781
4782  /* get possible extensions for the clique cover */
4783  for (s = 0; s < nsucc; ++s)
4784  extensions[s] = succ[s];
4785  nextensions = nsucc;
4786  }
4787  else
4788  nextensions = 1;
4789
4790  /* while there exist possible extensions for the clique cover */
4791  while ( nextensions > 0 )
4792  {
4793  SCIP_Real bestbigMval;
4794  SCIP_Real bigMval;
4795  int bestindex = -1;
4796  int ext;
4797
4798  bestbigMval = -SCIPinfinity(scip);
4799
4800  /* if v2 has not been added to clique already */
4802  {
4803  bestindex = v2;
4805  }
4806  else /* search for the extension with the largest absolute value of its LP relaxation solution value */
4807  {
4808  assert( extensions != NULL );
4809  for (s = 0; s < nextensions; ++s)
4810  {
4811  ext = extensions[s];
4812  bigMval = nodeGetSolvalBinaryBigMSOS1(scip, conflictgraph, sol, ext);
4813  if ( SCIPisFeasLT(scip, bestbigMval, bigMval) )
4814  {
4815  bestbigMval = bigMval;
4816  bestindex = ext;
4817  }
4818  }
4819  }
4820  assert( bestindex != -1 );
4821
4822  /* add bestindex variable to the constraint */
4823  nodedata = (SCIP_NODEDATA*)SCIPdigraphGetNodeData(conflictgraph, bestindex);
4824  var = nodedata->var;
4825  solval = SCIPgetSolVal(scip, sol, var);
4826  coef = 0.0;
4827  if ( boundvar == NULL )
4828  {
4829  if ( SCIPisFeasPositive(scip, solval) )
4830  {
4831  SCIP_Real ub;
4832  ub = SCIPvarGetUbLocal(var);
4833  assert( SCIPisFeasPositive(scip, ub));
4834
4835  if ( ! SCIPisInfinity(scip, ub) )
4836  coef = 1.0/ub;
4837  }
4838  else if ( SCIPisFeasNegative(scip, solval) )
4839  {
4840  SCIP_Real lb;
4841  lb = SCIPvarGetLbLocal(var);
4842  assert( SCIPisFeasNegative(scip, lb) );
4843  if ( ! SCIPisInfinity(scip, -lb) )
4844  coef = 1.0/lb;
4845  }
4846  }
4847  else if ( boundvar == nodedata->ubboundvar )
4848  {
4849  if ( SCIPisFeasPositive(scip, solval) )
4850  {
4851  SCIP_Real ub;
4852
4853  ub = nodedata->ubboundcoef;
4854  assert( SCIPisFeasPositive(scip, ub) );
4855  if ( ! SCIPisInfinity(scip, ub) )
4856  coef = 1.0/ub;
4857  }
4858  else if ( SCIPisFeasNegative(scip, solval) )
4859  {
4860  SCIP_Real lb;
4861
4862  lb = nodedata->lbboundcoef;
4863  assert( SCIPisFeasPositive(scip, lb) );
4864  if ( ! SCIPisInfinity(scip, -lb) )
4865  coef = 1.0/lb;
4866  }
4867  }
4868  if ( ! SCIPisZero(scip, coef) )
4869  {
4870  *feas += coef * solval;
4871  SCIP_CALL( SCIPaddCoefLinear(scip, cons, var, coef) );
4872  }
4873
4874  if ( extend )
4875  {
4876  assert( extensions != NULL );
4877  /* compute new 'extensions' array */
4878  nextensionsnew = 0;
4879  for (s = 0; s < nextensions; ++s)
4880  {
4881  if ( s != bestindex && isConnectedSOS1(NULL, conflictgraph, bestindex, extensions[s]) )
4882  extensions[nextensionsnew++] = extensions[s];
4883  }
4884  nextensions = nextensionsnew;
4885  }
4886  else
4887  nextensions = 0;
4888  }
4889
4890  /* free buffer array */
4891  if ( extend )
4892  SCIPfreeBufferArray(scip, &extensions);
4893
4894  /* subtract rhs of constraint from feasibility value or add bound variable if existent */
4895  if ( boundvar == NULL )
4896  *feas -= 1.0;
4897  else
4898  {
4899  SCIP_CALL( SCIPaddCoefLinear(scip, cons, boundvar, -1.0) );
4900  *feas -= SCIPgetSolVal(scip, sol, boundvar);
4901  }
4902
4903  return SCIP_OKAY;
4904 }
4905
4906
4907 /** tries to add feasible complementarity constraints to a given child branching node.
4908  *
4909  * @note In this function the conflict graph is updated to the conflict graph of the considered child branching node.
4910  */
4911 static
4913  SCIP* scip, /**< SCIP pointer */
4914  SCIP_NODE* node, /**< branching node */
4915  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
4916  SCIP_DIGRAPH* conflictgraph, /**< conflict graph of the current node */
4917  SCIP_DIGRAPH* localconflicts, /**< local conflicts (updates to local conflicts of child node) */
4918  SCIP_SOL* sol, /**< solution to be enforced (NULL for LP solution) */
4919  int nsos1vars, /**< number of SOS1 variables */
4920  SCIP_Bool* verticesarefixed, /**< vector that indicates which variables are currently fixed to zerox */
4921  int* fixingsnode1, /**< vertices of variables that will be fixed to zero for the branching node in the input of this function */
4922  int nfixingsnode1, /**< number of entries of array nfixingsnode1 */
4923  int* fixingsnode2, /**< vertices of variables that will be fixed to zero for the other branching node */
4924  int nfixingsnode2, /**< number of entries of array nfixingsnode2 */
4925  int* naddedconss, /**< pointer to store the number of added SOS1 constraints */
4926  SCIP_Bool onlyviolsos1 /**< should only SOS1 constraints be added that are violated by the LP solution */
4927  )
4928 {
4929  assert( scip != NULL );
4930  assert( node != NULL );
4931  assert( conshdlrdata != NULL );
4932  assert( conflictgraph != NULL );
4933  assert( verticesarefixed != NULL );
4934  assert( fixingsnode1 != NULL );
4935  assert( fixingsnode2 != NULL );
4936  assert( naddedconss != NULL );
4937
4939
4940  if ( nfixingsnode2 > 1 )
4941  {
4942  int* fixingsnode21; /* first partition of fixingsnode2 */
4943  int* fixingsnode22; /* second partition of fixingsnode2 */
4944  int nfixingsnode21;
4945  int nfixingsnode22;
4946
4947  int* coverarray; /* vertices, not in fixingsnode1 that cover all the vertices in array fixingsnode22 */
4948  int ncoverarray;
4949
4950  SCIP_Bool* mark;
4951  int* succarray;
4952  int nsuccarray;
4953  int* succ;
4954  int nsucc;
4955
4956  int i;
4957  int s;
4958
4959  /* allocate buffer arrays */
4960  SCIP_CALL( SCIPallocBufferArray(scip, &succarray, nsos1vars) );
4961  SCIP_CALL( SCIPallocBufferArray(scip, &mark, nsos1vars) );
4962  SCIP_CALL( SCIPallocBufferArray(scip, &fixingsnode21, nfixingsnode2) );
4963  SCIP_CALL( SCIPallocBufferArray(scip, &fixingsnode22, nfixingsnode2) );
4964
4965  /* mark all the unfixed vertices with FALSE */
4966  for (i = 0; i < nsos1vars; ++i)
4967  mark[i] = (verticesarefixed[i]);
4968
4969  /* mark all the vertices that are in the set fixingsnode1 */
4970  for (i = 0; i < nfixingsnode1; ++i)
4971  {
4972  assert( nfixingsnode1 <= 1 || (fixingsnode1[nfixingsnode1 - 1] > fixingsnode1[nfixingsnode1 - 2]) ); /* test: vertices are sorted */
4973  mark[fixingsnode1[i]] = TRUE;
4974  }
4975
4976  /* mark all the vertices that are in the set fixingsnode2 */
4977  for (i = 0; i < nfixingsnode2; ++i)
4978  {
4979  assert( nfixingsnode2 <= 1 || (fixingsnode2[nfixingsnode2 - 1] > fixingsnode2[nfixingsnode2 - 2]) ); /* test: vertices are sorted */
4980  mark[fixingsnode2[i]] = TRUE;
4981  }
4982
4983  /* compute the set of vertices that have a neighbor in the set fixingsnode2, but are not in the set fixingsnode1 or fixingsnode2 and are not already fixed */
4984  nsuccarray = 0;
4985  for (i = 0; i < nfixingsnode2; ++i)
4986  {
4987  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, fixingsnode2[i]);
4988  succ = SCIPdigraphGetSuccessors(conflictgraph, fixingsnode2[i]);
4989
4990  for (s = 0; s < nsucc; ++s)
4991  {
4992  int succnode = succ[s];
4993
4994  if ( ! mark[succnode] )
4995  {
4996  mark[succnode] = TRUE;
4997  succarray[nsuccarray++] = succnode;
4998  }
4999  }
5000  }
5001
5002  /* allocate buffer array */
5003  SCIP_CALL( SCIPallocBufferArray(scip, &coverarray, nsos1vars) );
5004
5005  /* mark all the vertices with FALSE */
5006  for (i = 0; i < nsos1vars; ++i)
5007  mark[i] = FALSE;
5008
5009  /* mark all the vertices that are in the set fixingsnode2 */
5010  for (i = 0; i < nfixingsnode2; ++i)
5011  mark[fixingsnode2[i]] = TRUE;
5012
5013  /* for every node in succarray */
5014  for (i = 0; i < nsuccarray; ++i)
5015  {
5016  SCIP_Real solval1;
5017  SCIP_VAR* var1;
5018  int vertex1;
5019  int j;
5020
5021  vertex1 = succarray[i];
5022  var1 = SCIPnodeGetVarSOS1(conflictgraph, vertex1);
5023  solval1 = SCIPgetSolVal(scip, sol, var1);
5024
5025  /* we only add complementarity constraints if they are violated by the current LP solution */
5026  if ( ! onlyviolsos1 || ! SCIPisFeasZero(scip, solval1) )
5027  {
5028  /* compute first partition of fixingsnode2 that is the intersection of the neighbors of 'vertex1' with the set fixingsnode2 */
5029  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, vertex1);
5030  succ = SCIPdigraphGetSuccessors(conflictgraph, vertex1);
5031  nfixingsnode21 = 0;
5032
5033  for (s = 0; s < nsucc; ++s)
5034  {
5035  if ( mark[succ[s]] )
5036  {
5037  fixingsnode21[nfixingsnode21++] = succ[s];
5038  assert( nfixingsnode21 == 1 || (fixingsnode21[nfixingsnode21 - 1] > fixingsnode21[nfixingsnode21 - 2]) ); /* test: successor vertices are sorted */
5039  }
5040  }
5041
5042  /* if variable can be fixed to zero */
5043  if ( nfixingsnode21 == nfixingsnode2 )
5044  {
5045  SCIP_Bool infeasible;
5046
5047  SCIP_CALL( fixVariableZeroNode(scip, var1, node, &infeasible) );
5048  assert( ! infeasible );
5049  continue;
5050  }
5051
5052  /* compute second partition of fixingsnode2 (that is fixingsnode2 \setminus fixingsnode21 ) */
5053  SCIPcomputeArraysSetminusInt(fixingsnode2, nfixingsnode2, fixingsnode21, nfixingsnode21, fixingsnode22, &nfixingsnode22);
5054  assert ( nfixingsnode22 + nfixingsnode21 == nfixingsnode2 );
5055
5056  /* compute cover set (that are all the vertices not in fixingsnode1 and fixingsnode21, whose neighborhood covers all the vertices of fixingsnode22) */
5057  SCIP_CALL( getCoverVertices(conflictgraph, verticesarefixed, -1, fixingsnode22, nfixingsnode22, coverarray, &ncoverarray) );
5058  SCIPcomputeArraysSetminusInt(coverarray, ncoverarray, fixingsnode1, nfixingsnode1, coverarray, &ncoverarray);
5059  SCIPcomputeArraysSetminusInt(coverarray, ncoverarray, fixingsnode21, nfixingsnode21, coverarray, &ncoverarray);
5060
5061  for (j = 0; j < ncoverarray; ++j)
5062  {
5063  int vertex2;
5064
5065  vertex2 = coverarray[j];
5066  assert( vertex2 != vertex1 );
5067
5068  /* prevent double enumeration */
5069  if ( vertex2 < vertex1 )
5070  {
5071  SCIP_VAR* var2;
5072  SCIP_Real solval2;
5073
5074  var2 = SCIPnodeGetVarSOS1(conflictgraph, vertex2);
5075  solval2 = SCIPgetSolVal(scip, sol, var2);
5076
5077  if ( onlyviolsos1 && ( SCIPisFeasZero(scip, solval1) || SCIPisFeasZero(scip, solval2) ) )
5078  continue;
5079
5080  if ( ! isConnectedSOS1(NULL, conflictgraph, vertex1, vertex2) )
5081  {
5082  char name[SCIP_MAXSTRLEN];
5083  SCIP_CONS* conssos1 = NULL;
5084  SCIP_Bool takebound = FALSE;
5085  SCIP_Real feas;
5086
5087  SCIP_NODEDATA* nodedata;
5088  SCIP_Real lbboundcoef1;
5089  SCIP_Real lbboundcoef2;
5090  SCIP_Real ubboundcoef1;
5091  SCIP_Real ubboundcoef2;
5092  SCIP_VAR* boundvar1;
5093  SCIP_VAR* boundvar2;
5094
5095  /* get bound variables if available */
5096  nodedata = (SCIP_NODEDATA*)SCIPdigraphGetNodeData(conflictgraph, vertex1);
5097  assert( nodedata != NULL );
5098  boundvar1 = nodedata->ubboundvar;
5099  lbboundcoef1 = nodedata->lbboundcoef;
5100  ubboundcoef1 = nodedata->ubboundcoef;
5101  nodedata = (SCIP_NODEDATA*)SCIPdigraphGetNodeData(conflictgraph, vertex2);
5102  assert( nodedata != NULL );
5103  boundvar2 = nodedata->ubboundvar;
5104  lbboundcoef2 = nodedata->lbboundcoef;
5105  ubboundcoef2 = nodedata->ubboundcoef;
5106
5107  if ( boundvar1 != NULL && boundvar2 != NULL && SCIPvarCompare(boundvar1, boundvar2) == 0 )
5108  takebound = TRUE;
5109
5110  /* add new arc to local conflicts in order to generate tighter bound inequalities */
5112  {
5113  if ( localconflicts == NULL )
5114  {
5115  SCIP_CALL( SCIPcreateDigraph(scip, &conshdlrdata->localconflicts, nsos1vars) );
5116  localconflicts = conshdlrdata->localconflicts;
5117  }
5118  SCIP_CALL( SCIPdigraphAddArc(localconflicts, vertex1, vertex2, NULL) );
5119  SCIP_CALL( SCIPdigraphAddArc(localconflicts, vertex2, vertex1, NULL) );
5120  SCIP_CALL( SCIPdigraphAddArc(conflictgraph, vertex1, vertex2, NULL) );
5121  SCIP_CALL( SCIPdigraphAddArc(conflictgraph, vertex2, vertex1, NULL) );
5122
5123  /* can sort successors in place - do not use arcdata */
5124  SCIPsortInt(SCIPdigraphGetSuccessors(localconflicts, vertex1), SCIPdigraphGetNSuccessors(localconflicts, vertex1));
5125  SCIPsortInt(SCIPdigraphGetSuccessors(localconflicts, vertex2), SCIPdigraphGetNSuccessors(localconflicts, vertex2));
5126  SCIPsortInt(SCIPdigraphGetSuccessors(conflictgraph, vertex1), SCIPdigraphGetNSuccessors(conflictgraph, vertex1));
5127  SCIPsortInt(SCIPdigraphGetSuccessors(conflictgraph, vertex2), SCIPdigraphGetNSuccessors(conflictgraph, vertex2));
5128
5129  /* mark conflictgraph as not local such that the new arcs are deleted after currents node processing */
5130  conshdlrdata->isconflocal = TRUE;
5131  }
5132
5133  /* measure feasibility of complementarity between var1 and var2 */
5134  if ( ! takebound )
5135  {
5136  feas = -1.0;
5137  if ( SCIPisFeasPositive(scip, solval1) )
5138  {
5139  assert( SCIPisFeasPositive(scip, SCIPvarGetUbLocal(var1)));
5140  if ( ! SCIPisInfinity(scip, SCIPvarGetUbLocal(var1)) )
5141  feas += solval1/SCIPvarGetUbLocal(var1);
5142  }
5143  else if ( SCIPisFeasNegative(scip, solval1) )
5144  {
5145  assert( SCIPisFeasPositive(scip, SCIPvarGetLbLocal(var1)));
5146  if ( ! SCIPisInfinity(scip, -SCIPvarGetLbLocal(var1)) )
5147  feas += solval1/SCIPvarGetLbLocal(var1);
5148  }
5149
5150  if ( SCIPisFeasPositive(scip, solval2) )
5151  {
5152  assert( SCIPisFeasPositive(scip, SCIPvarGetUbLocal(var2)));
5153  if ( ! SCIPisInfinity(scip, SCIPvarGetUbLocal(var2)) )
5154  feas += solval2/SCIPvarGetUbLocal(var2);
5155  }
5156  else if ( SCIPisFeasNegative(scip, solval2) )
5157  {
5158  assert( SCIPisFeasPositive(scip, SCIPvarGetLbLocal(var2)));
5159  if ( ! SCIPisInfinity(scip, -SCIPvarGetLbLocal(var2)) )
5160  feas += solval2/SCIPvarGetLbLocal(var2);
5161  }
5162  }
5163  else
5164  {
5165  feas = -SCIPgetSolVal(scip, sol, boundvar1);
5166  if ( SCIPisFeasPositive(scip, solval1) )
5167  {
5168  assert( SCIPisFeasPositive(scip, ubboundcoef1));
5169  if ( ! SCIPisInfinity(scip, ubboundcoef1) )
5170  feas += solval1/ubboundcoef1;
5171  }
5172  else if ( SCIPisFeasNegative(scip, solval1) )
5173  {
5174  assert( SCIPisFeasPositive(scip, lbboundcoef1));
5175  if ( ! SCIPisInfinity(scip, -lbboundcoef1) )
5176  feas += solval1/lbboundcoef1;
5177  }
5178
5179  if ( SCIPisFeasPositive(scip, solval2) )
5180  {
5181  assert( SCIPisFeasPositive(scip, ubboundcoef2));
5182  if ( ! SCIPisInfinity(scip, ubboundcoef2) )
5183  feas += solval2/ubboundcoef2;
5184  }
5185  else if ( SCIPisFeasNegative(scip, solval2) )
5186  {
5187  assert( SCIPisFeasPositive(scip, lbboundcoef2));
5188  if ( ! SCIPisInfinity(scip, -lbboundcoef2) )
5189  feas += solval2/lbboundcoef2;
5190  }
5191  assert( ! SCIPisFeasNegative(scip, solval2) );
5192  }
5193
5194  if ( SCIPisGT(scip, feas, conshdlrdata->addcompsfeas) )
5195  {
5196  /* create SOS1 constraint */
5197  (void) SCIPsnprintf(name, SCIP_MAXSTRLEN, "sos1_branchnode_%" SCIP_LONGINT_FORMAT "_no_%i", SCIPnodeGetNumber(node), *naddedconss);
5198  SCIP_CALL( SCIPcreateConsSOS1(scip, &conssos1, name, 0, NULL, NULL, TRUE, TRUE, TRUE, FALSE, TRUE,
5199  TRUE, FALSE, FALSE, FALSE) );
5200
5201  /* add variables to SOS1 constraint */
5202  SCIP_CALL( addVarSOS1(scip, conssos1, conshdlrdata, var1, 1.0) );
5203  SCIP_CALL( addVarSOS1(scip, conssos1, conshdlrdata, var2, 2.0) );
5204
5205  /* add SOS1 constraint to the branching node */
5206  SCIP_CALL( SCIPaddConsNode(scip, node, conssos1, NULL) );
5208
5209  /* release constraint */
5210  SCIP_CALL( SCIPreleaseCons(scip, &conssos1) );
5211  }
5212
5214  if ( ! SCIPisFeasZero(scip, solval1) && ! SCIPisFeasZero(scip, solval2) )
5215  {
5216  /* possibly create linear constraint of the form x_i/u_i + x_j/u_j <= t if a bound variable t with x_i <= u_i * t and x_j <= u_j * t exists.
5217  * Otherwise try to create a constraint of the form x_i/u_i + x_j/u_j <= 1. Try the same for the lower bounds. */
5218  (void) SCIPsnprintf(name, SCIP_MAXSTRLEN, "boundcons_branchnode_%" SCIP_LONGINT_FORMAT "_no_%i", SCIPnodeGetNumber(node), *naddedconss);
5219  if ( takebound )
5220  {
5221  /* create constraint with right hand side = 0.0 */
5222  SCIP_CALL( SCIPcreateConsLinear(scip, &conssos1, name, 0, NULL, NULL, -SCIPinfinity(scip), 0.0, TRUE, FALSE, TRUE, FALSE, FALSE,
5223  TRUE, FALSE, FALSE, FALSE, FALSE) );
5224
5226  SCIP_CALL( getBoundConsFromVertices(scip, conflictgraph, sol, vertex1, vertex2, boundvar1, conshdlrdata->addextendedbds, conssos1, &feas) );
5227  }
5228  else
5229  {
5230  /* create constraint with right hand side = 1.0 */
5231  SCIP_CALL( SCIPcreateConsLinear(scip, &conssos1, name, 0, NULL, NULL, -SCIPinfinity(scip), 1.0, TRUE, FALSE, TRUE, FALSE, FALSE,
5232  TRUE, FALSE, FALSE, FALSE, FALSE) );
5233
5235  SCIP_CALL( getBoundConsFromVertices(scip, conflictgraph, sol, vertex1, vertex2, NULL, conshdlrdata->addextendedbds, conssos1, &feas) );
5236  }
5237
5238  /* add linear constraint to the branching node if usefull */
5239  if ( SCIPisGT(scip, feas, conshdlrdata->addbdsfeas ) )
5240  {
5241  SCIP_CALL( SCIPaddConsNode(scip, node, conssos1, NULL) );
5243  }
5244
5245  /* release constraint */
5246  SCIP_CALL( SCIPreleaseCons(scip, &conssos1) );
5247  }
5248
5249  /* break if number of added constraints exceeds a predefined value */
5251  break;
5252  }
5253  }
5254  }
5255  }
5256
5257  /* break if number of added constraints exceeds a predefined value */
5259  break;
5260  }
5261
5262  /* free buffer array */
5263  SCIPfreeBufferArray(scip, &coverarray);
5264  SCIPfreeBufferArray(scip, &fixingsnode22);
5265  SCIPfreeBufferArray(scip, &fixingsnode21);
5266  SCIPfreeBufferArray(scip, &mark);
5267  SCIPfreeBufferArray(scip, &succarray);
5268  }
5269
5270  return SCIP_OKAY;
5271 }
5272
5273
5274 /** resets local conflict graph to the conflict graph of the root node */
5275 static
5277  SCIP_DIGRAPH* conflictgraph, /**< conflict graph of root node */
5278  SCIP_DIGRAPH* localconflicts, /**< local conflicts that should be removed from conflict graph */
5279  int nsos1vars /**< number of SOS1 variables */
5280  )
5281 {
5282  int j;
5283
5284  for (j = 0; j < nsos1vars; ++j)
5285  {
5286  int nsuccloc;
5287
5288  nsuccloc = SCIPdigraphGetNSuccessors(localconflicts, j);
5289  if ( nsuccloc > 0 )
5290  {
5291  int* succloc;
5292  int* succ;
5293  int nsucc;
5294  int k = 0;
5295
5296  succloc = SCIPdigraphGetSuccessors(localconflicts, j);
5297  succ = SCIPdigraphGetSuccessors(conflictgraph, j);
5298  nsucc = SCIPdigraphGetNSuccessors(conflictgraph, j);
5299
5300  /* reset number of successors */
5301  SCIPcomputeArraysSetminusInt(succ, nsucc, succloc, nsuccloc, succ, &k);
5302  SCIP_CALL( SCIPdigraphSetNSuccessors(conflictgraph, j, k) );
5303  SCIP_CALL( SCIPdigraphSetNSuccessors(localconflicts, j, 0) );
5304  }
5305  }
5306
5307  return SCIP_OKAY;
5308 }
5309
5310
5311 /** Conflict graph enforcement method
5312  *
5313  * The conflict graph can be enforced by different branching rules:
5314  *
5315  * - Branch on the neighborhood of a single variable @p i, i.e., in one branch \f$x_i\f$ is fixed to zero and in the
5316  * other its neighbors from the conflict graph.
5317  *
5318  * - Branch on complete bipartite subgraphs of the conflict graph, i.e., in one branch fix the variables from the first
5319  * bipartite partition and the variables from the second bipartite partition in the other.
5320  *
5321  * - In addition to variable domain fixings, it is sometimes also possible to add new SOS1 constraints to the branching
5322  * nodes. This results in a nonstatic conflict graph, which may change dynamically with every branching node.
5323  *
5324  * We make use of different selection rules that define on which system of SOS1 variables to branch next:
5325  *
5326  * - Most infeasible branching: Branch on the system of SOS1 variables with largest violation.
5327  *
5328  * - Strong branching: Here, the LP-relaxation is partially solved for each branching decision among a candidate list.
5329  * Then the decision with best progress is chosen.
5330  */
5331 static
5333  SCIP* scip, /**< SCIP pointer */
5334  SCIP_CONSHDLRDATA* conshdlrdata, /**< constraint handler data */
5335  SCIP_CONSHDLR* conshdlr, /**< constraint handler */
5336  int nconss, /**< number of constraints */
5337  SCIP_CONS** conss, /**< SOS1 constraints */
5338  SCIP_SOL* sol, /**< solution to be enforced (NULL for LP solution) */
5339  SCIP_RESULT* result /**< result */
5340  )
5341 {
5342  SCIP_DIGRAPH* conflictgraph;
5343  int nsos1vars;
5344
5345  SCIP_Bool* verticesarefixed = NULL;
5346  int* fixingsnode1 = NULL;
5347  int* fixingsnode2 = NULL;
5348  int nfixingsnode1;
5349  int nfixingsnode2;
5350
5351  SCIP_Real bestobjval1 = -SCIPinfinity(scip);
5352  SCIP_Real bestobjval2 = -SCIPinfinity(scip);
5353  SCIP_Real lpobjval = -SCIPinfinity(scip);
5354
5355  SCIP_Bool infeasible;
5356  SCIP_Bool bipbranch = FALSE;
5357  int nstrongrounds;
5358
5359  int branchvertex;
5360  SCIP_NODE* node1;
5361  SCIP_NODE* node2;
5362  SCIP_Real nodeselest;
5363  SCIP_Real objest;
5364
5365  int i;
5366  int j;
5367  int c;
5368
5369  assert( scip != NULL );
5370  assert( conshdlrdata != NULL );
5371  assert( conshdlr != NULL );
5372  assert( conss != NULL );
5373  assert( result != NULL );
5374
5375  SCIPdebugMsg(scip, "Enforcing SOS1 conflict graph <%s>.\n", SCIPconshdlrGetName(conshdlr) );
5376  *result = SCIP_DIDNOTRUN;
5377
5378  /* get number of SOS1 variables */
5379  nsos1vars = conshdlrdata->nsos1vars;
5380
5381  /* exit for trivial cases */
5382  if ( nsos1vars == 0 || nconss == 0 )
5383  {
5384  *result = SCIP_FEASIBLE;
5385  return SCIP_OKAY;
5386  }
5387
5388  /* get conflict graph */
5389  conflictgraph = conshdlrdata->conflictgraph;
5390  assert( ! conshdlrdata->isconflocal ); /* conflictgraph should be the one of the root node */
5391
5392  /* check each constraint and update conflict graph if necessary */
5393  for (c = 0; c < nconss; ++c)
5394  {
5395  SCIP_CONSDATA* consdata;
5396  SCIP_CONS* cons;
5397  SCIP_Bool cutoff;
5398  int ngen = 0;
5399
5400  cons = conss[c];
5401  assert( cons != NULL );
5402  consdata = SCIPconsGetData(cons);
5403  assert( consdata != NULL );
5404
5405  /* do nothing if there are not enough variables - this is usually eliminated by preprocessing */
5406  if ( consdata->nvars < 2 )
5407  continue;
5408
5409  /* first perform propagation (it might happen that standard propagation is turned off) */
5410  SCIP_CALL( propConsSOS1(scip, cons, consdata, &cutoff, &ngen) );
5411  SCIPdebugMsg(scip, "propagating <%s> in enforcing (cutoff: %u, domain reductions: %d).\n", SCIPconsGetName(cons), cutoff, ngen);
5412  if ( cutoff )
5413  {
5414  *result = SCIP_CUTOFF;
5415  break;
5416  }
5417  if ( ngen > 0 )
5418  {
5419  *result = SCIP_REDUCEDDOM;
5420  break;
5421  }
5422  assert( ngen == 0 );
5423
5424  /* add local conflicts to conflict graph and save them in 'localconflicts' */
5425  if ( consdata->local )
5426  {
5427  SCIP_VAR** vars;
5428  int nvars;
5429  int indi;
5430  int indj;
5431
5432  if ( conshdlrdata->localconflicts == NULL )
5433  {
5434  SCIP_CALL( SCIPcreateDigraph(scip, &conshdlrdata->localconflicts, nsos1vars) );
5435  }
5436
5437  vars = consdata->vars;
5438  nvars = consdata->nvars;
5439  for (i = 0; i < nvars-1; ++i)
5440  {
5441  SCIP_VAR* var;
5442
5443  var = vars[i];
5444  indi = varGetNodeSOS1(conshdlrdata, var);
5445
5446  if( indi == -1 )
5447  return SCIP_INVALIDDATA;
5448
5449  if ( ! SCIPisFeasZero(scip, SCIPvarGetUbLocal(var)) || ! SCIPisFeasZero(scip, SCIPvarGetLbLocal(var)) )
5450  {
5451  for (j = i+1; j < nvars; ++j)
5452  {
5453  var = vars[j];
5454  indj = varGetNodeSOS1(conshdlrdata, var);
5455
5456  if( indj == -1 )
5457  return SCIP_INVALIDDATA;
5458
5459  if ( ! SCIPisFeasZero(scip, SCIPvarGetUbLocal(var)) || ! SCIPisFeasZero(scip, SCIPvarGetLbLocal(var)) )
5460  {
5461  if ( ! isConnectedSOS1(NULL, conflictgraph, indi, indj) )
5462  {
5463  SCIP_CALL( SCIPdigraphAddArcSafe(conflictgraph, indi, indj, NULL) );
5464  SCIP_CALL( SCIPdigraphAddArcSafe(conflictgraph, indj, indi, NULL) );
5465
5466  SCIP_CALL( SCIPdigraphAddArcSafe(conshdlrdata->localconflicts, indi, indj, NULL) );
5467  SCIP_CALL( SCIPdigraphAddArcSafe(conshdlrdata->localconflicts, indj, indi, NULL) );
5468
5469  conshdlrdata->isconflocal = TRUE;
5470  }
5471  }
5472  }
5473  }
5474  }
5475  }
5476  }
5477
5478  /* sort successor list of conflict graph if necessary */
5479  if ( conshdlrdata->isconflocal )
5480  {
5481  for (j = 0; j < nsos1vars; ++j)
5482  {
5483  int nsuccloc;
5484
5485  nsuccloc = SCIPdigraphGetNSuccessors(conshdlrdata->localconflicts, j);
5486  if ( nsuccloc > 0 )
5487  {
5488  SCIPsortInt(SCIPdigraphGetSuccessors(conflictgraph, j), SCIPdigraphGetNSuccessors(conflictgraph, j));
5489  SCIPsortInt(SCIPdigraphGetSuccessors(conshdlrdata->localconflicts, j), nsuccloc);
5490  }
5491  }
5492  }
5493
5494  if ( *result == SCIP_CUTOFF || *result == SCIP_REDUCEDDOM )
5495  {
5496  /* remove local conflicts from conflict graph */
5497  if ( conshdlrdata->isconflocal )
5498  {
5499  SCIP_CALL( resetConflictgraphSOS1(conflictgraph, conshdlrdata->localconflicts, nsos1vars) );
5500  conshdlrdata->isconflocal = FALSE;
5501  }
5502  return SCIP_OKAY;
5503  }
5504
5505  /* detect fixed variables */
5506  SCIP_CALL( SCIPallocBufferArray(scip, &verticesarefixed, nsos1vars) );
5507  for (j = 0; j < nsos1vars; ++j)
5508  {
5509  SCIP_VAR* var;
5510  SCIP_Real ub;
5511  SCIP_Real lb;
5512
5513  var = SCIPnodeGetVarSOS1(conflictgraph, j);
5514  ub = SCIPvarGetUbLocal(var);
5515  lb = SCIPvarGetLbLocal(var);
5516  if ( SCIPisFeasZero(scip, ub) && SCIPisFeasZero(scip, lb) )
5517  verticesarefixed[j] = TRUE;
5518  else
5519  verticesarefixed[j] = FALSE;
5520  }
5521
5522  /* should bipartite branching be used? */
5523  if ( conshdlrdata->branchingrule == 'b' )
5524  bipbranch = TRUE;
5525
5526  /* determine number of strong branching iterations */
5527  if ( conshdlrdata->nstrongrounds >= 0 )
5528  nstrongrounds = MIN(conshdlrdata->nstrongrounds, nsos1vars);
5529  else
5530  {
5531  /* determine number depending on depth, based on heuristical considerations */
5532  if ( SCIPgetDepth(scip) <= 10 )
5533  nstrongrounds = MAX(10, (int)SCIPfloor(scip, pow(log((SCIP_Real)nsos1vars), 1.0)));/*lint !e666*/
5534  else if ( SCIPgetDepth(scip) <= 20 )
5535  nstrongrounds = MAX(5, (int)SCIPfloor(scip, pow(log((SCIP_Real)nsos1vars), 0.7)));/*lint !e666*/
5536  else
5537  nstrongrounds = 0;
5538  nstrongrounds = MIN(nsos1vars, nstrongrounds);
5539  }
5540
5541  /* allocate buffer arrays */
5542  SCIP_CALL( SCIPallocBufferArray(scip, &fixingsnode1, nsos1vars) );
5543  if ( bipbranch )
5544  SCIP_CALL( SCIPallocBufferArray(scip, &fixingsnode2, nsos1vars) );
5545  else
5546  SCIP_CALL( SCIPallocBufferArray(scip, &fixingsnode2, 1) );
5547
5548  /* if strongbranching is turned off: use most infeasible branching */
5549  if ( nstrongrounds == 0 )
5550  {
5551  SCIP_Bool relsolfeas;
5552
5553  /* get branching vertex using most infeasible branching */
5554  SCIP_CALL( getBranchingPrioritiesSOS1(scip, conshdlrdata, conflictgraph, sol, nsos1vars, verticesarefixed,
5555  bipbranch, fixingsnode1, fixingsnode2, NULL, &branchvertex, &relsolfeas) );
5556
5557  /* if LP relaxation solution is feasible */
5558  if ( relsolfeas )
5559  {
5560  SCIPdebugMsg(scip, "all the SOS1 constraints are feasible.\n");
5561
5562  /* update result */
5563  *result = SCIP_FEASIBLE;
5564
5565  /* remove local conflicts from conflict graph */
5566  if ( conshdlrdata->isconflocal )
5567  {
5568  SCIP_CALL( resetConflictgraphSOS1(conflictgraph, conshdlrdata->localconflicts, nsos1vars) );
5569  conshdlrdata->isconflocal = FALSE;
5570  }
5571
5572  /* free memory */
5573  SCIPfreeBufferArrayNull(scip, &fixingsnode2);
5574  SCIPfreeBufferArrayNull(scip, &fixingsnode1);
5575  SCIPfreeBufferArrayNull(scip, &verticesarefixed);
5576
5577  return SCIP_OKAY;
5578  }
5579  }
5580  else
5581  {
5582  /* get branching vertex using strong branching */
5583  SCIP_CALL( getBranchingDecisionStrongbranchSOS1(scip, conshdlrdata, conflictgraph, sol, nsos1vars, lpobjval,
5584  bipbranch, nstrongrounds, verticesarefixed, fixingsnode1, fixingsnode2, &branchvertex, &bestobjval1,
5585  &bestobjval2, result) );
5586
5587  if ( *result == SCIP_CUTOFF || *result == SCIP_FEASIBLE || *result == SCIP_REDUCEDDOM )
5588  {
5589  /* remove local conflicts from conflict graph */
5590  if ( conshdlrdata->isconflocal )
5591  {
5592  SCIP_CALL( resetConflictgraphSOS1(conflictgraph, conshdlrdata->localconflicts, nsos1vars) );
5593  conshdlrdata->isconflocal = FALSE;
5594  }
5595
5596  /* free memory */
5597  SCIPfreeBufferArrayNull(scip, &fixingsnode2);
5598  SCIPfreeBufferArrayNull(scip, &fixingsnode1);
5599  SCIPfreeBufferArrayNull(scip, &verticesarefixed);
5600
5601  return SCIP_OKAY;
5602  }
5603  }
5604
5605  /* if we should leave branching decision to branching rules */
5606  if ( ! conshdlrdata->branchsos )
5607  {
5608  /* remove local conflicts from conflict graph */
5609  if ( conshdlrdata->isconflocal )
5610  {
5611  SCIP_CALL( resetConflictgraphSOS1(conflictgraph, conshdlrdata->localconflicts, nsos1vars) );
5612  conshdlrdata->isconflocal = FALSE;
5613  }
5614
5615  /* free memory */
5616  SCIPfreeBufferArrayNull(scip, &fixingsnode2);
5617  SCIPfreeBufferArrayNull(scip, &fixingsnode1);
5618  SCIPfreeBufferArrayNull(scip, &verticesarefixed);
5619
5620  assert( branchvertex >= 0 && branchvertex < nsos1vars );
5621  if ( SCIPvarIsBinary(SCIPnodeGetVarSOS1(conflictgraph, branchvertex)) )
5622  {
5623  *result = SCIP_INFEASIBLE;
5624  return SCIP_OKAY;
5625  }
5626  else
5627  {
5628  SCIPerrorMessage("Incompatible parameter setting: branchsos can only be set to false if all SOS1 variables are binary.\n");
5629  return SCIP_PARAMETERWRONGVAL;
5630  }
5631  }
5632
5633  /* create branching nodes */
5634
5635  /* get vertices of variables that will be fixed to zero for each node */
5636  assert( branchvertex >= 0 && branchvertex < nsos1vars );
5637  assert( ! verticesarefixed[branchvertex] );
5638  SCIP_CALL( getBranchingVerticesSOS1(scip, conflictgraph, sol, verticesarefixed, bipbranch, branchvertex,
5639  fixingsnode1, &nfixingsnode1, fixingsnode2, &nfixingsnode2) );
5640
5641  /* calculate node selection and objective estimate for node 1 */
5642  nodeselest = 0.0;
5643  objest = SCIPgetLocalTransEstimate(scip);
5644  for (j = 0; j < nfixingsnode1; ++j)
5645  {
5646  SCIP_VAR* var;
5647
5648  var = SCIPnodeGetVarSOS1(conflictgraph, fixingsnode1[j]);
5649  objest += SCIPcalcChildEstimateIncrease(scip, var, SCIPgetSolVal(scip, sol, var), 0.0);
5650  nodeselest += SCIPcalcNodeselPriority(scip, var, SCIP_BRANCHDIR_DOWNWARDS, 0.0);
5651  }
5652  assert( objest >= SCIPgetLocalTransEstimate(scip) );
5653
5654  /* create node 1 */
5655  SCIP_CALL( SCIPcreateChild(scip, &node1, nodeselest, objest) );
5656
5657  /* fix variables for the first node */
5658  if ( conshdlrdata->fixnonzero && nfixingsnode2 == 1 )
5659  {
5660  SCIP_VAR* var;
5661  SCIP_Real lb;
5662  SCIP_Real ub;
5663
5664  var = SCIPnodeGetVarSOS1(conflictgraph, fixingsnode2[0]);
5665  lb = SCIPvarGetLbLocal(var);
5666  ub = SCIPvarGetUbLocal(var);
5667
5669  {
5670  if ( SCIPisZero(scip, lb) )
5671  {
5672  /* fix variable to some very small, but positive number or to 1.0 if variable is integral */
5673  if (SCIPvarIsIntegral(var) )
5674  {
5675  SCIP_CALL( SCIPchgVarLbNode(scip, node1, var, 1.0) );
5676  }
5677  else
5678  {
5679  SCIP_CALL( SCIPchgVarLbNode(scip, node1, var, 1.5 * SCIPfeastol(scip)) );
5680  }
5681  }
5682  else if ( SCIPisZero(scip, ub) )
5683  {
5684  if (SCIPvarIsIntegral(var) )
5685  {
5686  /* fix variable to some negative number with small absolute value to -1.0 if variable is integral */
5687  SCIP_CALL( SCIPchgVarUbNode(scip, node1, var, -1.0) );
5688  }
5689  else
5690  {
5691  /* fix variable to some negative number with small absolute value to -1.0 if variable is integral */
5692  SCIP_CALL( SCIPchgVarUbNode(scip, node1, var, -1.5 * SCIPfeastol(scip)) );
5693  }
5694  }
5695  }
5696  }
5697
5698  for (j = 0; j < nfixingsnode1; ++j)
5699  {
5700  /* fix variable to zero */
5701  SCIP_CALL( fixVariableZeroNode(scip, SCIPnodeGetVarSOS1(conflictgraph, fixingsnode1[j]), node1, &infeasible) );
5702  assert( ! infeasible );
5703  }
5704
5705  /* calculate node selection and objective estimate for node 2 */
5706  nodeselest = 0.0;
5707  objest = SCIPgetLocalTransEstimate(scip);
5708  for (j = 0; j < nfixingsnode2; ++j)
5709  {
5710  SCIP_VAR* var;
5711
5712  var = SCIPnodeGetVarSOS1(conflictgraph, fixingsnode1[j]);
5713  objest += SCIPcalcChildEstimateIncrease(scip, var, SCIPgetSolVal(scip, sol, var), 0.0);
5714  nodeselest += SCIPcalcNodeselPriority(scip, var, SCIP_BRANCHDIR_DOWNWARDS, 0.0);
5715  }
5716  assert( objest >= SCIPgetLocalTransEstimate(scip) );
5717
5718  /* create node 2 */
5719  SCIP_CALL( SCIPcreateChild(scip, &node2, nodeselest, objest) );
5720
5721  /* fix variables to zero */
5722  for (j = 0; j < nfixingsnode2; ++j)
5723  {
5724  SCIP_CALL( fixVariableZeroNode(scip, SCIPnodeGetVarSOS1(conflictgraph, fixingsnode2[j]), node2, &infeasible) );
5725  assert( ! infeasible );
5726  }
5727
5728  /* add complementarity constraints to the branching nodes */
5730  {
5732
5733  assert( ! conshdlrdata->fixnonzero );
5734
5735  /* add complementarity constraints to the left branching node */
5736  SCIP_CALL( addBranchingComplementaritiesSOS1(scip, node1, conshdlrdata, conflictgraph, conshdlrdata->localconflicts, sol,
5737  nsos1vars, verticesarefixed, fixingsnode1, nfixingsnode1, fixingsnode2, nfixingsnode2, &naddedconss, TRUE) );
5738
5739  if ( naddedconss == 0 )
5740  {
5741  /* add complementarity constraints to the right branching node */
5742  SCIP_CALL( addBranchingComplementaritiesSOS1(scip, node2, conshdlrdata, conflictgraph, conshdlrdata->localconflicts, sol,
5743  nsos1vars, verticesarefixed, fixingsnode2, nfixingsnode2, fixingsnode1, nfixingsnode1, &naddedconss, TRUE) );
5744  }
5745  }
5746
5747  /* sets node's lower bound to the best known value */
5748  if ( nstrongrounds > 0 )
5749  {
5750  SCIP_CALL( SCIPupdateNodeLowerbound(scip, node1, MAX(lpobjval, bestobjval1) ) );
5751  SCIP_CALL( SCIPupdateNodeLowerbound(scip, node2, MAX(lpobjval, bestobjval2) ) );
5752  }
5753
5754  /* remove local conflicts from conflict graph */
5755  if ( conshdlrdata->isconflocal )
5756  {
5757  SCIP_CALL( resetConflictgraphSOS1(conflictgraph, conshdlrdata->localconflicts, nsos1vars) );
5758  conshdlrdata->isconflocal = FALSE;
5759  }
5760
5761  /* free buffer arrays */
5762  SCIPfreeBufferArrayNull(scip, &fixingsnode2);
5763  SCIPfreeBufferArrayNull(scip, &fixingsnode1);
5764  SCIPfreeBufferArrayNull(scip, &verticesarefixed );
5765  *result = SCIP_BRANCHED;
5766
5767  return SCIP_OKAY;
5768 }
5769
5770
5771 /** SOS1 branching enforcement method
5772  *
5773  * We check whether the current solution is feasible, i.e., contains at most one nonzero
5774  * variable. If not, we branch along the lines indicated by Beale and Tomlin:
5775  *
5776  * We first compute \f$W = \sum_{j=1}^n |x_i|\f$ and \f$w = \sum_{j=1}^n j\, |x_i|\f$. Then we
5777  * search for the index \f$k\f$ that satisfies
5778  * \f[
5779  * k \leq \frac{w}{W} < k+1.
5780  * \f]
5781  * The branches are then
5782  * \f[
5783  * x_1 = 0, \ldots, x_k = 0 \qquad \mbox{and}\qquad x_{k+1} = 0, \ldots, x_n = 0.
5784  * \f]
5785  *
5786  * If the constraint contains two variables, the branching of course simplifies.
5787  *
5788  * Depending on the parameters (@c branchnonzeros, @c branchweight) there are three ways to choose
5789  * the branching constraint.
5790  *
5791  * <TABLE>
5792  * <TR><TD>@c branchnonzeros</TD><TD>@c branchweight</TD><TD>constraint chosen</TD></TR>
5793  * <TR><TD>@c true </TD><TD> ? </TD><TD>most number of nonzeros</TD></TR>
5794  * <TR><TD>@c false </TD><TD> @c true </TD><TD>maximal weight corresponding to nonzero variable</TD></TR>
5795  * <TR><TD>@c false </TD><TD> @c true </TD><TD>largest sum of variable values</TD></TR>
5796  * </TABLE>
5797  *
5798  * @c branchnonzeros = @c false, @c branchweight = @c true allows the user to specify an order for
5799  * the branching importance of the constraints (setting the weights accordingly).
5800  *
5801  * Constraint branching can also be turned off using parameter @c branchsos.
5802  */
5803 static
5805  SCIP* scip, /**< SCIP pointer */
5806  SCIP_CONSHDLR* conshdlr, /**< constraint handler */
5807  int nconss, /**< number of constraints */
5808  SCIP_CONS** conss, /**< indicator constraints */
5809  SCIP_SOL* sol, /**< solution to be enforced (NULL for LP solution) */
5810  SCIP_RESULT* result /**< result */
5811  )
5812 {
5813  SCIP_CONSHDLRDATA* conshdlrdata;
5814  SCIP_CONSDATA* consdata;
5815  SCIP_NODE* node1;
5816  SCIP_NODE* node2;
5818  SCIP_Real maxWeight;
5819  SCIP_VAR** vars;
5820  int nvars;
5821  int c;
5822
5823  assert( scip != NULL );
5824  assert( conshdlr != NULL );
5825  assert( conss != NULL );
5826  assert( result != NULL );
5827
5828  maxWeight = -SCIP_REAL_MAX;
5829  branchCons = NULL;
5830
5831  SCIPdebugMsg(scip, "Enforcing SOS1 constraints <%s>.\n", SCIPconshdlrGetName(conshdlr) );
5832  *result = SCIP_FEASIBLE;
5833
5834  /* get constraint handler data */
5835  conshdlrdata = SCIPconshdlrGetData(conshdlr);
5836  assert( conshdlrdata != NULL );
5837
5838  /* check each constraint */
5839  for (c = 0; c < nconss; ++c)
5840  {
5841  SCIP_CONS* cons;
5842  SCIP_Bool cutoff;
5843  SCIP_Real weight;
5844  int ngen;
5845  int cnt;
5846  int j;
5847
5848  cons = conss[c];
5849  assert( cons != NULL );
5850  consdata = SCIPconsGetData(cons);
5851  assert( consdata != NULL );
5852
5853  ngen = 0;
5854  cnt = 0;
5855  nvars = consdata->nvars;
5856  vars = consdata->vars;
5857
5858  /* do nothing if there are not enough variables - this is usually eliminated by preprocessing */
5859  if ( nvars < 2 )
5860  continue;
5861
5862  /* first perform propagation (it might happen that standard propagation is turned off) */
5863  SCIP_CALL( propConsSOS1(scip, cons, consdata, &cutoff, &ngen) );
5864  SCIPdebugMsg(scip, "propagating <%s> in enforcing (cutoff: %u, domain reductions: %d).\n", SCIPconsGetName(cons), cutoff, ngen);
5865  if ( cutoff )
5866  {
5867  *result = SCIP_CUTOFF;
5868  return SCIP_OKAY;
5869  }
5870  if ( ngen > 0 )
5871  {
5872  *result = SCIP_REDUCEDDOM;
5873  return SCIP_OKAY;
5874  }
5875  assert( ngen == 0 );
5876
5877  /* check constraint */
5878  weight = 0.0;
5879  for (j = 0; j < nvars; ++j)
5880  {
5881  SCIP_Real val = REALABS(SCIPgetSolVal(scip, sol, vars[j]));
5882
5883  if ( ! SCIPisFeasZero(scip, val) )
5884  {
5885  if ( conshdlrdata->branchnonzeros )
5886  weight += 1.0;
5887  else
5888  {
5889  if ( conshdlrdata->branchweight && consdata->weights != NULL )
5890  {
5891  /* choose maximum nonzero-variable weight */
5892  if ( consdata->weights[j] > weight )
5893  weight = consdata->weights[j];
5894  }
5895  else
5896  weight += val;
5897  }
5898  ++cnt;
5899  }
5900  }
5901  /* if constraint is violated */
5902  if ( cnt > 1 && weight > maxWeight )
5903  {
5904  maxWeight = weight;
5905  branchCons = cons;
5906  }
5907  }
5908
5909  /* if all constraints are feasible */
5910  if ( branchCons == NULL )
5911  {
5912  SCIPdebugMsg(scip, "All SOS1 constraints are feasible.\n");
5913  return SCIP_OKAY;
5914  }
5915
5916  /* if we should leave branching decision to branching rules */
5917  if ( ! conshdlrdata->branchsos )
5918  {
5919  int j;
5920
5921  consdata = SCIPconsGetData(branchCons);
5922  for (j = 0; j < consdata->nvars; ++j)
5923  {
5924  if ( ! SCIPvarIsBinary(consdata->vars[j]) )
5925  break;
5926  }
5927
5928  if ( j == consdata->nvars )
5929  {
5930  *result = SCIP_INFEASIBLE;
5931  return SCIP_OKAY;
5932  }
5933  else
5934  {
5935  SCIPerrorMessage("Incompatible parameter setting: branchsos can only be set to false if all SOS1 variables are binary.\n");