Scippy

SCIP

Solving Constraint Integer Programs

heur_twoopt.c
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1 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2 /* */
3 /* This file is part of the program and library */
4 /* SCIP --- Solving Constraint Integer Programs */
5 /* */
6 /* Copyright (C) 2002-2021 Konrad-Zuse-Zentrum */
7 /* fuer Informationstechnik Berlin */
8 /* */
9 /* SCIP is distributed under the terms of the ZIB Academic License. */
10 /* */
11 /* You should have received a copy of the ZIB Academic License */
12 /* along with SCIP; see the file COPYING. If not visit scipopt.org. */
13 /* */
14 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
15 
16 /**@file heur_twoopt.c
17  * @ingroup DEFPLUGINS_HEUR
18  * @brief primal heuristic to improve incumbent solution by flipping pairs of variables
19  * @author Timo Berthold
20  * @author Gregor Hendel
21  */
22 
23 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
24 
25 #include "blockmemshell/memory.h"
26 #include "scip/heur_twoopt.h"
27 #include "scip/pub_heur.h"
28 #include "scip/pub_lp.h"
29 #include "scip/pub_message.h"
30 #include "scip/pub_misc.h"
31 #include "scip/pub_misc_sort.h"
32 #include "scip/pub_sol.h"
33 #include "scip/pub_var.h"
34 #include "scip/scip_heur.h"
35 #include "scip/scip_lp.h"
36 #include "scip/scip_mem.h"
37 #include "scip/scip_message.h"
38 #include "scip/scip_numerics.h"
39 #include "scip/scip_param.h"
40 #include "scip/scip_prob.h"
41 #include "scip/scip_randnumgen.h"
42 #include "scip/scip_sol.h"
43 #include "scip/scip_solvingstats.h"
44 #include <string.h>
45 
46 #define HEUR_NAME "twoopt"
47 #define HEUR_DESC "primal heuristic to improve incumbent solution by flipping pairs of variables"
48 #define HEUR_DISPCHAR SCIP_HEURDISPCHAR_ITERATIVE
49 #define HEUR_PRIORITY -20100
50 #define HEUR_FREQ -1
51 #define HEUR_FREQOFS 0
52 #define HEUR_MAXDEPTH -1
53 
54 #define HEUR_TIMING SCIP_HEURTIMING_AFTERNODE
55 #define HEUR_USESSUBSCIP FALSE /**< does the heuristic use a secondary SCIP instance? */
56 
57 /* default parameter values */
58 #define DEFAULT_INTOPT FALSE /**< optional integer optimization is applied by default */
59 #define DEFAULT_WAITINGNODES 0 /**< default number of nodes to wait after current best solution before calling heuristic */
60 #define DEFAULT_MATCHINGRATE 0.5 /**< default percentage by which two variables have to match in their LP-row set to be
61  * associated as pair by heuristic */
62 #define DEFAULT_MAXNSLAVES 199 /**< default number of slave candidates for a master variable */
63 #define DEFAULT_ARRAYSIZE 10 /**< the default array size for temporary arrays */
64 #define DEFAULT_RANDSEED 37 /**< initial random seed */
65 
66 /*
67  * Data structures
68  */
69 
70 /** primal heuristic data */
71 struct SCIP_HeurData
72 {
73  int lastsolindex; /**< index of last solution for which heuristic was performed */
74  SCIP_Real matchingrate; /**< percentage by which two variables have have to match in their LP-row
75  * set to be associated as pair by heuristic */
76  SCIP_VAR** binvars; /**< Array of binary variables which are sorted with respect to their occurrence
77  * in the LP-rows */
78  int nbinvars; /**< number of binary variables stored in heuristic array */
79  int waitingnodes; /**< user parameter to determine number of nodes to wait after last best solution
80  * before calling heuristic */
81  SCIP_Bool presolved; /**< flag to indicate whether presolving has already been executed */
82  int* binblockstart; /**< array to store the start indices of each binary block */
83  int* binblockend; /**< array to store the end indices of each binary block */
84  int nbinblocks; /**< number of blocks */
85 
86  /* integer variable twoopt data */
87  SCIP_Bool intopt; /**< parameter to determine if integer 2-opt should be applied */
88  SCIP_VAR** intvars; /**< array to store the integer variables in non-decreasing order
89  * with respect to their objective coefficient */
90  int nintvars; /**< the number of integer variables stored in array intvars */
91  int* intblockstart; /**< array to store the start indices of each binary block */
92  int* intblockend; /**< array to store the end indices of each binary block */
93  int nintblocks; /**< number of blocks */
94 
95  SCIP_Bool execute; /**< has presolveTwoOpt detected necessary structure for execution of heuristic? */
96  SCIP_RANDNUMGEN* randnumgen; /**< random number generator */
97  int maxnslaves; /**< delimits the maximum number of slave candidates for a master variable */
98 
99 #ifdef SCIP_STATISTIC
100  /* statistics */
101  int ntotalbinvars; /**< total number of binary variables over all runs */
102  int ntotalintvars; /**< total number of Integer variables over all runs */
103  int nruns; /**< counts the number of runs, i.e. the number of initialized
104  * branch and bound processes */
105  int maxbinblocksize; /**< maximum size of a binary block */
106  int maxintblocksize; /**< maximum size of an integer block */
107  int binnblockvars; /**< number of binary variables that appear in blocks */
108  int binnblocks; /**< number of blocks with at least two variables */
109  int intnblockvars; /**< number of Integer variables that appear in blocks */
110  int intnblocks; /**< number of blocks with at least two variables */
111  int binnexchanges; /**< number of executed changes of binary solution values leading to
112  * improvement in objective function */
113  int intnexchanges; /**< number of executed changes of Integer solution values leading to improvement in
114  * objective function */
115 #endif
116 };
117 
118 /** indicator for optimizing for binaries or integer variables */
119 enum Opttype
120 {
121  OPTTYPE_BINARY = 1,
123 };
124 typedef enum Opttype OPTTYPE;
126 /** indicator for direction of shifting variables */
127 enum Direction
128 {
129  DIRECTION_UP = 1,
132 };
133 typedef enum Direction DIRECTION;
135 /*
136  * Local methods
137  */
138 
139 /** Tries to switch the values of two binary or integer variables and checks feasibility with respect to the LP.
140  *
141  * @todo Adapt method not to copy entire activities array, but only the relevant region.
142  */
143 static
145  SCIP* scip, /**< scip instance */
146  SCIP_VAR* master, /**< first variable of variable pair */
147  SCIP_VAR* slave, /**< second variable of pair */
148  SCIP_Real mastersolval, /**< current value of variable1 in solution */
149  DIRECTION masterdir, /**< the direction into which the master variable has to be shifted */
150  SCIP_Real slavesolval, /**< current value of variable2 in solution */
151  DIRECTION slavedir, /**< the direction into which the slave variable has to be shifted */
152  SCIP_Real shiftval, /**< the value that variables should be shifted by */
153  SCIP_Real* activities, /**< the LP-row activities */
154  int nrows, /**< size of activities array */
155  SCIP_Bool* feasible /**< set to true if method has successfully switched the variable values */
156  )
157 { /*lint --e{715}*/
158  SCIP_COL* col;
159  SCIP_ROW** masterrows;
160  SCIP_ROW** slaverows;
161  SCIP_Real* mastercolvals;
162  SCIP_Real* slavecolvals;
163  int ncolmasterrows;
164  int ncolslaverows;
165  int i;
166  int j;
167 
168  assert(scip != NULL);
169  assert(master != NULL);
170  assert(slave != NULL);
171  assert(activities != NULL);
172  assert(SCIPisFeasGT(scip, shiftval, 0.0));
173 
174  assert(SCIPisFeasGE(scip, mastersolval + (int)masterdir * shiftval, SCIPvarGetLbGlobal(master)));
175  assert(SCIPisFeasLE(scip, mastersolval + (int)masterdir * shiftval, SCIPvarGetUbGlobal(master)));
176 
177  assert(SCIPisFeasGE(scip, slavesolval + (int)slavedir * shiftval, SCIPvarGetLbGlobal(slave)));
178  assert(SCIPisFeasLE(scip, slavesolval + (int)slavedir * shiftval, SCIPvarGetUbGlobal(slave)));
179 
180  /* get variable specific rows and coefficients for both master and slave. */
181  col = SCIPvarGetCol(master);
182  masterrows = SCIPcolGetRows(col);
183  mastercolvals = SCIPcolGetVals(col);
184  ncolmasterrows = SCIPcolGetNNonz(col);
185  assert(ncolmasterrows == 0 || masterrows != NULL);
186 
187  col = SCIPvarGetCol(slave);
188  slaverows = SCIPcolGetRows(col);
189  slavecolvals = SCIPcolGetVals(col);
190  ncolslaverows = SCIPcolGetNNonz(col);
191  assert(ncolslaverows == 0 || slaverows != NULL);
192 
193  /* update the activities of the LP rows of the master variable */
194  for( i = 0; i < ncolmasterrows && SCIProwGetLPPos(masterrows[i]) >= 0; ++i )
195  {
196  int rowpos;
197 
198  rowpos = SCIProwGetLPPos(masterrows[i]);
199  assert(rowpos < nrows);
200 
201  /* skip local rows */
202  if( rowpos >= 0 && ! SCIProwIsLocal(masterrows[i]) )
203  activities[rowpos] += mastercolvals[i] * (int)masterdir * shiftval;
204  }
205 
206  /* update the activities of the LP rows of the slave variable */
207  for( j = 0; j < ncolslaverows && SCIProwGetLPPos(slaverows[j]) >= 0; ++j )
208  {
209  int rowpos;
210 
211  rowpos = SCIProwGetLPPos(slaverows[j]);
212  assert(rowpos < nrows);
213 
214  /* skip local rows */
215  if( rowpos >= 0 && ! SCIProwIsLocal(slaverows[j]) )
216  {
217  activities[rowpos] += slavecolvals[j] * (int)slavedir * shiftval;
218  assert(SCIPisFeasGE(scip, activities[rowpos], SCIProwGetLhs(slaverows[j])));
219  assert(SCIPisFeasLE(scip, activities[rowpos], SCIProwGetRhs(slaverows[j])));
220  }
221  }
222 
223  /* in debug mode, the master rows are checked for feasibility which should be granted by the
224  * decision for a shift value */
225 #ifndef NDEBUG
226  for( i = 0; i < ncolmasterrows && SCIProwGetLPPos(masterrows[i]) >= 0; ++i )
227  {
228  /* local rows can be skipped */
229  if( SCIProwIsLocal(masterrows[i]) )
230  continue;
231 
232  assert(SCIPisFeasGE(scip, activities[SCIProwGetLPPos(masterrows[i])], SCIProwGetLhs(masterrows[i])));
233  assert(SCIPisFeasLE(scip, activities[SCIProwGetLPPos(masterrows[i])], SCIProwGetRhs(masterrows[i])));
234  }
235 #endif
236 
237  *feasible = TRUE;
238 
239  return SCIP_OKAY;
240 }
241 
242 /** Compare two variables with respect to their columns.
243  *
244  * Columns are treated as {0,1} vector, where every nonzero entry is treated as '1', and compared to each other
245  * lexicographically. I.e. var1 is < var2 if the corresponding column of var2 has the smaller single nonzero index of
246  * the two columns. This comparison costs O(constraints) in the worst case
247  */
248 static
249 int varColCompare(
250  SCIP_VAR* var1, /**< left argument of comparison */
251  SCIP_VAR* var2 /**< right argument of comparison */
252  )
253 {
254  SCIP_COL* col1;
255  SCIP_COL* col2;
256  SCIP_ROW** rows1;
257  SCIP_ROW** rows2;
258  int nnonzeros1;
259  int nnonzeros2;
260  int i;
261 
262  assert(var1 != NULL);
263  assert(var2 != NULL);
264 
265  /* get the necessary row and column data */
266  col1 = SCIPvarGetCol(var1);
267  col2 = SCIPvarGetCol(var2);
268  rows1 = SCIPcolGetRows(col1);
269  rows2 = SCIPcolGetRows(col2);
270  nnonzeros1 = SCIPcolGetNNonz(col1);
271  nnonzeros2 = SCIPcolGetNNonz(col2);
272 
273  assert(nnonzeros1 == 0 || rows1 != NULL);
274  assert(nnonzeros2 == 0 || rows2 != NULL);
275 
276  /* loop over the rows, stopped as soon as they differ in one index,
277  * or if counter reaches the end of a variables row set */
278  for( i = 0; i < nnonzeros1 && i < nnonzeros2; ++i )
279  {
280  if( SCIProwGetIndex(rows1[i]) != SCIProwGetIndex(rows2[i]) )
281  return SCIProwGetIndex(rows1[i]) - SCIProwGetIndex(rows2[i]);
282  }
283 
284  /* loop is finished, without differing in one of common row indices, due to loop invariant
285  * variable i reached either nnonzeros1 or nnonzeros2 or both.
286  * one can easily check that the difference of these two numbers always has the desired sign for comparison. */
287  return nnonzeros2 - nnonzeros1 ;
288 }
289 
290 /** implements a comparator to compare two variables with respect to their column entries */
291 static
292 SCIP_DECL_SORTPTRCOMP(SCIPvarcolComp)
293 {
294  return varColCompare((SCIP_VAR*) elem1, (SCIP_VAR*) elem2);
295 }
296 
297 /** checks if two given variables are contained in common LP rows,
298  * returns true if variables share the necessary percentage (matchingrate) of rows.
299  */
300 static
302  SCIP* scip, /**< current SCIP instance */
303  SCIP_VAR* var1, /**< first variable */
304  SCIP_VAR* var2, /**< second variable */
305  SCIP_Real matchingrate /**< determines the ratio of shared LP rows compared to the total number of
306  * LP-rows each variable appears in */
307  )
308 {
309  SCIP_COL* col1;
310  SCIP_COL* col2;
311  SCIP_ROW** rows1;
312  SCIP_ROW** rows2;
313  int nnonzeros1;
314  int nnonzeros2;
315  int i;
316  int j;
317  int nrows1not2; /* the number of LP-rows of variable 1 which variable 2 doesn't appear in */
318  int nrows2not1; /* vice versa */
319  int nrowmaximum;
320  int nrowabs;
321 
322  assert(var1 != NULL);
323  assert(var2 != NULL);
324 
325  /* get the necessary row and column data */
326  col1 = SCIPvarGetCol(var1);
327  col2 = SCIPvarGetCol(var2);
328  rows1 = SCIPcolGetRows(col1);
329  rows2 = SCIPcolGetRows(col2);
330  nnonzeros1 = SCIPcolGetNNonz(col1);
331  nnonzeros2 = SCIPcolGetNNonz(col2);
332 
333  assert(nnonzeros1 == 0 || rows1 != NULL);
334  assert(nnonzeros2 == 0 || rows2 != NULL);
335 
336  if( nnonzeros1 == 0 && nnonzeros2 == 0 )
337  return TRUE;
338 
339  /* if matching rate is 0.0, we don't need to check anything */
340  if( matchingrate == 0.0 )
341  return TRUE;
342 
343  /* initialize the counters for the number of rows not shared. */
344  nrowmaximum = MAX(nnonzeros1, nnonzeros2);
345 
346  nrowabs = ABS(nnonzeros1 - nnonzeros2);
347  nrows1not2 = nrowmaximum - nnonzeros2;
348  nrows2not1 = nrowmaximum - nnonzeros1;
349 
350  /* if the numbers of nonzero rows differs too much, w.r.t.matching ratio, the more expensive check over the rows
351  * doesn't have to be applied anymore because the counters for not shared rows can only increase.
352  */
353  assert(nrowmaximum > 0);
354 
355  if( (nrowmaximum - nrowabs) / (SCIP_Real) nrowmaximum < matchingrate )
356  return FALSE;
357 
358  i = 0;
359  j = 0;
360 
361  /* loop over all rows and determine number of non-shared rows */
362  while( i < nnonzeros1 && j < nnonzeros2 )
363  {
364  /* variables share a common row */
365  if( SCIProwGetIndex(rows1[i]) == SCIProwGetIndex(rows2[j]) )
366  {
367  ++i;
368  ++j;
369  }
370  /* variable 1 appears in rows1[i], variable 2 doesn't */
371  else if( SCIProwGetIndex(rows1[i]) < SCIProwGetIndex(rows2[j]) )
372  {
373  ++i;
374  ++nrows1not2;
375  }
376  /* variable 2 appears in rows2[j], variable 1 doesn't */
377  else
378  {
379  ++j;
380  ++nrows2not1;
381  }
382  }
383 
384  /* now apply the ratio based comparison, that is if the ratio of shared rows is greater or equal the matching rate
385  * for each variable */
386  /* nnonzeros1 = 0 or nnonzeros2 = 0 iff matching rate is 0, but in this case, we return TRUE at the beginning */
387  /* coverity[divide_by_zero] */
388  return ( SCIPisFeasLE(scip, matchingrate, (nnonzeros1 - nrows1not2) / (SCIP_Real)(nnonzeros1)) ||
389  SCIPisFeasLE(scip, matchingrate, (nnonzeros2 - nrows2not1) / (SCIP_Real)(nnonzeros2)) ); /*lint !e795 */
390 }
391 
392 /** Determines a bound by which the absolute solution value of two integer variables can be shifted at most.
393  *
394  * The criterion is the maintenance of feasibility of any global LP row.
395  * The first implementation only considers shifting proportion 1:1, i.e. if master value is shifted by a certain
396  * integer value k downwards, the value of slave is simultaneously shifted by k upwards.
397  */
398 static
400  SCIP* scip, /**< current scip instance */
401  SCIP_SOL* sol, /**< current incumbent */
402  SCIP_VAR* master, /**< current master variable */
403  DIRECTION masterdirection, /**< the shifting direction of the master variable */
404  SCIP_VAR* slave, /**< slave variable with same LP_row set as master variable */
405  DIRECTION slavedirection, /**< the shifting direction of the slave variable */
406  SCIP_Real* activities, /**< array of LP row activities */
407  int nrows /**< the number of rows in LP and the size of the activities array */
408  )
409 { /*lint --e{715}*/
410  SCIP_Real masterbound;
411  SCIP_Real slavebound;
413 
414  SCIP_COL* col;
415  SCIP_ROW** slaverows;
416  SCIP_ROW** masterrows;
417  SCIP_Real* mastercolvals;
418  SCIP_Real* slavecolvals;
419  int nslaverows;
420  int nmasterrows;
421  int i;
422  int j;
423 
424  assert(scip != NULL);
425  assert(sol != NULL);
426  assert(master != NULL);
427  assert(slave != NULL);
428  assert(SCIPvarIsIntegral(master) && SCIPvarIsIntegral(slave));
429  assert(masterdirection == DIRECTION_UP || masterdirection == DIRECTION_DOWN);
430  assert(slavedirection == DIRECTION_UP || slavedirection == DIRECTION_DOWN);
431 
432  /* determine the trivial variable bounds for shift */
433  if( masterdirection == DIRECTION_UP )
434  masterbound = SCIPvarGetUbGlobal(master) - SCIPgetSolVal(scip, sol, master);
435  else
436  masterbound = SCIPgetSolVal(scip, sol, master) - SCIPvarGetLbGlobal(master);
437 
438  if( slavedirection == DIRECTION_UP )
439  slavebound = SCIPvarGetUbGlobal(slave) - SCIPgetSolVal(scip, sol, slave);
440  else
441  slavebound = SCIPgetSolVal(scip, sol, slave) - SCIPvarGetLbGlobal(slave);
442 
443  bound = MIN(slavebound, masterbound);
444  assert(!SCIPisInfinity(scip,bound));
445 
446  if( bound < 0.5 )
447  return 0.0;
448 
449  /* get the necessary row and and column data for each variable */
450  col = SCIPvarGetCol(slave);
451  slaverows = SCIPcolGetRows(col);
452  slavecolvals = SCIPcolGetVals(col);
453  nslaverows = SCIPcolGetNNonz(col);
454 
455  col = SCIPvarGetCol(master);
456  mastercolvals = SCIPcolGetVals(col);
457  masterrows = SCIPcolGetRows(col);
458  nmasterrows = SCIPcolGetNNonz(col);
459 
460  assert(nslaverows == 0 || slavecolvals != NULL);
461  assert(nmasterrows == 0 || mastercolvals != NULL);
462 
463  SCIPdebugMsg(scip, " Master: %s with direction %d and %d rows, Slave: %s with direction %d and %d rows \n", SCIPvarGetName(master),
464  (int)masterdirection, nmasterrows, SCIPvarGetName(slave), (int)slavedirection, nslaverows);
465 
466  /* loop over all LP rows and determine the maximum integer bound by which both variables
467  * can be shifted without loss of feasibility
468  */
469  i = 0;
470  j = 0;
471  while( (i < nslaverows || j < nmasterrows) && SCIPisPositive(scip, bound) )
472  {
473  SCIP_ROW* row;
474  SCIP_Real effect;
475  SCIP_Real rhs;
476  SCIP_Real lhs;
477  SCIP_Real activity;
478  int rowpos;
479  int masterindex;
480  int slaveindex;
481  SCIP_Bool slaveincrement;
482  SCIP_Bool masterincrement;
483 
484  /* check if one pointer already reached the end of the respective array */
485  if( i < nslaverows && SCIProwGetLPPos(slaverows[i]) == -1 )
486  {
487  SCIPdebugMsg(scip, " Slaverow %s is not in LP (i=%d, j=%d)\n", SCIProwGetName(slaverows[i]), i, j);
488  i = nslaverows;
489  continue;
490  }
491  if( j < nmasterrows && SCIProwGetLPPos(masterrows[j]) == -1 )
492  {
493  SCIPdebugMsg(scip, " Masterrow %s is not in LP (i=%d, j=%d) \n", SCIProwGetName(masterrows[j]), i, j);
494  j = nmasterrows;
495  continue;
496  }
497 
498  slaveincrement = FALSE;
499  /* If one counter has already reached its limit, assign a huge number to the corresponding
500  * row index to simulate an always greater row position. */
501  if( i < nslaverows )
502  slaveindex = SCIProwGetIndex(slaverows[i]);
503  else
504  slaveindex = INT_MAX;
505 
506  if( j < nmasterrows )
507  masterindex = SCIProwGetIndex(masterrows[j]);
508  else
509  masterindex = INT_MAX;
510 
511  assert(0 <= slaveindex && 0 <= masterindex);
512 
513  assert(slaveindex < INT_MAX || masterindex < INT_MAX);
514 
515  /* the current row is the one with the smaller index */
516  if( slaveindex <= masterindex )
517  {
518  rowpos = SCIProwGetLPPos(slaverows[i]);
519  row = slaverows[i];
520  slaveincrement = TRUE;
521  masterincrement = (slaveindex == masterindex);
522  }
523  else
524  {
525  assert(j < nmasterrows);
526 
527  rowpos = SCIProwGetLPPos(masterrows[j]);
528  row = masterrows[j];
529  masterincrement = TRUE;
530  }
531  assert(row != NULL);
532 
533  /* local rows can be skipped */
534  if( !SCIProwIsLocal(row) )
535  {
536  /* effect is the effect on the row activity by shifting the variables by 1 in the respective directions */
537  effect = 0.0;
538  if( slaveindex <= masterindex )
539  effect += (slavecolvals[i] * (int)slavedirection);
540  if( masterindex <= slaveindex )
541  effect += (mastercolvals[j] * (int)masterdirection);
542 
543  /* get information about the current row */
544  if( rowpos >= 0 && !SCIPisFeasZero(scip, effect) )
545  {
546  /* effect does not equal zero, the bound is determined as minimum positive integer such that
547  * feasibility of this constraint is maintained.
548  * if constraint is an equality constraint, activity and lhs/rhs should be feasibly equal, which
549  * will cause the method to return zero.
550  */
551  assert(rowpos < nrows);
552 
553  activity = activities[rowpos];
554  rhs = SCIProwGetRhs(row);
555  lhs = SCIProwGetLhs(row);
556 
557  /* if the row is an equation, abort because of effect being nonzero */
558  if( SCIPisFeasEQ(scip, lhs, rhs) )
559  return 0.0;
560 
561  assert(SCIPisFeasLE(scip, lhs, activity) && SCIPisFeasLE(scip, activity, rhs));
562 
563  SCIPdebugMsg(scip, " %g <= %g <= %g, bound = %g, effect = %g (%g * %d + %g * %d) (i=%d,j=%d)\n", lhs, activity, rhs, bound, effect,
564  slaveindex <= masterindex ? slavecolvals[i] : 0.0, (int)slavedirection, masterindex <= slaveindex ? mastercolvals[j] : 0.0,
565  (int)masterdirection, i, j);
566 
567  /* if the row has a left hand side, ensure that shifting preserves feasibility of this ">="-constraint */
568  if( !SCIPisInfinity(scip, -lhs) && SCIPisFeasLT(scip, activity + (effect * bound), lhs) )
569  {
570  SCIP_Real newval;
571 
572  assert(SCIPisNegative(scip, effect));
573 
574  newval = SCIPfeasFloor(scip, (lhs - activity)/effect); /*lint !e414*/
575  bound = MIN(bound - 1.0, newval);
576  }
577 
578  /* if the row has an upper bound, ensure that shifting preserves feasibility of this "<="-constraint */
579  if( !SCIPisInfinity(scip, rhs) && SCIPisFeasGT(scip, activity + (effect * bound), rhs) )
580  {
581  SCIP_Real newval;
582 
583  assert(SCIPisPositive(scip, effect));
584 
585  newval = SCIPfeasFloor(scip, (rhs - activity)/effect); /*lint !e414*/
586  bound = MIN(bound - 1.0, newval);
587  }
588 
589  assert(SCIPisFeasLE(scip, lhs, activity + effect * bound) && SCIPisFeasGE(scip, rhs, activity + effect * bound));
590  assert(SCIPisFeasIntegral(scip, bound));
591  }
592  else
593  {
594  SCIPdebugMsg(scip, " Zero effect on row %s, effect %g, master coeff: %g slave coeff: %g (i=%d, j=%d)\n",
595  SCIProwGetName(row), effect, mastercolvals[j], slavecolvals[i], i, j);
596  }
597  }
598  else
599  {
600  SCIPdebugMsg(scip, " Row %s is local.\n", SCIProwGetName(row));
601  }
602 
603  /* increase the counters which belong to the corresponding row. Both counters are increased by
604  * 1 iff rowpos1 <= rowpos2 <= rowpos1 */
605  if( slaveincrement )
606  ++i;
607  if( masterincrement )
608  ++j;
609  }
610 
611  /* due to numerical reasons, bound can be negative. A variable shift by a negative bound is not desired by
612  * by the heuristic -> Change the return value to zero */
613  if( !SCIPisPositive(scip, bound) )
614  bound = 0.0;
615 
616  return bound;
617 }
618 
619 /** Disposes variable with no heuristic relevancy, e.g., due to a fixed solution value, from its neighborhood block.
620  *
621  * The affected neighborhood block is reduced by 1.
622  */
623 static
624 void disposeVariable(
625  SCIP_VAR** vars, /**< problem variables */
626  int* blockend, /**< contains end index of block */
627  int varindex /**< variable index */
628  )
629 {
630  assert(blockend != NULL);
631  assert(varindex <= *blockend);
632 
633  vars[varindex] = vars[*blockend];
634  --(*blockend);
635 }
636 
637 /** realizes the presolve independently from type of variables it's applied to */
638 static
640  SCIP* scip, /**< current scip */
641  SCIP_VAR** vars, /**< problem vars */
642  SCIP_VAR*** varspointer, /**< pointer to heuristic specific variable memory */
643  int nvars, /**< the number of variables */
644  int* nblocks, /**< pointer to store the number of detected blocks */
645  int* maxblocksize, /**< maximum size of a block */
646  int* nblockvars, /**< pointer to store the number of block variables */
647  int** blockstart, /**< pointer to store the array of block start indices */
648  int** blockend, /**< pointer to store the array of block end indices */
649  SCIP_HEUR* heur, /**< the heuristic */
650  SCIP_HEURDATA* heurdata /**< the heuristic data */
651  )
652 {
653  int v;
654  int startindex;
655 
656  assert(scip != NULL);
657  assert(vars != NULL);
658  assert(nvars >= 2);
659  assert(nblocks != NULL);
660  assert(nblockvars != NULL);
661  assert(blockstart != NULL);
662  assert(blockend != NULL);
663  assert(heur != NULL);
664  assert(heurdata != NULL);
665 
666  /* allocate the heuristic specific variables */
667  SCIP_CALL( SCIPduplicateBlockMemoryArray(scip, varspointer, vars, nvars));
668 
669  /* sort the variables with respect to their columns */
670  SCIPsortPtr((void**)(*varspointer), SCIPvarcolComp, nvars);
671 
672  /* start determining blocks, i.e. a set of at least two variables which share most of their row set.
673  * If there is none, heuristic does not need to be executed.
674  */
675  startindex = 0;
676  *nblocks = 0;
677  *nblockvars = 0;
678 
679  SCIP_CALL( SCIPallocBlockMemoryArray(scip, blockstart, nvars/2) );
680  SCIP_CALL( SCIPallocBlockMemoryArray(scip, blockend, nvars/2) );
681 
682  /* loop over variables and compare neighbors */
683  for( v = 1; v < nvars; ++v )
684  {
685  if( !checkConstraintMatching(scip, (*varspointer)[startindex], (*varspointer)[v], heurdata->matchingrate) )
686  {
687  /* current block has its last variable at position v-1. If v differs from startindex by at least 2,
688  * a block is detected. Update the data correspondingly */
689  if( v - startindex >= 2 )
690  {
691  assert(*nblocks < nvars/2);
692  (*nblockvars) += v - startindex;
693  (*maxblocksize) = MAX((*maxblocksize), v - startindex);
694  (*blockstart)[*nblocks] = startindex;
695  (*blockend)[*nblocks] = v - 1;
696  (*nblocks)++;
697  }
698  startindex = v;
699  }
700  else if( v == nvars - 1 && v - startindex >= 1 )
701  {
702  assert(*nblocks < nvars/2);
703  (*nblockvars) += v - startindex + 1;
704  (*maxblocksize) = MAX((*maxblocksize), v - startindex + 1);
705  (*blockstart)[*nblocks] = startindex;
706  (*blockend)[*nblocks] = v;
707  (*nblocks)++;
708  }
709  }
710 
711  /* reallocate memory with respect to the number of found blocks; if there were none, free the memory */
712  if( *nblocks > 0 )
713  {
714  SCIP_CALL( SCIPreallocBlockMemoryArray(scip, blockstart, nvars/2, *nblocks) );
715  SCIP_CALL( SCIPreallocBlockMemoryArray(scip, blockend, nvars/2, *nblocks) );
716  }
717  else
718  {
719  SCIPfreeBlockMemoryArray(scip, blockstart, nvars/2);
720  SCIPfreeBlockMemoryArray(scip, blockend, nvars/2);
721 
722  *blockstart = NULL;
723  *blockend = NULL;
724  }
725 
726  return SCIP_OKAY;
727 }
728 
729 /** initializes the required structures for execution of heuristic.
730  *
731  * If objective coefficient functions are not all equal, each Binary and Integer variables are sorted
732  * into heuristic-specific arrays with respect to their lexicographical column order,
733  * where every zero in a column is interpreted as zero and every nonzero as '1'.
734  * After the sorting, the variables are compared with respect to user parameter matchingrate and
735  * the heuristic specific blocks are determined.
736  */
737 static
739  SCIP* scip, /**< current scip instance */
740  SCIP_HEUR* heur, /**< heuristic */
741  SCIP_HEURDATA* heurdata /**< the heuristic data */
742  )
743 {
744  int nbinvars;
745  int nintvars;
746  int nvars;
747  SCIP_VAR** vars;
748  int nbinblockvars = 0;
749  int nintblockvars;
750  int maxbinblocksize = 0;
751  int maxintblocksize;
752 
753  assert(scip != NULL);
754  assert(heurdata != NULL);
755 
756  /* ensure that method is not executed if presolving was already applied once in current branch and bound process */
757  if( heurdata->presolved )
758  return SCIP_OKAY;
759 
760  /* get necessary variable information, i.e. number of binary and integer variables */
761  SCIP_CALL( SCIPgetVarsData(scip, &vars, &nvars, &nbinvars, &nintvars, NULL, NULL) );
762 
763  /* if number of binary problem variables exceeds 2, they are subject to 2-optimization algorithm, hence heuristic
764  * calls innerPresolve method to detect necessary structures. */
765  if( nbinvars >= 2 )
766  {
767  SCIP_CALL( innerPresolve(scip, vars, &(heurdata->binvars), nbinvars, &(heurdata->nbinblocks), &maxbinblocksize,
768  &nbinblockvars, &(heurdata->binblockstart), &(heurdata->binblockend), heur, heurdata) );
769  }
770 
771  heurdata->nbinvars = nbinvars;
772  heurdata->execute = nbinvars > 1 && heurdata->nbinblocks > 0;
773 
774 #ifdef SCIP_STATISTIC
775  /* update statistics */
776  heurdata->binnblocks += (heurdata->nbinblocks);
777  heurdata->binnblockvars += nbinblockvars;
778  heurdata->ntotalbinvars += nbinvars;
779  heurdata->maxbinblocksize = MAX(maxbinblocksize, heurdata->maxbinblocksize);
780 
781  SCIPstatisticMessage(" Twoopt BINARY presolving finished with <%d> blocks, <%d> block variables \n",
782  heurdata->nbinblocks, nbinblockvars);
783 #endif
784 
785  if( heurdata->intopt && nintvars > 1 )
786  {
787  SCIP_CALL( innerPresolve(scip, &(vars[nbinvars]), &(heurdata->intvars), nintvars, &(heurdata->nintblocks), &maxintblocksize,
788  &nintblockvars, &(heurdata->intblockstart), &(heurdata->intblockend),
789  heur, heurdata) );
790 
791  heurdata->execute = heurdata->execute || heurdata->nintblocks > 0;
792 
793 #ifdef SCIP_STATISTIC
794  /* update statistics */
795  heurdata->intnblocks += heurdata->nintblocks;
796  heurdata->intnblockvars += nintblockvars;
797  heurdata->ntotalintvars += nintvars;
798  heurdata->maxintblocksize = MAX(maxintblocksize, heurdata->maxintblocksize);
799  SCIPstatisticMessage(" Twoopt Integer presolving finished with <%d> blocks, <%d> block variables \n",
800  heurdata->nintblocks, nintblockvars);
801  SCIPstatisticMessage(" INTEGER coefficients are all equal \n");
802 #endif
803  }
804  heurdata->nintvars = nintvars;
805 
806  /* presolving is finished, heuristic data is updated*/
807  heurdata->presolved = TRUE;
808  SCIPheurSetData(heur, heurdata);
809 
810  return SCIP_OKAY;
811 }
812 
813 /*
814  * Callback methods of primal heuristic
815  */
816 
817 /** copy method for primal heuristic plugins (called when SCIP copies plugins) */
818 static
819 SCIP_DECL_HEURCOPY(heurCopyTwoopt)
820 { /*lint --e{715}*/
821  assert(scip != NULL);
822  assert(heur != NULL);
823  assert(strcmp(SCIPheurGetName(heur), HEUR_NAME) == 0);
824 
825  /* call inclusion method of primal heuristic */
827 
828  return SCIP_OKAY;
829 }
830 
831 /** destructor of primal heuristic to free user data (called when SCIP is exiting) */
832 static
833 SCIP_DECL_HEURFREE(heurFreeTwoopt)
834 { /*lint --e{715}*/
835  SCIP_HEURDATA* heurdata;
836 
837  assert(heur != NULL);
838  assert(strcmp(SCIPheurGetName(heur), HEUR_NAME) == 0);
839  assert(scip != NULL);
840 
841  /* free heuristic data */
842  heurdata = SCIPheurGetData(heur);
843  assert(heurdata != NULL);
844 
845  SCIPfreeBlockMemory(scip, &heurdata);
846  SCIPheurSetData(heur, NULL);
847 
848  return SCIP_OKAY;
849 }
850 
851 /** initialization method of primal heuristic (called after problem was transformed) */
852 static
853 SCIP_DECL_HEURINIT(heurInitTwoopt)
854 {
855  SCIP_HEURDATA* heurdata;
856  assert(heur != NULL);
857  assert(strcmp(SCIPheurGetName(heur), HEUR_NAME) == 0);
858  assert(scip != NULL);
859 
860  heurdata = SCIPheurGetData(heur);
861  assert(heurdata != NULL);
862 
863  /* heuristic has not run yet, all heuristic specific data is set to initial values */
864  heurdata->nbinvars = 0;
865  heurdata->nintvars = 0;
866  heurdata->lastsolindex = -1;
867  heurdata->presolved = FALSE;
868  heurdata->nbinblocks = 0;
869  heurdata->nintblocks = 0;
870 
871  /* create random number generator */
872  SCIP_CALL( SCIPcreateRandom(scip, &heurdata->randnumgen,
874 
875 #ifdef SCIP_STATISTIC
876  /* initialize statistics */
877  heurdata->binnexchanges = 0;
878  heurdata->intnexchanges = 0;
879  heurdata->binnblockvars = 0;
880  heurdata->intnblockvars = 0;
881  heurdata->binnblocks = 0;
882  heurdata->intnblocks = 0;
883 
884  heurdata->maxbinblocksize = 0;
885  heurdata->maxintblocksize = 0;
886 
887  heurdata->ntotalbinvars = 0;
888  heurdata->ntotalintvars = 0;
889  heurdata->nruns = 0;
890 #endif
891 
892  /* all pointers are initially set to NULL. Since presolving
893  * of the heuristic requires a lot of calculation time on some instances,
894  * but might not be needed e.g. if problem is infeasible, presolving is applied
895  * when heuristic is executed for the first time
896  */
897  heurdata->binvars = NULL;
898  heurdata->intvars = NULL;
899  heurdata->binblockstart = NULL;
900  heurdata->binblockend = NULL;
901  heurdata->intblockstart = NULL;
902  heurdata->intblockend = NULL;
903 
904  SCIPheurSetData(heur, heurdata);
905 
906  return SCIP_OKAY;
907 }
908 
909 /* Realizes the 2-optimization algorithm, which tries to improve incumbent solution
910  * by shifting pairs of variables which share a common row set.
911  */
912 static
914  SCIP* scip, /**< current SCIP instance */
915  SCIP_SOL* worksol, /**< working solution */
916  SCIP_VAR** vars, /**< binary or integer variables */
917  int* blockstart, /**< contains start indices of blocks */
918  int* blockend, /**< contains end indices of blocks */
919  int nblocks, /**< the number of blocks */
920  OPTTYPE opttype, /**< are binaries or integers optimized */
921  SCIP_Real* activities, /**< the LP-row activities */
922  int nrows, /**< the number of LP rows */
923  SCIP_Bool* improvement, /**< was there a successful shift? */
924  SCIP_Bool* varboundserr, /**< has the current incumbent already been cut off */
925  SCIP_HEURDATA* heurdata /**< the heuristic data */
926  )
927 { /*lint --e{715}*/
928  int b;
929  SCIP_Real* objchanges;
930  SCIP_VAR** bestmasters;
931  SCIP_VAR** bestslaves;
932  int* bestdirections;
933  int arraysize;
934  int npairs = 0;
935 
936  assert(scip != NULL);
937  assert(nblocks > 0);
938  assert(blockstart != NULL && blockend != NULL);
939  assert(varboundserr != NULL);
940  assert(activities != NULL);
941  assert(worksol != NULL);
942  assert(improvement != NULL);
943 
944  *varboundserr = FALSE;
945 
946  SCIP_CALL( SCIPallocBufferArray(scip, &bestmasters, DEFAULT_ARRAYSIZE) );
947  SCIP_CALL( SCIPallocBufferArray(scip, &bestslaves, DEFAULT_ARRAYSIZE) );
948  SCIP_CALL( SCIPallocBufferArray(scip, &objchanges, DEFAULT_ARRAYSIZE) );
949  SCIP_CALL( SCIPallocBufferArray(scip, &bestdirections, DEFAULT_ARRAYSIZE) );
950  arraysize = DEFAULT_ARRAYSIZE;
951 
952  /* iterate over blocks */
953  for( b = 0; b < nblocks; ++b )
954  {
955  int m;
956  int blocklen;
957 
958  blocklen = blockend[b] - blockstart[b] + 1;
959 
960  /* iterate over variables in current block */
961  for( m = 0; m < blocklen; ++m )
962  {
963  /* determine the new master variable for heuristic's optimization method */
964  SCIP_VAR* master;
965  SCIP_Real masterobj;
966  SCIP_Real mastersolval;
967  SCIP_Real bestimprovement;
968  SCIP_Real bestbound;
969  int bestslavepos;
970  int s;
971  int firstslave;
972  int nslaves;
973  int bestdirection;
974  DIRECTION bestmasterdir;
975  DIRECTION bestslavedir;
976 
977  master = vars[blockstart[b] + m]; /*lint !e679*/
978  masterobj = SCIPvarGetObj(master);
979  mastersolval = SCIPgetSolVal(scip, worksol, master);
980 
981  /* due to cuts or fixings of solution values, worksol might not be feasible w.r.t. its bounds.
982  * Exit method in that case. */
983  if( SCIPisFeasGT(scip, mastersolval, SCIPvarGetUbGlobal(master)) || SCIPisFeasLT(scip, mastersolval, SCIPvarGetLbGlobal(master)) )
984  {
985  *varboundserr = TRUE;
986  SCIPdebugMsg(scip, "Solution has violated variable bounds for var %s: %g <= %g <= %g \n",
987  SCIPvarGetName(master), SCIPvarGetLbGlobal(master), mastersolval, SCIPvarGetUbGlobal(master));
988  goto TERMINATE;
989  }
990 
991  /* if variable has fixed solution value, it is deleted from heuristic array */
992  if( SCIPisFeasEQ(scip, SCIPvarGetUbGlobal(master), SCIPvarGetLbGlobal(master)) )
993  {
994  disposeVariable(vars, &(blockend[b]), blockstart[b] + m);
995  --blocklen;
996  continue;
997  }
998  else if( SCIPvarGetStatus(master) != SCIP_VARSTATUS_COLUMN )
999  continue;
1000 
1001  assert(SCIPisFeasIntegral(scip, mastersolval));
1002 
1003  assert(opttype == OPTTYPE_INTEGER || (SCIPisFeasLE(scip, mastersolval, 1.0) || SCIPisFeasGE(scip, mastersolval, 0.0)));
1004 
1005  /* initialize the data of the best available shift */
1006  bestimprovement = 0.0;
1007  bestslavepos = -1;
1008  bestbound = 0.0;
1009  bestmasterdir = DIRECTION_NONE;
1010  bestslavedir = DIRECTION_NONE;
1011  bestdirection = -1;
1012 
1013  /* in blocks with more than heurdata->maxnslaves variables, a slave candidate region is chosen */
1014  if( heurdata->maxnslaves >= 0 && blocklen > heurdata->maxnslaves )
1015  firstslave = SCIPrandomGetInt(heurdata->randnumgen, blockstart[b] + m, blockend[b]);
1016  else
1017  firstslave = blockstart[b] + m + 1;
1018 
1019  nslaves = MIN((heurdata->maxnslaves == -1 ? INT_MAX : heurdata->maxnslaves), blocklen);
1020 
1021  /* Loop over block and determine a slave shift candidate for master variable.
1022  * If more than one candidate is available, choose the shift which improves objective function
1023  * the most. */
1024  for( s = 0; s < nslaves; ++s )
1025  {
1026  SCIP_VAR* slave;
1027  SCIP_Real slaveobj;
1028  SCIP_Real slavesolval;
1029  SCIP_Real changedobj;
1030  SCIP_Real diffdirbound;
1031  SCIP_Real equaldirbound;
1032  int directions;
1033  int slaveindex;
1034 
1035  slaveindex = (firstslave + s - blockstart[b]) % blocklen;
1036  slaveindex += blockstart[b];
1037 
1038  /* in case of a small block, we do not want to try possible pairings twice */
1039  if( (blocklen <= heurdata->maxnslaves || heurdata->maxnslaves == -1) && slaveindex < blockstart[b] + m )
1040  break;
1041  /* master and slave should not be the same variable */
1042  if( slaveindex == blockstart[b] + m )
1043  continue;
1044 
1045  /* get the next slave variable */
1046  slave = vars[slaveindex];
1047  slaveobj = SCIPvarGetObj(slave);
1048  slavesolval = SCIPgetSolVal(scip, worksol, slave);
1049  changedobj = 0.0;
1050 
1051  assert(SCIPvarGetType(master) == SCIPvarGetType(slave));
1052  assert(SCIPisFeasIntegral(scip, slavesolval));
1053  assert(opttype == OPTTYPE_INTEGER || (SCIPisFeasLE(scip, mastersolval, 1.0) || SCIPisFeasGE(scip, mastersolval, 0.0)));
1054 
1055  /* solution is not feasible w.r.t. the variable bounds, stop optimization in this case */
1056  if( SCIPisFeasGT(scip, slavesolval, SCIPvarGetUbGlobal(slave)) || SCIPisFeasLT(scip, slavesolval, SCIPvarGetLbGlobal(slave)) )
1057  {
1058  *varboundserr = TRUE;
1059  SCIPdebugMsg(scip, "Solution has violated variable bounds for var %s: %g <= %g <= %g \n",
1060  SCIPvarGetName(slave), SCIPvarGetLbGlobal(slave), slavesolval, SCIPvarGetUbGlobal(slave));
1061  goto TERMINATE;
1062  }
1063 
1064  /* if solution value of the variable is fixed, delete it from the remaining candidates in the block */
1065  if( SCIPisFeasEQ(scip, SCIPvarGetUbGlobal(slave), SCIPvarGetLbGlobal(slave) ) )
1066  {
1067  disposeVariable(vars, &(blockend[b]), slaveindex);
1068  --blocklen;
1069  continue;
1070  }
1071  else if( SCIPvarGetStatus(master) != SCIP_VARSTATUS_COLUMN )
1072  continue;
1073 
1074  /* determine the shifting direction to improve the objective function */
1075  /* assert(SCIPisFeasGT(scip, masterobj, slaveobj)); */
1076 
1077  /* The heuristic chooses the shifting direction and the corresponding maximum nonnegative
1078  * integer shift value for the two variables which preserves feasibility and improves
1079  * the objective function value. */
1080  directions = -1;
1081  diffdirbound = 0.0;
1082  equaldirbound = 0.0;
1083 
1084  if( SCIPisFeasLT(scip, masterobj - slaveobj, 0.0) )
1085  {
1086  diffdirbound = determineBound(scip, worksol, master, DIRECTION_UP, slave, DIRECTION_DOWN, activities, nrows);
1087  directions = 2;
1088  /* the improvement of objective function is calculated */
1089  changedobj = (masterobj - slaveobj) * diffdirbound;
1090  }
1091  else if( SCIPisFeasGT(scip, masterobj - slaveobj, 0.0) )
1092  {
1093  diffdirbound = determineBound(scip, worksol, master, DIRECTION_DOWN, slave, DIRECTION_UP, activities, nrows);
1094  directions = 1;
1095  changedobj = (slaveobj - masterobj) * diffdirbound;
1096  }
1097 
1098  if( SCIPisFeasLT(scip, masterobj + slaveobj, 0.0) )
1099  {
1100  equaldirbound = determineBound(scip, worksol, master, DIRECTION_UP, slave, DIRECTION_UP, activities, nrows);
1101  if( SCIPisFeasLT(scip, (slaveobj + masterobj) * equaldirbound, changedobj) )
1102  {
1103  changedobj = (slaveobj + masterobj) * equaldirbound;
1104  directions = 3;
1105  }
1106  }
1107  else if( SCIPisFeasGT(scip, masterobj + slaveobj, 0.0) )
1108  {
1109  equaldirbound = determineBound(scip, worksol, master, DIRECTION_DOWN, slave, DIRECTION_DOWN, activities, nrows);
1110  if( SCIPisFeasLT(scip, -(slaveobj + masterobj) * equaldirbound, changedobj) )
1111  {
1112  changedobj = -(slaveobj + masterobj) * equaldirbound;
1113  directions = 0;
1114  }
1115  }
1116  assert(SCIPisFeasIntegral(scip, equaldirbound));
1117  assert(SCIPisFeasIntegral(scip, diffdirbound));
1118  assert(SCIPisFeasGE(scip, equaldirbound, 0.0));
1119  assert(SCIPisFeasGE(scip, diffdirbound, 0.0));
1120 
1121  /* choose the candidate which improves the objective function the most */
1122  if( (SCIPisFeasGT(scip, equaldirbound, 0.0) || SCIPisFeasGT(scip, diffdirbound, 0.0))
1123  && SCIPisFeasLT(scip, changedobj, bestimprovement) )
1124  {
1125  bestimprovement = changedobj;
1126  bestslavepos = slaveindex;
1127  bestdirection = directions;
1128 
1129  /* the most promising shift, i.e., the one which can improve the objective
1130  * the most, is recorded by the integer 'directions'. It is recovered via the use
1131  * of a binary representation of the four different combinations for the shifting directions
1132  * of two variables */
1133  if( directions / 2 == 1 )
1134  bestmasterdir = DIRECTION_UP;
1135  else
1136  bestmasterdir = DIRECTION_DOWN;
1137 
1138  if( directions % 2 == 1 )
1139  bestslavedir = DIRECTION_UP;
1140  else
1141  bestslavedir = DIRECTION_DOWN;
1142 
1143  if( bestmasterdir == bestslavedir )
1144  bestbound = equaldirbound;
1145  else
1146  bestbound = diffdirbound;
1147  }
1148  }
1149 
1150  /* choose the most promising candidate, if one exists */
1151  if( bestslavepos >= 0 )
1152  {
1153  if( npairs == arraysize )
1154  {
1155  SCIP_CALL( SCIPreallocBufferArray(scip, &bestmasters, 2 * arraysize) );
1156  SCIP_CALL( SCIPreallocBufferArray(scip, &bestslaves, 2 * arraysize) );
1157  SCIP_CALL( SCIPreallocBufferArray(scip, &objchanges, 2 * arraysize) );
1158  SCIP_CALL( SCIPreallocBufferArray(scip, &bestdirections, 2 * arraysize) );
1159  arraysize = 2 * arraysize;
1160  }
1161  assert( npairs < arraysize );
1162 
1163  bestmasters[npairs] = master;
1164  bestslaves[npairs] = vars[bestslavepos];
1165  objchanges[npairs] = ((int)bestslavedir * SCIPvarGetObj(bestslaves[npairs]) + (int)bestmasterdir * masterobj) * bestbound;
1166  bestdirections[npairs] = bestdirection;
1167 
1168  assert(objchanges[npairs] < 0);
1169 
1170  SCIPdebugMsg(scip, " Saved candidate pair {%s=%g, %s=%g} with objectives <%g>, <%g> to be set to {%g, %g} %d\n",
1171  SCIPvarGetName(master), mastersolval, SCIPvarGetName(bestslaves[npairs]), SCIPgetSolVal(scip, worksol, bestslaves[npairs]) ,
1172  masterobj, SCIPvarGetObj(bestslaves[npairs]), mastersolval + (int)bestmasterdir * bestbound, SCIPgetSolVal(scip, worksol, bestslaves[npairs])
1173  + (int)bestslavedir * bestbound, bestdirections[npairs]);
1174 
1175  ++npairs;
1176  }
1177  }
1178  }
1179 
1180  if( npairs == 0 )
1181  goto TERMINATE;
1182 
1183  SCIPsortRealPtrPtrInt(objchanges, (void**)bestmasters, (void**)bestslaves, bestdirections, npairs);
1184 
1185  for( b = 0; b < npairs; ++b )
1186  {
1187  SCIP_VAR* master;
1188  SCIP_VAR* slave;
1189  SCIP_Real mastersolval;
1190  SCIP_Real slavesolval;
1191  SCIP_Real masterobj;
1192  SCIP_Real slaveobj;
1193  SCIP_Real bound;
1194  DIRECTION masterdir;
1195  DIRECTION slavedir;
1196 
1197  master = bestmasters[b];
1198  slave = bestslaves[b];
1199  mastersolval = SCIPgetSolVal(scip, worksol, master);
1200  slavesolval = SCIPgetSolVal(scip, worksol, slave);
1201  masterobj =SCIPvarGetObj(master);
1202  slaveobj = SCIPvarGetObj(slave);
1203 
1204  assert(0 <= bestdirections[b] && bestdirections[b] < 4);
1205 
1206  if( bestdirections[b] / 2 == 1 )
1207  masterdir = DIRECTION_UP;
1208  else
1209  masterdir = DIRECTION_DOWN;
1210 
1211  if( bestdirections[b] % 2 == 1 )
1212  slavedir = DIRECTION_UP;
1213  else
1214  slavedir = DIRECTION_DOWN;
1215 
1216  bound = determineBound(scip, worksol, master, masterdir, slave, slavedir, activities, nrows);
1217 
1218  if( !SCIPisZero(scip, bound) )
1219  {
1220  SCIP_Bool feasible;
1221 #ifndef NDEBUG
1222  SCIP_Real changedobj;
1223 #endif
1224 
1225  SCIPdebugMsg(scip, " Promising candidates {%s=%g, %s=%g} with objectives <%g>, <%g> to be set to {%g, %g}\n",
1226  SCIPvarGetName(master), mastersolval, SCIPvarGetName(slave), slavesolval,
1227  masterobj, slaveobj, mastersolval + (int)masterdir * bound, slavesolval + (int)slavedir * bound);
1228 
1229 #ifndef NDEBUG
1230  /* the improvement of objective function is calculated */
1231  changedobj = ((int)slavedir * slaveobj + (int)masterdir * masterobj) * bound;
1232  assert(SCIPisFeasLT(scip, changedobj, 0.0));
1233 #endif
1234 
1236  /* try to change the solution values of the variables */
1237  feasible = FALSE;
1238  SCIP_CALL( shiftValues(scip, master, slave, mastersolval, masterdir, slavesolval, slavedir, bound,
1239  activities, nrows, &feasible) );
1240 
1241  if( feasible )
1242  {
1243  /* The variables' solution values were successfully shifted and can hence be updated. */
1244  assert(SCIPisFeasIntegral(scip, mastersolval + ((int)masterdir * bound)));
1245  assert(SCIPisFeasIntegral(scip, slavesolval + ((int)slavedir * bound)));
1246 
1247  SCIP_CALL( SCIPsetSolVal(scip, worksol, master, mastersolval + (int)masterdir * bound) );
1248  SCIP_CALL( SCIPsetSolVal(scip, worksol, slave, slavesolval + (int)slavedir * bound) );
1249  SCIPdebugMsg(scip, " Feasible shift: <%s>[%g, %g] (obj: %f) <%f> --> <%f>\n",
1250  SCIPvarGetName(master), SCIPvarGetLbGlobal(master), SCIPvarGetUbGlobal(master), masterobj, mastersolval, SCIPgetSolVal(scip, worksol, master));
1251  SCIPdebugMsg(scip, " <%s>[%g, %g] (obj: %f) <%f> --> <%f>\n",
1252  SCIPvarGetName(slave), SCIPvarGetLbGlobal(slave), SCIPvarGetUbGlobal(slave), slaveobj, slavesolval, SCIPgetSolVal(scip, worksol, slave));
1253 
1254 #ifdef SCIP_STATISTIC
1255  /* update statistics */
1256  if( opttype == OPTTYPE_BINARY )
1257  ++(heurdata->binnexchanges);
1258  else
1259  ++(heurdata->intnexchanges);
1260 #endif
1261 
1262  *improvement = TRUE;
1263  }
1264  }
1265  }
1266  TERMINATE:
1267  SCIPfreeBufferArray(scip, &bestdirections);
1268  SCIPfreeBufferArray(scip, &objchanges);
1269  SCIPfreeBufferArray(scip, &bestslaves);
1270  SCIPfreeBufferArray(scip, &bestmasters);
1271 
1272  return SCIP_OKAY;
1273 }
1274 
1275 /** deinitialization method of primal heuristic (called before transformed problem is freed) */
1276 static
1277 SCIP_DECL_HEUREXIT(heurExitTwoopt)
1279  SCIP_HEURDATA* heurdata;
1280 
1281  heurdata = SCIPheurGetData(heur);
1282  assert(heurdata != NULL);
1283 
1284  /*ensure that initialization was successful */
1285  assert(heurdata->nbinvars <= 1 || heurdata->binvars != NULL);
1286 
1287 #ifdef SCIP_STATISTIC
1288  /* print relevant statistics to console */
1290  " Twoopt Binary Statistics : "
1291  "%6.2g %6.2g %4.2g %4.0g %6d (blocks/run, variables/run, varpercentage, avg. block size, max block size) \n",
1292  heurdata->nruns == 0 ? 0.0 : (SCIP_Real)heurdata->binnblocks/(heurdata->nruns),
1293  heurdata->nruns == 0 ? 0.0 : (SCIP_Real)heurdata->binnblockvars/(heurdata->nruns),
1294  heurdata->ntotalbinvars == 0 ? 0.0 : (SCIP_Real)heurdata->binnblockvars/(heurdata->ntotalbinvars) * 100.0,
1295  heurdata->binnblocks == 0 ? 0.0 : heurdata->binnblockvars/(SCIP_Real)(heurdata->binnblocks),
1296  heurdata->maxbinblocksize);
1297 
1299  " Twoopt Integer statistics : "
1300  "%6.2g %6.2g %4.2g %4.0g %6d (blocks/run, variables/run, varpercentage, avg block size, max block size) \n",
1301  heurdata->nruns == 0 ? 0.0 : (SCIP_Real)heurdata->intnblocks/(heurdata->nruns),
1302  heurdata->nruns == 0 ? 0.0 : (SCIP_Real)heurdata->intnblockvars/(heurdata->nruns),
1303  heurdata->ntotalintvars == 0 ? 0.0 : (SCIP_Real)heurdata->intnblockvars/(heurdata->ntotalintvars) * 100.0,
1304  heurdata->intnblocks == 0 ? 0.0 : heurdata->intnblockvars/(SCIP_Real)(heurdata->intnblocks),
1305  heurdata->maxintblocksize);
1306 
1308  " Twoopt results : "
1309  "%6d %6d %4d %4.2g (runs, binary exchanges, Integer shiftings, matching rate)\n",
1310  heurdata->nruns,
1311  heurdata->binnexchanges,
1312  heurdata->intnexchanges,
1313  heurdata->matchingrate);
1314 
1315  /* set statistics to initial values*/
1316  heurdata->binnblockvars = 0;
1317  heurdata->binnblocks = 0;
1318  heurdata->intnblocks = 0;
1319  heurdata->intnblockvars = 0;
1320  heurdata->binnexchanges = 0;
1321  heurdata->intnexchanges = 0;
1322 #endif
1323 
1324  /* free the allocated memory for the binary variables */
1325  if( heurdata->binvars != NULL )
1326  {
1327  SCIPfreeBlockMemoryArray(scip, &heurdata->binvars, heurdata->nbinvars);
1328  }
1329 
1330  if( heurdata->nbinblocks > 0 )
1331  {
1332  assert(heurdata->binblockstart != NULL);
1333  assert(heurdata->binblockend != NULL);
1334 
1335  SCIPfreeBlockMemoryArray(scip, &heurdata->binblockstart, heurdata->nbinblocks);
1336  SCIPfreeBlockMemoryArray(scip, &heurdata->binblockend, heurdata->nbinblocks);
1337  }
1338  heurdata->nbinvars = 0;
1339  heurdata->nbinblocks = 0;
1340 
1341  if( heurdata->nintblocks > 0 )
1342  {
1343  assert(heurdata->intblockstart != NULL);
1344  assert(heurdata->intblockend != NULL);
1345 
1346  SCIPfreeBlockMemoryArray(scip, &heurdata->intblockstart, heurdata->nintblocks);
1347  SCIPfreeBlockMemoryArray(scip, &heurdata->intblockend, heurdata->nintblocks);
1348  }
1349 
1350  /* free the allocated memory for the integers */
1351  if( heurdata->intvars != NULL )
1352  {
1353  SCIPfreeBlockMemoryArray(scip, &heurdata->intvars, heurdata->nintvars);
1354  }
1355 
1356  heurdata->nbinblocks = 0;
1357  heurdata->nintblocks = 0;
1358  heurdata->nbinvars = 0;
1359  heurdata->nintvars = 0;
1360 
1361  assert(heurdata->binvars == NULL);
1362  assert(heurdata->intvars == NULL);
1363 
1364  /* free random number generator */
1365  SCIPfreeRandom(scip, &heurdata->randnumgen);
1366 
1367  SCIPheurSetData(heur, heurdata);
1368 
1369  return SCIP_OKAY;
1370 }
1371 
1372 /** solving process initialization method of primal heuristic (called when branch and bound process is about to begin) */
1373 static
1374 SCIP_DECL_HEURINITSOL(heurInitsolTwoopt)
1376  SCIP_HEURDATA* heurdata;
1377  assert(heur != NULL);
1378  assert(strcmp(SCIPheurGetName(heur), HEUR_NAME) == 0);
1379  assert(scip != NULL);
1380 
1381  /* get heuristic data */
1382  heurdata = SCIPheurGetData(heur);
1383 
1384  assert(heurdata != NULL);
1385  assert(heurdata->binvars == NULL && heurdata->intvars == NULL);
1386  assert(heurdata->binblockstart == NULL && heurdata->binblockend == NULL);
1387  assert(heurdata->intblockstart == NULL && heurdata->intblockend == NULL);
1388 
1389  /* set heuristic data to initial values, but increase the total number of runs */
1390  heurdata->nbinvars = 0;
1391  heurdata->nintvars = 0;
1392  heurdata->lastsolindex = -1;
1393  heurdata->presolved = FALSE;
1394 
1395 #ifdef SCIP_STATISTIC
1396  ++(heurdata->nruns);
1397 #endif
1398 
1399  SCIPheurSetData(heur, heurdata);
1400 
1401  return SCIP_OKAY;
1402 }
1403 
1404 
1405 /** solving process deinitialization method of primal heuristic (called before branch and bound process data is freed) */
1406 static
1407 SCIP_DECL_HEUREXITSOL(heurExitsolTwoopt)
1409  SCIP_HEURDATA* heurdata;
1410  int nbinvars;
1411  int nintvars;
1412 
1413  assert(heur != NULL);
1414  assert(scip != NULL);
1415  assert(strcmp(SCIPheurGetName(heur), HEUR_NAME) == 0);
1416  assert(scip != NULL);
1417 
1418  /* get heuristic data */
1419  heurdata = SCIPheurGetData(heur);
1420 
1421  assert(heurdata != NULL);
1422 
1423  nbinvars = heurdata->nbinvars;
1424  nintvars = heurdata->nintvars;
1425 
1426  /* free the allocated memory for the binary variables */
1427  if( heurdata->binvars != NULL )
1428  {
1429  SCIPfreeBlockMemoryArray(scip, &heurdata->binvars, nbinvars);
1430  }
1431  if( heurdata->binblockstart != NULL )
1432  {
1433  assert(heurdata->binblockend != NULL);
1434 
1435  SCIPfreeBlockMemoryArray(scip, &heurdata->binblockstart, heurdata->nbinblocks);
1436  SCIPfreeBlockMemoryArray(scip, &heurdata->binblockend, heurdata->nbinblocks);
1437  }
1438  heurdata->nbinvars = 0;
1439  heurdata->nbinblocks = 0;
1440 
1441  if( heurdata->intblockstart != NULL )
1442  {
1443  assert(heurdata->intblockend != NULL);
1444 
1445  SCIPfreeBlockMemoryArray(scip, &heurdata->intblockstart, heurdata->nintblocks);
1446  SCIPfreeBlockMemoryArray(scip, &heurdata->intblockend, heurdata->nintblocks);
1447  }
1448  heurdata->nintblocks = 0;
1449 
1450  /* free the allocated memory for the integers */
1451  if( heurdata->intvars != NULL )
1452  {
1453  SCIPfreeBlockMemoryArray(scip, &heurdata->intvars, nintvars);
1454  }
1455 
1456  heurdata->nintvars = 0;
1457 
1458  assert(heurdata->binvars == NULL && heurdata->intvars == NULL);
1459  assert(heurdata->binblockstart == NULL && heurdata->binblockend == NULL);
1460  assert(heurdata->intblockstart == NULL && heurdata->intblockend == NULL);
1461 
1462  /* set heuristic data */
1463  SCIPheurSetData(heur, heurdata);
1464 
1465  return SCIP_OKAY;
1466 }
1467 
1468 /** execution method of primal heuristic */
1469 static
1470 SCIP_DECL_HEUREXEC(heurExecTwoopt)
1471 { /*lint --e{715}*/
1472  SCIP_HEURDATA* heurdata;
1473  SCIP_SOL* bestsol;
1474  SCIP_SOL* worksol;
1475  SCIP_ROW** lprows;
1476  SCIP_Real* activities;
1477  SCIP_COL** cols;
1478  int ncols;
1479  int nbinvars;
1480  int nintvars;
1481  int ndiscvars;
1482  int nlprows;
1483  int i;
1484  int ncolsforsorting;
1485  SCIP_Bool improvement;
1486  SCIP_Bool presolthiscall;
1487  SCIP_Bool varboundserr;
1488 
1489  assert(heur != NULL);
1490  assert(scip != NULL);
1491  assert(result != NULL);
1492 
1493  /* get heuristic data */
1494  heurdata = SCIPheurGetData(heur);
1495  assert(heurdata != NULL);
1496 
1497  *result = SCIP_DIDNOTRUN;
1498 
1499  /* we need an LP */
1500  if( SCIPgetNLPRows(scip) == 0 )
1501  return SCIP_OKAY;
1502 
1503  bestsol = SCIPgetBestSol(scip);
1504 
1505  /* ensure that heuristic has not already been processed on current incumbent */
1506  if( bestsol == NULL || heurdata->lastsolindex == SCIPsolGetIndex(bestsol) )
1507  return SCIP_OKAY;
1508 
1509  heurdata->lastsolindex = SCIPsolGetIndex(bestsol);
1510 
1511  /* we can only work on solutions valid in the transformed space */
1512  if( SCIPsolIsOriginal(bestsol) )
1513  return SCIP_OKAY;
1514 
1515 #ifdef SCIP_DEBUG
1516  SCIP_CALL( SCIPprintSol(scip, bestsol, NULL, TRUE) );
1517 #endif
1518 
1519  /* ensure that the user defined number of nodes after last best solution has been reached, return otherwise */
1520  if( (SCIPgetNNodes(scip) - SCIPsolGetNodenum(bestsol)) < heurdata->waitingnodes )
1521  return SCIP_OKAY;
1522 
1523  presolthiscall = FALSE;
1524  SCIP_CALL( SCIPgetLPColsData(scip,&cols, &ncols) );
1525  ndiscvars = SCIPgetNBinVars(scip) + SCIPgetNIntVars(scip);
1526  ncolsforsorting = MIN(ncols, ndiscvars);
1527 
1528  /* ensure that heuristic specific presolve is applied when heuristic is executed first */
1529  if( !heurdata->presolved )
1530  {
1531  SCIP_CALL( SCIPgetLPColsData(scip,&cols, &ncols) );
1532 
1533  for( i = 0; i < ncolsforsorting; ++i )
1534  SCIPcolSort(cols[i]);
1535 
1536  SCIP_CALL( presolveTwoOpt(scip, heur, heurdata) );
1537  presolthiscall = TRUE;
1538  }
1539 
1540  assert(heurdata->presolved);
1541 
1542  SCIPdebugMsg(scip, " Twoopt heuristic is %sexecuting.\n", heurdata->execute ? "" : "not ");
1543  /* ensure that presolve has detected structures in the problem to which the 2-optimization can be applied.
1544  * That is if variables exist which share a common set of LP-rows. */
1545  if( !heurdata->execute )
1546  return SCIP_OKAY;
1547 
1548  nbinvars = heurdata->nbinvars;
1549  nintvars = heurdata->nintvars;
1550  ndiscvars = nbinvars + nintvars;
1551 
1552  /* we need to be able to start diving from current node in order to resolve the LP
1553  * with continuous or implicit integer variables
1554  */
1555  if( SCIPgetNVars(scip) > ndiscvars && ( !SCIPhasCurrentNodeLP(scip) || SCIPgetLPSolstat(scip) != SCIP_LPSOLSTAT_OPTIMAL ) )
1556  return SCIP_OKAY;
1557 
1558  /* problem satisfies all necessary conditions for 2-optimization heuristic, execute heuristic! */
1559  *result = SCIP_DIDNOTFIND;
1560 
1561  /* initialize a working solution as a copy of the current incumbent to be able to store
1562  * possible improvements obtained by 2-optimization */
1563  SCIP_CALL( SCIPcreateSolCopy(scip, &worksol, bestsol) );
1564  SCIPsolSetHeur(worksol, heur);
1565 
1566  /* get the LP row activities from current incumbent bestsol */
1567  SCIP_CALL( SCIPgetLPRowsData(scip, &lprows, &nlprows) );
1568  SCIP_CALL( SCIPallocBufferArray(scip, &activities, nlprows) );
1569 
1570  for( i = 0; i < nlprows; i++ )
1571  {
1572  SCIP_ROW* row;
1573 
1574  row = lprows[i];
1575  assert(row != NULL);
1576  assert(SCIProwGetLPPos(row) == i);
1577  SCIPdebugMsg(scip, " Row <%d> is %sin LP: \n", i, SCIProwGetLPPos(row) >= 0 ? "" : "not ");
1578  SCIPdebug( SCIP_CALL( SCIPprintRow(scip, row, NULL) ) );
1579  activities[i] = SCIPgetRowSolActivity(scip, row, bestsol);
1580 
1581  /* Heuristic does not provide infeasibility recovery, thus if any constraint is violated,
1582  * execution has to be terminated.
1583  */
1584  if( !SCIProwIsLocal(row) && (SCIPisFeasLT(scip, activities[i], SCIProwGetLhs(row))
1585  || SCIPisFeasGT(scip, activities[i], SCIProwGetRhs(row))) )
1586  goto TERMINATE;
1587  }
1588 
1589  if( !presolthiscall )
1590  {
1591  for( i = 0; i < ncolsforsorting; ++i )
1592  SCIPcolSort(cols[i]);
1593  }
1594  SCIPdebugMsg(scip, " Twoopt heuristic has initialized activities and sorted rows! \n");
1595 
1596  /* start with binary optimization */
1597  improvement = FALSE;
1598  varboundserr = FALSE;
1599 
1600  if( heurdata->nbinblocks > 0 )
1601  {
1602  SCIP_CALL( optimize(scip, worksol, heurdata->binvars, heurdata->binblockstart, heurdata->binblockend, heurdata->nbinblocks,
1603  OPTTYPE_BINARY, activities, nlprows, &improvement, &varboundserr, heurdata) );
1604 
1605  SCIPdebugMsg(scip, " Binary Optimization finished!\n");
1606  }
1607 
1608  if( varboundserr )
1609  goto TERMINATE;
1610 
1611  /* ensure that their are at least two integer variables which do not have the same coefficient
1612  * in the objective function. In one of these cases, the heuristic will automatically skip the
1613  * integer variable optimization */
1614  if( heurdata->nintblocks > 0 )
1615  {
1616  assert(heurdata->intopt);
1617  SCIP_CALL( optimize(scip, worksol, heurdata->intvars, heurdata->intblockstart, heurdata->intblockend, heurdata->nintblocks,
1618  OPTTYPE_INTEGER, activities, nlprows, &improvement, &varboundserr, heurdata) );
1619 
1620  SCIPdebugMsg(scip, " Integer Optimization finished!\n");
1621  }
1622 
1623  if( ! improvement || varboundserr )
1624  goto TERMINATE;
1625 
1626  if( SCIPgetNVars(scip) == ndiscvars )
1627  {
1628  /* the problem is a pure IP, hence, no continuous or implicit variables are left for diving.
1629  * try if new working solution is feasible in original problem */
1630  SCIP_Bool success;
1631 #ifndef NDEBUG
1632  SCIP_CALL( SCIPtrySol(scip, worksol, FALSE, FALSE, TRUE, TRUE, TRUE, &success) );
1633 #else
1634  SCIP_CALL( SCIPtrySol(scip, worksol, FALSE, FALSE, FALSE, FALSE, TRUE, &success) );
1635 #endif
1636 
1637  if( success )
1638  {
1639  SCIPdebugMsg(scip, "found feasible shifted solution:\n");
1640  SCIPdebug( SCIP_CALL( SCIPprintSol(scip, worksol, NULL, FALSE) ) );
1641  heurdata->lastsolindex = SCIPsolGetIndex(bestsol);
1642  *result = SCIP_FOUNDSOL;
1643 
1644 #ifdef SCIP_STATISTIC
1645  SCIPstatisticMessage("***Twoopt improved solution found by %10s . \n",
1646  SCIPsolGetHeur(bestsol) != NULL ? SCIPheurGetName(SCIPsolGetHeur(bestsol)) :"Tree");
1647 #endif
1648  }
1649  }
1650  /* fix the integer variables and start diving to optimize continuous variables with respect to reduced domain */
1651  else
1652  {
1653  SCIP_VAR** allvars;
1654  SCIP_Bool lperror;
1655 #ifdef NDEBUG
1656  SCIP_RETCODE retstat;
1657 #endif
1658 
1659  SCIPdebugMsg(scip, "shifted solution should be feasible -> solve LP to fix continuous variables to best values\n");
1660 
1661  allvars = SCIPgetVars(scip);
1662 
1663 #ifdef SCIP_DEBUG
1664  for( i = ndiscvars; i < SCIPgetNVars(scip); ++i )
1665  {
1666  SCIPdebugMsg(scip, " Cont. variable <%s>, status %d with bounds [%g <= %g <= x <= %g <= %g]\n",
1667  SCIPvarGetName(allvars[i]), SCIPvarGetStatus(allvars[i]), SCIPvarGetLbGlobal(allvars[i]), SCIPvarGetLbLocal(allvars[i]), SCIPvarGetUbLocal(allvars[i]),
1668  SCIPvarGetUbGlobal(allvars[i]));
1669  }
1670 #endif
1671 
1672  /* start diving to calculate the LP relaxation */
1673  SCIP_CALL( SCIPstartDive(scip) );
1674 
1675  /* set the bounds of the variables: fixed for integers, global bounds for continuous */
1676  for( i = 0; i < SCIPgetNVars(scip); ++i )
1677  {
1678  if( SCIPvarGetStatus(allvars[i]) == SCIP_VARSTATUS_COLUMN )
1679  {
1680  SCIP_CALL( SCIPchgVarLbDive(scip, allvars[i], SCIPvarGetLbGlobal(allvars[i])) );
1681  SCIP_CALL( SCIPchgVarUbDive(scip, allvars[i], SCIPvarGetUbGlobal(allvars[i])) );
1682  }
1683  }
1684 
1685  /* apply this after global bounds to not cause an error with intermediate empty domains */
1686  for( i = 0; i < ndiscvars; ++i )
1687  {
1688  if( SCIPvarGetStatus(allvars[i]) == SCIP_VARSTATUS_COLUMN )
1689  {
1690  SCIP_Real solval;
1691 
1692  solval = SCIPgetSolVal(scip, worksol, allvars[i]);
1693 
1694  assert(SCIPvarGetType(allvars[i]) != SCIP_VARTYPE_CONTINUOUS && SCIPisFeasIntegral(scip, solval));
1695 
1696  SCIP_CALL( SCIPchgVarLbDive(scip, allvars[i], solval) );
1697  SCIP_CALL( SCIPchgVarUbDive(scip, allvars[i], solval) );
1698  }
1699  }
1700  for( i = 0; i < ndiscvars; ++i )
1701  {
1702  assert( SCIPisFeasEQ(scip, SCIPgetVarLbDive(scip, allvars[i]), SCIPgetVarUbDive(scip, allvars[i])) );
1703  }
1704  /* solve LP */
1705  SCIPdebugMsg(scip, " -> old LP iterations: %" SCIP_LONGINT_FORMAT "\n", SCIPgetNLPIterations(scip));
1706 
1707  /* Errors in the LP solver should not kill the overall solving process, if the LP is just needed for a heuristic.
1708  * Hence in optimized mode, the return code is caught and a warning is printed, only in debug mode, SCIP will stop. */
1709 #ifdef NDEBUG
1710  retstat = SCIPsolveDiveLP(scip, -1, &lperror, NULL);
1711  if( retstat != SCIP_OKAY )
1712  {
1713  SCIPwarningMessage(scip, "Error while solving LP in Twoopt heuristic; LP solve terminated with code <%d>\n",retstat);
1714  }
1715 #else
1716  SCIP_CALL( SCIPsolveDiveLP(scip, -1, &lperror, NULL) );
1717 #endif
1718 
1719  SCIPdebugMsg(scip, " -> new LP iterations: %" SCIP_LONGINT_FORMAT "\n", SCIPgetNLPIterations(scip));
1720  SCIPdebugMsg(scip, " -> error=%u, status=%d\n", lperror, SCIPgetLPSolstat(scip));
1721 
1722  /* check if this is a feasible solution */
1723  if( !lperror && SCIPgetLPSolstat(scip) == SCIP_LPSOLSTAT_OPTIMAL )
1724  {
1725  SCIP_Bool success;
1726 
1727  /* copy the current LP solution to the working solution */
1728  SCIP_CALL( SCIPlinkLPSol(scip, worksol) );
1729 
1730  /* check solution for feasibility */
1731 #ifndef NDEBUG
1732  SCIP_CALL( SCIPtrySol(scip, worksol, FALSE, FALSE, TRUE, TRUE, TRUE, &success) );
1733 #else
1734  SCIP_CALL( SCIPtrySol(scip, worksol, FALSE, FALSE, FALSE, FALSE, TRUE, &success) );
1735 #endif
1736 
1737  if( success )
1738  {
1739  SCIPdebugMsg(scip, "found feasible shifted solution:\n");
1740  SCIPdebug( SCIP_CALL( SCIPprintSol(scip, worksol, NULL, FALSE) ) );
1741  heurdata->lastsolindex = SCIPsolGetIndex(bestsol);
1742  *result = SCIP_FOUNDSOL;
1743 
1744 #ifdef SCIP_STATISTIC
1745  SCIPstatisticMessage("*** Twoopt improved solution found by %10s . \n",
1746  SCIPsolGetHeur(bestsol) != NULL ? SCIPheurGetName(SCIPsolGetHeur(bestsol)) :"Tree");
1747 #endif
1748  }
1749  }
1750 
1751  /* terminate the diving */
1752  SCIP_CALL( SCIPendDive(scip) );
1753  }
1754 
1755  TERMINATE:
1756  SCIPdebugMsg(scip, "Termination of Twoopt heuristic\n");
1757  SCIPfreeBufferArray(scip, &activities);
1758  SCIP_CALL( SCIPfreeSol(scip, &worksol) );
1759 
1760  return SCIP_OKAY;
1761 }
1762 
1763 /*
1764  * primal heuristic specific interface methods
1765  */
1766 
1767 /** creates the twoopt primal heuristic and includes it in SCIP */
1769  SCIP* scip /**< SCIP data structure */
1770  )
1771 {
1772  SCIP_HEURDATA* heurdata;
1773  SCIP_HEUR* heur;
1774 
1775  /* create Twoopt primal heuristic data */
1776  SCIP_CALL( SCIPallocBlockMemory(scip, &heurdata) );
1777 
1778  /* include primal heuristic */
1779  SCIP_CALL( SCIPincludeHeurBasic(scip, &heur,
1781  HEUR_MAXDEPTH, HEUR_TIMING, HEUR_USESSUBSCIP, heurExecTwoopt, heurdata) );
1782 
1783  assert(heur != NULL);
1784 
1785  /* set non-NULL pointers to callback methods */
1786  SCIP_CALL( SCIPsetHeurCopy(scip, heur, heurCopyTwoopt) );
1787  SCIP_CALL( SCIPsetHeurFree(scip, heur, heurFreeTwoopt) );
1788  SCIP_CALL( SCIPsetHeurInit(scip, heur, heurInitTwoopt) );
1789  SCIP_CALL( SCIPsetHeurExit(scip, heur, heurExitTwoopt) );
1790  SCIP_CALL( SCIPsetHeurInitsol(scip, heur, heurInitsolTwoopt) );
1791  SCIP_CALL( SCIPsetHeurExitsol(scip, heur, heurExitsolTwoopt) );
1792 
1793  /* include boolean flag intopt */
1794  SCIP_CALL( SCIPaddBoolParam(scip, "heuristics/twoopt/intopt", " Should Integer-2-Optimization be applied or not?",
1795  &heurdata->intopt, TRUE, DEFAULT_INTOPT, NULL, NULL) );
1796 
1797  /* include parameter waitingnodes */
1798  SCIP_CALL( SCIPaddIntParam(scip, "heuristics/twoopt/waitingnodes", "user parameter to determine number of "
1799  "nodes to wait after last best solution before calling heuristic",
1800  &heurdata->waitingnodes, TRUE, DEFAULT_WAITINGNODES, 0, 10000, NULL, NULL));
1801 
1802  /* include parameter maxnslaves */
1803  SCIP_CALL( SCIPaddIntParam(scip, "heuristics/twoopt/maxnslaves", "maximum number of slaves for one master variable",
1804  &heurdata->maxnslaves, TRUE, DEFAULT_MAXNSLAVES, -1, 1000000, NULL, NULL) );
1805 
1806  /* include parameter matchingrate */
1807  SCIP_CALL( SCIPaddRealParam(scip, "heuristics/twoopt/matchingrate",
1808  "parameter to determine the percentage of rows two variables have to share before they are considered equal",
1809  &heurdata->matchingrate, TRUE, DEFAULT_MATCHINGRATE, 0.0, 1.0, NULL, NULL) );
1810 
1811  return SCIP_OKAY;
1812 }
#define SCIPfreeBlockMemoryArray(scip, ptr, num)
Definition: scip_mem.h:97
static SCIP_RETCODE shiftValues(SCIP *scip, SCIP_VAR *master, SCIP_VAR *slave, SCIP_Real mastersolval, DIRECTION masterdir, SCIP_Real slavesolval, DIRECTION slavedir, SCIP_Real shiftval, SCIP_Real *activities, int nrows, SCIP_Bool *feasible)
Definition: heur_twoopt.c:145
SCIP_RETCODE SCIPgetLPColsData(SCIP *scip, SCIP_COL ***cols, int *ncols)
Definition: scip_lp.c:462
#define SCIPreallocBlockMemoryArray(scip, ptr, oldnum, newnum)
Definition: scip_mem.h:86
Primal heuristic to improve incumbent solution by flipping pairs of variables.
SCIP_RETCODE SCIPfreeSol(SCIP *scip, SCIP_SOL **sol)
Definition: scip_sol.c:977
SCIP_Bool SCIProwIsLocal(SCIP_ROW *row)
Definition: lp.c:17265
SCIP_Bool SCIPisPositive(SCIP *scip, SCIP_Real val)
#define SCIPallocBlockMemoryArray(scip, ptr, num)
Definition: scip_mem.h:80
const char * SCIPheurGetName(SCIP_HEUR *heur)
Definition: heur.c:1429
SCIP_RETCODE SCIPsetSolVal(SCIP *scip, SCIP_SOL *sol, SCIP_VAR *var, SCIP_Real val)
Definition: scip_sol.c:1213
public methods for SCIP parameter handling
void SCIPfreeRandom(SCIP *scip, SCIP_RANDNUMGEN **randnumgen)
int SCIPgetNLPRows(SCIP *scip)
Definition: scip_lp.c:596
static SCIP_DECL_HEURFREE(heurFreeTwoopt)
Definition: heur_twoopt.c:834
SCIP_RETCODE SCIPsetHeurExitsol(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEUREXITSOL((*heurexitsol)))
Definition: scip_heur.c:233
public methods for memory management
SCIP_HEURDATA * SCIPheurGetData(SCIP_HEUR *heur)
Definition: heur.c:1340
SCIP_Real SCIPgetVarLbDive(SCIP *scip, SCIP_VAR *var)
Definition: scip_lp.c:2556
SCIP_EXPORT SCIP_Bool SCIPsolIsOriginal(SCIP_SOL *sol)
Definition: sol.c:2521
SCIP_Real * SCIPcolGetVals(SCIP_COL *col)
Definition: lp.c:17025
void SCIPwarningMessage(SCIP *scip, const char *formatstr,...)
Definition: scip_message.c:123
static long bound
SCIP_Real SCIPgetSolVal(SCIP *scip, SCIP_SOL *sol, SCIP_VAR *var)
Definition: scip_sol.c:1353
SCIP_RETCODE SCIPprintRow(SCIP *scip, SCIP_ROW *row, FILE *file)
Definition: scip_lp.c:2152
int SCIPcolGetNNonz(SCIP_COL *col)
Definition: lp.c:16990
#define DEFAULT_WAITINGNODES
Definition: heur_twoopt.c:59
#define DEFAULT_MAXNSLAVES
Definition: heur_twoopt.c:63
int SCIPgetNVars(SCIP *scip)
Definition: scip_prob.c:1986
#define DEFAULT_INTOPT
Definition: heur_twoopt.c:58
#define FALSE
Definition: def.h:73
SCIP_ROW ** SCIPcolGetRows(SCIP_COL *col)
Definition: lp.c:17015
static SCIP_RETCODE optimize(SCIP *scip, SCIP_SOL *worksol, SCIP_VAR **vars, int *blockstart, int *blockend, int nblocks, OPTTYPE opttype, SCIP_Real *activities, int nrows, SCIP_Bool *improvement, SCIP_Bool *varboundserr, SCIP_HEURDATA *heurdata)
Definition: heur_twoopt.c:914
SCIP_EXPORT SCIP_Real SCIPvarGetObj(SCIP_VAR *var)
Definition: var.c:17515
SCIP_EXPORT SCIP_HEUR * SCIPsolGetHeur(SCIP_SOL *sol)
Definition: sol.c:2604
#define HEUR_FREQ
Definition: heur_twoopt.c:50
SCIP_EXPORT SCIP_VARTYPE SCIPvarGetType(SCIP_VAR *var)
Definition: var.c:17182
#define TRUE
Definition: def.h:72
#define SCIPdebug(x)
Definition: pub_message.h:84
enum SCIP_Retcode SCIP_RETCODE
Definition: type_retcode.h:54
SCIP_RETCODE SCIPlinkLPSol(SCIP *scip, SCIP_SOL *sol)
Definition: scip_sol.c:1018
#define SCIPstatisticMessage
Definition: pub_message.h:114
SCIP_Real SCIPgetVarUbDive(SCIP *scip, SCIP_VAR *var)
Definition: scip_lp.c:2585
SCIP_RETCODE SCIPchgVarLbDive(SCIP *scip, SCIP_VAR *var, SCIP_Real newbound)
Definition: scip_lp.c:2359
SCIP_Bool SCIPisFeasLE(SCIP *scip, SCIP_Real val1, SCIP_Real val2)
struct SCIP_HeurData SCIP_HEURDATA
Definition: type_heur.h:67
public methods for problem variables
SCIP_RETCODE SCIPaddBoolParam(SCIP *scip, const char *name, const char *desc, SCIP_Bool *valueptr, SCIP_Bool isadvanced, SCIP_Bool defaultvalue, SCIP_DECL_PARAMCHGD((*paramchgd)), SCIP_PARAMDATA *paramdata)
Definition: scip_param.c:48
#define SCIPfreeBlockMemory(scip, ptr)
Definition: scip_mem.h:95
#define HEUR_FREQOFS
Definition: heur_twoopt.c:51
static SCIP_DECL_SORTPTRCOMP(SCIPvarcolComp)
Definition: heur_twoopt.c:293
SCIP_EXPORT SCIP_VARSTATUS SCIPvarGetStatus(SCIP_VAR *var)
Definition: var.c:17136
#define HEUR_NAME
Definition: heur_twoopt.c:46
int SCIProwGetLPPos(SCIP_ROW *row)
Definition: lp.c:17365
#define HEUR_TIMING
Definition: heur_twoopt.c:54
#define SCIPfreeBufferArray(scip, ptr)
Definition: scip_mem.h:123
#define SCIPallocBlockMemory(scip, ptr)
Definition: scip_mem.h:78
SCIP_RETCODE SCIPsolveDiveLP(SCIP *scip, int itlim, SCIP_Bool *lperror, SCIP_Bool *cutoff)
Definition: scip_lp.c:2618
SCIP_RETCODE SCIPsetHeurInit(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEURINIT((*heurinit)))
Definition: scip_heur.c:185
SCIP_RETCODE SCIPtrySol(SCIP *scip, SCIP_SOL *sol, SCIP_Bool printreason, SCIP_Bool completely, SCIP_Bool checkbounds, SCIP_Bool checkintegrality, SCIP_Bool checklprows, SCIP_Bool *stored)
Definition: scip_sol.c:3126
#define SCIPdebugMsg
Definition: scip_message.h:69
SCIP_Bool SCIPisFeasIntegral(SCIP *scip, SCIP_Real val)
SCIP_LPSOLSTAT SCIPgetLPSolstat(SCIP *scip)
Definition: scip_lp.c:159
SCIP_Bool SCIPhasCurrentNodeLP(SCIP *scip)
Definition: scip_lp.c:74
SCIP_Bool SCIPisInfinity(SCIP *scip, SCIP_Real val)
static SCIP_DECL_HEURINITSOL(heurInitsolTwoopt)
Definition: heur_twoopt.c:1375
int SCIPgetNIntVars(SCIP *scip)
Definition: scip_prob.c:2076
public methods for numerical tolerances
SCIP_RETCODE SCIPcreateRandom(SCIP *scip, SCIP_RANDNUMGEN **randnumgen, unsigned int initialseed, SCIP_Bool useglobalseed)
Direction
Definition: heur_twoopt.c:128
public methods for querying solving statistics
SCIP_RETCODE SCIPincludeHeurBasic(SCIP *scip, SCIP_HEUR **heur, const char *name, const char *desc, char dispchar, int priority, int freq, int freqofs, int maxdepth, SCIP_HEURTIMING timingmask, SCIP_Bool usessubscip, SCIP_DECL_HEUREXEC((*heurexec)), SCIP_HEURDATA *heurdata)
Definition: scip_heur.c:108
#define DEFAULT_RANDSEED
Definition: heur_twoopt.c:65
static SCIP_DECL_HEURINIT(heurInitTwoopt)
Definition: heur_twoopt.c:854
SCIP_Longint SCIPgetNNodes(SCIP *scip)
SCIP_RETCODE SCIPcreateSolCopy(SCIP *scip, SCIP_SOL **sol, SCIP_SOL *sourcesol)
Definition: scip_sol.c:610
#define SCIPduplicateBlockMemoryArray(scip, ptr, source, num)
Definition: scip_mem.h:92
static SCIP_DECL_HEUREXIT(heurExitTwoopt)
Definition: heur_twoopt.c:1278
static SCIP_RETCODE presolveTwoOpt(SCIP *scip, SCIP_HEUR *heur, SCIP_HEURDATA *heurdata)
Definition: heur_twoopt.c:739
SCIP_EXPORT const char * SCIPvarGetName(SCIP_VAR *var)
Definition: var.c:17017
SCIP_EXPORT void SCIPsolSetHeur(SCIP_SOL *sol, SCIP_HEUR *heur)
Definition: sol.c:2649
SCIP_EXPORT SCIP_Bool SCIPvarIsIntegral(SCIP_VAR *var)
Definition: var.c:17208
void SCIPcolSort(SCIP_COL *col)
Definition: lp.c:3424
SCIP_RETCODE SCIPgetLPRowsData(SCIP *scip, SCIP_ROW ***rows, int *nrows)
Definition: scip_lp.c:540
SCIP_Bool SCIPisFeasEQ(SCIP *scip, SCIP_Real val1, SCIP_Real val2)
SCIP_RETCODE SCIPstartDive(SCIP *scip)
Definition: scip_lp.c:2182
SCIP_VAR ** SCIPgetVars(SCIP *scip)
Definition: scip_prob.c:1941
static SCIP_DECL_HEUREXEC(heurExecTwoopt)
Definition: heur_twoopt.c:1471
int SCIProwGetIndex(SCIP_ROW *row)
Definition: lp.c:17225
SCIP_Bool SCIPisZero(SCIP *scip, SCIP_Real val)
void SCIPheurSetData(SCIP_HEUR *heur, SCIP_HEURDATA *heurdata)
Definition: heur.c:1350
#define NULL
Definition: lpi_spx1.cpp:155
SCIP_EXPORT void SCIPsortRealPtrPtrInt(SCIP_Real *realarray, void **ptrarray1, void **ptrarray2, int *intarray, int len)
public methods for primal CIP solutions
static int varColCompare(SCIP_VAR *var1, SCIP_VAR *var2)
Definition: heur_twoopt.c:250
#define SCIP_CALL(x)
Definition: def.h:370
SCIP_Real SCIPfeasFloor(SCIP *scip, SCIP_Real val)
SCIP_EXPORT void SCIPsortPtr(void **ptrarray, SCIP_DECL_SORTPTRCOMP((*ptrcomp)), int len)
public methods for primal heuristic plugins and divesets
SCIP_Bool SCIPisFeasZero(SCIP *scip, SCIP_Real val)
SCIP_EXPORT SCIP_COL * SCIPvarGetCol(SCIP_VAR *var)
Definition: var.c:17381
#define SCIPallocBufferArray(scip, ptr, num)
Definition: scip_mem.h:111
public data structures and miscellaneous methods
int SCIPrandomGetInt(SCIP_RANDNUMGEN *randnumgen, int minrandval, int maxrandval)
Definition: misc.c:9959
SCIP_RETCODE SCIPendDive(SCIP *scip)
Definition: scip_lp.c:2231
#define SCIP_Bool
Definition: def.h:70
#define DEFAULT_ARRAYSIZE
Definition: heur_twoopt.c:64
SCIP_RETCODE SCIPsetHeurExit(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEUREXIT((*heurexit)))
Definition: scip_heur.c:201
#define HEUR_DESC
Definition: heur_twoopt.c:47
SCIP_EXPORT SCIP_Real SCIPvarGetUbGlobal(SCIP_VAR *var)
Definition: var.c:17677
#define MAX(x, y)
Definition: tclique_def.h:83
SCIP_Real SCIProwGetLhs(SCIP_ROW *row)
Definition: lp.c:17156
static SCIP_RETCODE innerPresolve(SCIP *scip, SCIP_VAR **vars, SCIP_VAR ***varspointer, int nvars, int *nblocks, int *maxblocksize, int *nblockvars, int **blockstart, int **blockend, SCIP_HEUR *heur, SCIP_HEURDATA *heurdata)
Definition: heur_twoopt.c:640
SCIP_RETCODE SCIPchgVarUbDive(SCIP *scip, SCIP_VAR *var, SCIP_Real newbound)
Definition: scip_lp.c:2391
public methods for LP management
SCIP_EXPORT int SCIPsolGetIndex(SCIP_SOL *sol)
Definition: sol.c:2635
SCIP_Bool SCIPisNegative(SCIP *scip, SCIP_Real val)
enum Direction DIRECTION
Definition: heur_twoopt.c:134
Opttype
Definition: heur_twoopt.c:120
SCIP_Bool SCIPisFeasGE(SCIP *scip, SCIP_Real val1, SCIP_Real val2)
SCIP_EXPORT SCIP_Real SCIPvarGetLbLocal(SCIP_VAR *var)
Definition: var.c:17723
SCIP_RETCODE SCIPaddRealParam(SCIP *scip, const char *name, const char *desc, SCIP_Real *valueptr, SCIP_Bool isadvanced, SCIP_Real defaultvalue, SCIP_Real minvalue, SCIP_Real maxvalue, SCIP_DECL_PARAMCHGD((*paramchgd)), SCIP_PARAMDATA *paramdata)
Definition: scip_param.c:130
#define DEFAULT_MATCHINGRATE
Definition: heur_twoopt.c:60
public methods for the LP relaxation, rows and columns
enum Opttype OPTTYPE
Definition: heur_twoopt.c:125
SCIP_EXPORT SCIP_Real SCIPvarGetUbLocal(SCIP_VAR *var)
Definition: var.c:17733
methods for sorting joint arrays of various types
SCIP_VAR ** b
Definition: circlepacking.c:56
static SCIP_DECL_HEURCOPY(heurCopyTwoopt)
Definition: heur_twoopt.c:820
#define HEUR_MAXDEPTH
Definition: heur_twoopt.c:52
SCIP_Bool SCIPisFeasGT(SCIP *scip, SCIP_Real val1, SCIP_Real val2)
SCIP_Longint SCIPgetNLPIterations(SCIP *scip)
static void disposeVariable(SCIP_VAR **vars, int *blockend, int varindex)
Definition: heur_twoopt.c:625
public methods for solutions
public methods for random numbers
SCIP_EXPORT SCIP_Real SCIPvarGetLbGlobal(SCIP_VAR *var)
Definition: var.c:17667
SCIP_RETCODE SCIPsetHeurCopy(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEURCOPY((*heurcopy)))
Definition: scip_heur.c:153
SCIP_Bool SCIPisFeasLT(SCIP *scip, SCIP_Real val1, SCIP_Real val2)
SCIP_EXPORT SCIP_Longint SCIPsolGetNodenum(SCIP_SOL *sol)
Definition: sol.c:2584
public methods for message output
SCIP_RETCODE SCIPgetVarsData(SCIP *scip, SCIP_VAR ***vars, int *nvars, int *nbinvars, int *nintvars, int *nimplvars, int *ncontvars)
Definition: scip_prob.c:1860
SCIP_RETCODE SCIPaddIntParam(SCIP *scip, const char *name, const char *desc, int *valueptr, SCIP_Bool isadvanced, int defaultvalue, int minvalue, int maxvalue, SCIP_DECL_PARAMCHGD((*paramchgd)), SCIP_PARAMDATA *paramdata)
Definition: scip_param.c:74
SCIP_RETCODE SCIPprintSol(SCIP *scip, SCIP_SOL *sol, FILE *file, SCIP_Bool printzeros)
Definition: scip_sol.c:1767
#define SCIP_Real
Definition: def.h:163
#define HEUR_PRIORITY
Definition: heur_twoopt.c:49
const char * SCIProwGetName(SCIP_ROW *row)
Definition: lp.c:17215
public methods for message handling
#define HEUR_USESSUBSCIP
Definition: heur_twoopt.c:55
SCIP_RETCODE SCIPsetHeurInitsol(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEURINITSOL((*heurinitsol)))
Definition: scip_heur.c:217
int SCIPgetNBinVars(SCIP *scip)
Definition: scip_prob.c:2031
SCIP_RETCODE SCIPsetHeurFree(SCIP *scip, SCIP_HEUR *heur, SCIP_DECL_HEURFREE((*heurfree)))
Definition: scip_heur.c:169
SCIP_Real SCIProwGetRhs(SCIP_ROW *row)
Definition: lp.c:17166
public methods for primal heuristics
#define HEUR_DISPCHAR
Definition: heur_twoopt.c:48
public methods for global and local (sub)problems
static SCIP_DECL_HEUREXITSOL(heurExitsolTwoopt)
Definition: heur_twoopt.c:1408
SCIP_SOL * SCIPgetBestSol(SCIP *scip)
Definition: scip_sol.c:2305
SCIP_RETCODE SCIPincludeHeurTwoopt(SCIP *scip)
Definition: heur_twoopt.c:1769
static SCIP_Bool checkConstraintMatching(SCIP *scip, SCIP_VAR *var1, SCIP_VAR *var2, SCIP_Real matchingrate)
Definition: heur_twoopt.c:302
static SCIP_Real determineBound(SCIP *scip, SCIP_SOL *sol, SCIP_VAR *master, DIRECTION masterdirection, SCIP_VAR *slave, DIRECTION slavedirection, SCIP_Real *activities, int nrows)
Definition: heur_twoopt.c:400
#define SCIPreallocBufferArray(scip, ptr, num)
Definition: scip_mem.h:115
SCIP_Real SCIPgetRowSolActivity(SCIP *scip, SCIP_ROW *row, SCIP_SOL *sol)
Definition: scip_lp.c:2084
memory allocation routines