Scippy

SCIP

Solving Constraint Integer Programs

presolve.h
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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 2002-2022 Zuse Institute Berlin */
7 /* */
8 /* Licensed under the Apache License, Version 2.0 (the "License"); */
9 /* you may not use this file except in compliance with the License. */
10 /* You may obtain a copy of the License at */
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19 /* */
20 /* You should have received a copy of the Apache-2.0 license */
21 /* along with SCIP; see the file LICENSE. If not visit scipopt.org. */
22 /* */
23 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
24 
25 /**@file presolve.h
26  * @ingroup PUBLICCOREAPI
27  * @brief methods commonly used for presolving
28  * @author Michael Winkler
29  */
30 
31 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
32 
33 #ifndef __SCIP_PRESOLVE_H__
34 #define __SCIP_PRESOLVE_H__
35 
36 #include "scip/def.h"
37 #include "scip/type_retcode.h"
38 #include "scip/type_scip.h"
39 #include "scip/type_var.h"
40 
41 #ifdef __cplusplus
42 extern "C" {
43 #endif
44 
45 /**@defgroup PublicSpecialPresolveMethods Special Methods
46  * @ingroup PublicPresolverMethods
47  * @brief methods commonly used for presolving
48  *
49  * @{
50  */
51 /** try to reduce the necessary variable in a set of variables with corresponding bounds and boundtypes for which one
52  * must be fulfilled
53  *
54  * e.g. a set of logicor or bounddisjunctive constraint variables would be such a set
55  *
56  * consider the following set:
57  *
58  * x1 >= 1, x2 >= 3, x3 >= 1, x4 <= 0
59  *
60  * by (global) implication data (cliques, implications, and variable bounds) we have also the following implications
61  * given:
62  *
63  * x1 >= 1 => x3 >= 1
64  * x2 >= 2 => x3 >= 1
65  * x4 <= 0 => x1 >= 1
66  *
67  * Because of the last implication x4 is redundant, because x1 >= 1 would also be fulfilled in the variable set, so we
68  * can reduce the set by x4.
69  * Also, the both other implications and x3 >= 1 (in the given variable set) all imply exactly x3 >= 1, so we tighten
70  * the global lower bound of x3 to 1 and the set of variables gets redundant.
71  */
72 SCIP_EXPORT
74  SCIP* scip, /**< SCIP data structure */
75  SCIP_VAR** vars, /**< variables array for which at least one must be fulfilled in the
76  * following bounds and boundtypes */
77  SCIP_Real* bounds, /**< bounds array for which at least one must be fulfilled */
78  SCIP_Bool* boundtypes, /**< boundtypes array (TRUE == SCIP_BOUNDTYPE_UPPER, FALSE == SCIP_BOUNDTYPE_LOWER)
79  * for which at least one must be fulfilled */
80  SCIP_Bool* redundants, /**< array which be filled and then indicate if a variable in the set is redundant */
81  int nvars, /**< number of variables */
82  int* nredvars, /**< pointer to store how many variables can be removed */
83  int* nglobalred, /**< pointer to store number of global reductions on variable bounds found
84  * through this set of variables */
85  SCIP_Bool* setredundant, /**< pointer to store if we found a global reduction on a variable which was part
86  * of the given set of variables, this makes this disjunction redundant */
87  SCIP_Bool* glbinfeas, /**< pointer to store if global infeasibility was detected */
88  SCIP_Bool fullshortening /**< do we want to try the shortening procedure over the whole set (which might be expensive) */
89  );
90 
91 /** @} */
92 
93 #ifdef __cplusplus
94 }
95 #endif
96 
97 #endif
enum SCIP_Retcode SCIP_RETCODE
Definition: type_retcode.h:63
type definitions for return codes for SCIP methods
type definitions for SCIP&#39;s main datastructure
type definitions for problem variables
#define SCIP_Bool
Definition: def.h:93
#define SCIP_Real
Definition: def.h:186
SCIP_RETCODE SCIPshrinkDisjunctiveVarSet(SCIP *scip, SCIP_VAR **vars, SCIP_Real *bounds, SCIP_Bool *boundtypes, SCIP_Bool *redundants, int nvars, int *nredvars, int *nglobalred, SCIP_Bool *setredundant, SCIP_Bool *glbinfeas, SCIP_Bool fullshortening)
Definition: presolve.c:995
common defines and data types used in all packages of SCIP