Scippy

SCIP

Solving Constraint Integer Programs

pricer_coloring.h
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4 /* SCIP --- Solving Constraint Integer Programs */
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24 
25 /**@file pricer_coloring.h
26  * @brief variable pricer for the vertex coloring problem
27  * @author Gerald Gamrath
28  *
29  * This file implements the pricer for the coloring algorithm.
30  *
31  * It computes maximal stable sets in the current graph whose corresponding variables can improve
32  * the current LP solution. This is done by computing a maximum weighted stable set in the current
33  * graph with dual-variables of the node constraints as weights. A variable can improve the
34  * solution, if the weight of the corresponding stable set is larger than 1, since it then has
35  * negative reduced costs, which are given by (1 - weight of the set).
36  *
37  * The pricer first tries to compute such a stable set using a a greedy-method. If it fails, the tclique-algorithm is
38  * used on the complementary graph. This is a branch-and-bound based algorithm for maximal cliques,
39  * included in SCIP. In this case, not only the best solution is added to the LP, but also all other
40  * stable sets found during the branch-and-bound process that could improve the current LP solution
41  * are added, limited to a maximal number that can be changed by a parameter.
42  */
43 
44 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
45 
46 #ifndef __SCIP_PRICER_COLORING__
47 #define __SCIP_PRICER_COLORING__
48 
49 #include "probdata_coloring.h"
50 
51 #ifdef __cplusplus
52 extern "C" {
53 #endif
54 
55 /** creates the healthcare variable pricer and includes it in SCIP */
57  SCIP* scip /**< SCIP data structure */
58  );
59 
60 /** sets the way, the pricer handles variables with negative reduced costs found during the tclique-algorithm
61  if onlybest is true, only the best n variables are added to the lp, while onlybest = false means, that
62  the first n variables with negative reduced costs are added
63  Here, n is the value set by setNVarsCreatedPerRound */
65  SCIP* scip, /**< SCIP data structure */
66  SCIP_Bool onlybest /**< true, if only the best vars should be used */
67  );
68 
69 
70 /* sets, whether the pricing should use the greedy-method */
72  SCIP* scip, /**< SCIP data structure */
73  SCIP_Bool usegreedy /**< true, if the greedy should be used */
74  );
75 
76 
77 /* sets whether the pricing should use the tclique-method for finding new variables */
79  SCIP* scip, /**< SCIP data structure */
80  SCIP_Bool usetclique /**< true, if the tclique-algorithm should be used */
81  );
82 
83 
84 /* sets the number of variables that the pricer is allowed to create in one round of pricing */
86  SCIP* scip, /**< SCIP data structure */
87  int nvars /**< maximal number of variables that should be created in one round */
88  );
89 
90 #ifdef __cplusplus
91 }
92 #endif
93 
94 #endif
problem data for vertex coloring algorithm
void COLORpricerUseTclique(SCIP *scip, SCIP_Bool usetclique)
enum SCIP_Retcode SCIP_RETCODE
Definition: type_retcode.h:63
void COLORpricerUseGreedy(SCIP *scip, SCIP_Bool usegreedy)
void COLORpricerSetNVarsCreatedPerRound(SCIP *scip, int nvars)
#define SCIP_Bool
Definition: def.h:93
void COLORpricerUseOnlyBestStableSets(SCIP *scip, SCIP_Bool onlybest)
SCIP_RETCODE SCIPincludePricerColoring(SCIP *scip)