pricer_coloring.h File Reference

Detailed Description

variable pricer for the vertex coloring problem

Author

Gerald Gamrath

This file implements the pricer for the coloring algorithm.

It computes maximal stable sets in the current graph whose corresponding variables can improve the current LP solution. This is done by computing a maximum weighted stable set in the current graph with dual-variables of the node constraints as weights. A variable can improve the solution, if the weight of the corresponding stable set is larger than 1, since it then has negative reduced costs, which are given by (1 - weight of the set).

The pricer first tries to compute such a stable set using a a greedy-method. If it fails, the tclique-algorithm is used on the complementary graph. This is a branch-and-bound based algorithm for maximal cliques, included in SCIP. In this case, not only the best solution is added to the LP, but also all other stable sets found during the branch-and-bound process that could improve the current LP solution are added, limited to a maximal number that can be changed by a parameter.

Definition in file pricer_coloring.h.

#include "probdata_coloring.h"

Go to the source code of this file.

Functions
SCIP_RETCODE	SCIPincludePricerColoring (SCIP *scip)
void	COLORpricerUseOnlyBestStableSets (SCIP *scip, SCIP_Bool onlybest)
void	COLORpricerUseGreedy (SCIP *scip, SCIP_Bool usegreedy)
void	COLORpricerUseTclique (SCIP *scip, SCIP_Bool usetclique)
void	COLORpricerSetNVarsCreatedPerRound (SCIP *scip, int nvars)

Function Documentation

SCIPincludePricerColoring()

SCIP_RETCODE SCIPincludePricerColoring

(

SCIP *

scip

)

creates the healthcare variable pricer and includes it in SCIP

creates the coloring variable pricer and includes it in SCIP

Parameters

scip	SCIP data structure

Definition at line 875 of file pricer_coloring.c.

References DEFAULT_MAXROUNDSNODE, DEFAULT_MAXROUNDSROOT, DEFAULT_MAXTCLIQUENODES, DEFAULT_MAXVARSROUND, DEFAULT_ONLYBEST, DEFAULT_USEGREEDY, DEFAULT_USETCLIQUE, FALSE, NULL, PRICER_DELAY, PRICER_DESC, PRICER_NAME, PRICER_PRIORITY, SCIP_CALL, SCIP_OKAY, SCIPaddBoolParam(), SCIPaddIntParam(), SCIPallocBlockMemory, SCIPincludePricerBasic(), SCIPsetPricerCopy(), SCIPsetPricerExitsol(), SCIPsetPricerFree(), SCIPsetPricerInitsol(), and TRUE.

Referenced by SCIPincludeColoringPlugins().

COLORpricerUseOnlyBestStableSets()

void COLORpricerUseOnlyBestStableSets	(	SCIP *	scip,
		SCIP_Bool	onlybest
	)

sets the way, the pricer handles variables with negative reduced costs found during the tclique-algorithm if onlybest is true, only the best n variables are added to the lp, while onlybest = false means, that the first n variables with negative reduced costs are added Here, n is the value set by setNVarsCreatedPerRound

Parameters

scip	SCIP data structure
onlybest	true, if only the best vars should be used

COLORpricerUseGreedy()

void COLORpricerUseGreedy	(	SCIP *	scip,
		SCIP_Bool	usegreedy
	)

Parameters

scip	SCIP data structure
usegreedy	true, if the greedy should be used

COLORpricerUseTclique()

void COLORpricerUseTclique	(	SCIP *	scip,
		SCIP_Bool	usetclique
	)

Parameters

scip	SCIP data structure
usetclique	true, if the tclique-algorithm should be used

COLORpricerSetNVarsCreatedPerRound()

void COLORpricerSetNVarsCreatedPerRound	(	SCIP *	scip,
		int	nvars
	)

Parameters

scip	SCIP data structure
nvars	maximal number of variables that should be created in one round