Detailed Description

LNS heuristic that finds the optimal rounding to a given point.

Author: Timo Berthold

Definition in file heur_rens.c.

#include <assert.h>
#include <string.h>
#include <stdio.h>
#include "scip/scip.h"
#include "scip/heur_rens.h"
#include "scip/scipdefplugins.h"
#include "scip/cons_linear.h"
#include "scip/pub_misc.h"

Go to the source code of this file.

Macros
#define	HEUR_NAME "rens"

#define	HEUR_DESC "LNS exploring fractional neighborhood of relaxation's optimum"

#define	HEUR_DISPCHAR 'E'

#define	HEUR_PRIORITY -1100000

#define	HEUR_FREQ 0

#define	HEUR_FREQOFS 0

#define	HEUR_MAXDEPTH -1

#define	HEUR_TIMING SCIP_HEURTIMING_AFTERLPNODE

#define	HEUR_USESSUBSCIP TRUE

#define	DEFAULT_BINARYBOUNDS TRUE /* should general integers get binary bounds [floor(.),ceil(.)] ? */

#define	DEFAULT_MAXNODES 5000LL /* maximum number of nodes to regard in the subproblem */

#define	DEFAULT_MINFIXINGRATE 0.5 /* minimum percentage of integer variables that have to be fixed */

#define	DEFAULT_MINIMPROVE 0.01 /* factor by which RENS should at least improve the incumbent */

#define	DEFAULT_MINNODES 50LL /* minimum number of nodes to regard in the subproblem */

#define	DEFAULT_NODESOFS 500LL /* number of nodes added to the contingent of the total nodes */

#define	DEFAULT_NODESQUOT 0.1 /* subproblem nodes in relation to nodes of the original problem */

#define	DEFAULT_LPLIMFAC 2.0 /* factor by which the limit on the number of LP depends on the node limit */

#define	DEFAULT_STARTSOL 'l' /* solution that is used for fixing values */

#define	STARTSOL_CHOICES "nl" /* possible values for startsol ('l'p relaxation, 'n'lp relaxation) */

#define	DEFAULT_USELPROWS

#define	DEFAULT_COPYCUTS

#define	DEFAULT_EXTRATIME

#define	DEFAULT_ADDALLSOLS FALSE /* should all subproblem solutions be added to the original SCIP? */

#define	DEFAULT_FULLSCALE

#define	EVENTHDLR_NAME "Rens"

#define	EVENTHDLR_DESC "LP event handler for "HEUR_NAME" heuristic"

Functions
static SCIP_RETCODE	computeFixingrate (SCIP scip, SCIP_Real minfixingrate, char startsol, SCIP_Real fixingrate, SCIP_Bool success)

static SCIP_RETCODE	createSubproblem (SCIP scip, SCIP subscip, SCIP_VAR **subvars, char startsol, SCIP_Bool binarybounds, SCIP_Bool uselprows)

static SCIP_RETCODE	createNewSol (SCIP scip, SCIP subscip, SCIP_VAR *subvars, SCIP_HEUR heur, SCIP_SOL subsol, SCIP_Bool success)

static	SCIP_DECL_EVENTEXEC (eventExecRens)

SCIP_RETCODE	SCIPapplyRens (SCIP scip, SCIP_HEUR heur, SCIP_RESULT *result, SCIP_Real minfixingrate, SCIP_Real minimprove, SCIP_Longint maxnodes, SCIP_Longint nstallnodes, char startsol, SCIP_Bool binarybounds, SCIP_Bool uselprows)

static	SCIP_DECL_HEURCOPY (heurCopyRens)

static	SCIP_DECL_HEURFREE (heurFreeRens)

static	SCIP_DECL_HEURINIT (heurInitRens)

static	SCIP_DECL_HEUREXEC (heurExecRens)

SCIP_RETCODE	SCIPincludeHeurRens (SCIP *scip)

Macro Definition Documentation

#define HEUR_NAME "rens"

Definition at line 33 of file heur_rens.c.

Referenced by SCIP_DECL_HEURCOPY().

#define HEUR_DESC "LNS exploring fractional neighborhood of relaxation's optimum"

Definition at line 34 of file heur_rens.c.

#define HEUR_DISPCHAR 'E'

Definition at line 35 of file heur_rens.c.

#define HEUR_PRIORITY -1100000

Definition at line 36 of file heur_rens.c.

#define HEUR_FREQ 0

Definition at line 37 of file heur_rens.c.

#define HEUR_FREQOFS 0

Definition at line 38 of file heur_rens.c.

#define HEUR_MAXDEPTH -1

Definition at line 39 of file heur_rens.c.

#define HEUR_TIMING SCIP_HEURTIMING_AFTERLPNODE

Definition at line 40 of file heur_rens.c.

#define HEUR_USESSUBSCIP TRUE

does the heuristic use a secondary SCIP instance?

Definition at line 41 of file heur_rens.c.

#define DEFAULT_BINARYBOUNDS TRUE /* should general integers get binary bounds [floor(.),ceil(.)] ? */

Definition at line 44 of file heur_rens.c.

#define DEFAULT_MAXNODES 5000LL /* maximum number of nodes to regard in the subproblem */

Definition at line 45 of file heur_rens.c.

#define DEFAULT_MINFIXINGRATE 0.5 /* minimum percentage of integer variables that have to be fixed */

Definition at line 46 of file heur_rens.c.

#define DEFAULT_MINIMPROVE 0.01 /* factor by which RENS should at least improve the incumbent */

Definition at line 47 of file heur_rens.c.

#define DEFAULT_MINNODES 50LL /* minimum number of nodes to regard in the subproblem */

Definition at line 48 of file heur_rens.c.

#define DEFAULT_NODESOFS 500LL /* number of nodes added to the contingent of the total nodes */

Definition at line 49 of file heur_rens.c.

#define DEFAULT_NODESQUOT 0.1 /* subproblem nodes in relation to nodes of the original problem */

Definition at line 50 of file heur_rens.c.

#define DEFAULT_LPLIMFAC 2.0 /* factor by which the limit on the number of LP depends on the node limit */

Definition at line 51 of file heur_rens.c.

#define DEFAULT_STARTSOL 'l' /* solution that is used for fixing values */

Definition at line 52 of file heur_rens.c.

#define STARTSOL_CHOICES "nl" /* possible values for startsol ('l'p relaxation, 'n'lp relaxation) */

Definition at line 53 of file heur_rens.c.

#define DEFAULT_USELPROWS

Value:

FALSE /* should subproblem be created out of the rows in the LP rows,

* otherwise, the copy constructors of the constraints handlers are used */

Definition at line 54 of file heur_rens.c.

#define DEFAULT_COPYCUTS

Value:

TRUE      /* if DEFAULT_USELPROWS is FALSE, then should all active cuts from the cutpool
                                         * of the original scip be copied to constraints of the subscip
                                         */

Definition at line 55 of file heur_rens.c.

#define DEFAULT_EXTRATIME

Value:

FALSE      /* should the RENS sub-CIP get its own full time limit? This is only
                                         * implemented for testing and not recommended to be used!
                                         */

Definition at line 56 of file heur_rens.c.

#define DEFAULT_ADDALLSOLS FALSE /* should all subproblem solutions be added to the original SCIP? */

Definition at line 57 of file heur_rens.c.

#define DEFAULT_FULLSCALE

Value:

FALSE      /* should the RENS sub-CIP be solved with full-scale SCIP settings, including
                                         * techniques that merely work on the dual bound, e.g., cuts?  This is only
                                         * implemented for testing and not recommended to be used!
                                         */

Definition at line 59 of file heur_rens.c.

#define EVENTHDLR_NAME "Rens"

Definition at line 62 of file heur_rens.c.

Referenced by SCIP_DECL_EVENTEXEC().

#define EVENTHDLR_DESC "LP event handler for "HEUR_NAME" heuristic"

Definition at line 63 of file heur_rens.c.

Function Documentation

static SCIP_RETCODE computeFixingrate	(	SCIP *	scip,
		SCIP_Real	minfixingrate,
		char *	startsol,
		SCIP_Real *	fixingrate,
		SCIP_Bool *	success
	)

static

compute the number of initial fixings and check whether the fixing rate exceeds the minimum fixing rate

Parameters

scip	SCIP data structure
minfixingrate	percentage of integer variables that have to be fixed
startsol	pointer to solution used for fixing values ('l'p relaxation, 'n'lp relaxation)
fixingrate	percentage of integers that get actually fixed
success	pointer to store whether minimum fixingrate is exceeded

Definition at line 101 of file heur_rens.c.

References FALSE, MAX, NULL, SCIP_CALL, SCIP_NLPPAR_VERBLEVEL, SCIP_NLPSOLSTAT_FEASIBLE, SCIP_NLPSOLSTAT_GLOBOPT, SCIP_NLPSOLSTAT_LOCOPT, SCIP_OKAY, SCIP_Real, SCIPdebug, SCIPdebugMessage, SCIPgetNLPBranchCands(), SCIPgetNLPIntPar(), SCIPgetNLPSolstat(), SCIPgetNPseudoBranchCands(), SCIPgetVarsData(), SCIPisFeasIntegral(), SCIPisNLPConstructed(), SCIPsetNLPInitialGuessSol(), SCIPsetNLPIntPar(), SCIPsolveNLP(), and SCIPvarGetNLPSol().

static SCIP_RETCODE createSubproblem	(	SCIP *	scip,
		SCIP *	subscip,
		SCIP_VAR **	subvars,
		char	startsol,
		SCIP_Bool	binarybounds,
		SCIP_Bool	uselprows
	)

static

creates a subproblem by fixing a number of variables

Parameters

scip	original SCIP data structure
subscip	SCIP data structure for the subproblem
subvars	the variables of the subproblem
startsol	solution used for fixing values ('l'p relaxation, 'n'lp relaxation)
binarybounds	should general integers get binary bounds [floor(.),ceil(.)] ?
uselprows	should subproblem be created out of the rows in the LP rows?

Definition at line 200 of file heur_rens.c.

static SCIP_RETCODE createNewSol	(	SCIP *	scip,
		SCIP *	subscip,
		SCIP_VAR **	subvars,
		SCIP_HEUR *	heur,
		SCIP_SOL *	subsol,
		SCIP_Bool *	success
	)

static

creates a new solution for the original problem by copying the solution of the subproblem

Parameters

scip	original SCIP data structure
subscip	SCIP structure of the subproblem
subvars	the variables of the subproblem
heur	RENS heuristic structure
subsol	solution of the subproblem
success	used to store whether new solution was found or not

Definition at line 320 of file heur_rens.c.

static SCIP_DECL_EVENTEXEC ( eventExecRens )

static

Definition at line 371 of file heur_rens.c.

References EVENTHDLR_NAME, NULL, SCIP_CALL, SCIP_EVENTTYPE_LPSOLVED, SCIPdebugMessage, SCIPeventGetType(), SCIPeventhdlrGetName(), SCIPgetNLPs(), and SCIPinterruptSolve().

SCIP_RETCODE SCIPapplyRens	(	SCIP *	scip,
		SCIP_HEUR *	heur,
		SCIP_RESULT *	result,
		SCIP_Real	minfixingrate,
		SCIP_Real	minimprove,
		SCIP_Longint	maxnodes,
		SCIP_Longint	nstallnodes,
		char	startsol,
		SCIP_Bool	binarybounds,
		SCIP_Bool	uselprows
	)

main procedure of the RENS heuristic, creates and solves a sub-SCIP

Parameters

scip	original SCIP data structure
heur	heuristic data structure
result	result data structure
minfixingrate	minimum percentage of integer variables that have to be fixed
minimprove	factor by which RENS should at least improve the incumbent
maxnodes	maximum number of nodes for the subproblem
nstallnodes	number of stalling nodes for the subproblem
startsol	solution used for fixing values ('l'p relaxation, 'n'lp relaxation)
binarybounds	should general integers get binary bounds [floor(.),ceil(.)]?
uselprows	should subproblem be created out of the rows in the LP rows?

Definition at line 397 of file heur_rens.c.

static SCIP_DECL_HEURCOPY ( heurCopyRens )

static

copy method for primal heuristic plugins (called when SCIP copies plugins)

Definition at line 731 of file heur_rens.c.

References HEUR_NAME, NULL, and SCIPheurGetName().

static SCIP_DECL_HEURFREE ( heurFreeRens )

static

destructor of primal heuristic to free user data (called when SCIP is exiting)

Definition at line 745 of file heur_rens.c.

static SCIP_DECL_HEURINIT ( heurInitRens )

static

initialization method of primal heuristic (called after problem was transformed)

Definition at line 765 of file heur_rens.c.

static SCIP_DECL_HEUREXEC ( heurExecRens )

static

execution method of primal heuristic

Definition at line 785 of file heur_rens.c.

SCIP_RETCODE SCIPincludeHeurRens ( SCIP * scip )

creates the rens primal heuristic and includes it in SCIP

Parameters

scip	SCIP data structure

Definition at line 858 of file heur_rens.c.

Referenced by SCIPincludeDefaultPlugins().

SCIP

Detailed Description

Macros

Functions

Macro Definition Documentation

Function Documentation