Detailed Description

constraint handler that checks bounds on fixed variables

Author: Stefan Vigerske

For each original variable that has a counterpart in the transformed problem which is not active (i.e., fixed, negated, aggregated, or multiaggregated), check the original bounds. In enforcement, add a cut that enforces the bounds or tighten LP feasibility tolerance.

Definition in file cons_fixedvar.c.

#include <assert.h>
#include "scip/cons_fixedvar.h"

Go to the source code of this file.

Macros
#define	CONSHDLR_NAME "fixedvar"

#define	CONSHDLR_DESC "check bounds of original variables that are not active in transformed problem"

#define	CONSHDLR_ENFOPRIORITY -7000000

#define	CONSHDLR_CHECKPRIORITY -7000000

#define	CONSHDLR_EAGERFREQ -1

#define	CONSHDLR_NEEDSCONS FALSE

#define	DEFAULT_ENABLED TRUE

#define	DEFAULT_SUBSCIPS TRUE

#define	DEFAULT_PREFERCUT TRUE

#define	assertSmallViolation(lb, val, ub) (assert((val) >= (lb) - 0.5 && (val) <= (ub) + 0.5));

Functions
static SCIP_RETCODE	addCut (SCIP scip, SCIP_CONSHDLR conshdlr, SCIP_SOL sol, SCIP_VAR var, SCIP_Bool success, SCIP_Bool cutoff)

static	SCIP_DECL_CONSHDLRCOPY (conshdlrCopyFixedvar)

static	SCIP_DECL_CONSFREE (consFreeFixedvar)

static	SCIP_DECL_CONSINITSOL (consInitsolFixedvar)

static	SCIP_DECL_CONSEXITSOL (consExitsolFixedvar)

static	SCIP_DECL_CONSENFOLP (consEnfolpFixedvar)

static	SCIP_DECL_CONSENFORELAX (consEnforelaxFixedvar)

static	SCIP_DECL_CONSENFOPS (consEnfopsFixedvar)

static	SCIP_DECL_CONSCHECK (consCheckFixedvar)

static	SCIP_DECL_CONSLOCK (consLockFixedvar)

SCIP_RETCODE	SCIPincludeConshdlrFixedvar (SCIP *scip)

Macro Definition Documentation

◆ CONSHDLR_NAME

#define CONSHDLR_NAME "fixedvar"

Definition at line 44 of file cons_fixedvar.c.

Referenced by SCIP_DECL_CONSHDLRCOPY(), and SCIPincludeConshdlrFixedvar().

◆ CONSHDLR_DESC

#define CONSHDLR_DESC "check bounds of original variables that are not active in transformed problem"

Definition at line 45 of file cons_fixedvar.c.

Referenced by SCIPincludeConshdlrFixedvar().

◆ CONSHDLR_ENFOPRIORITY

#define CONSHDLR_ENFOPRIORITY -7000000

priority of the constraint handler for constraint enforcing

Definition at line 46 of file cons_fixedvar.c.

Referenced by SCIPincludeConshdlrFixedvar().

◆ CONSHDLR_CHECKPRIORITY

#define CONSHDLR_CHECKPRIORITY -7000000

priority of the constraint handler for checking feasibility

Definition at line 47 of file cons_fixedvar.c.

Referenced by SCIPincludeConshdlrFixedvar().

◆ CONSHDLR_EAGERFREQ

#define CONSHDLR_EAGERFREQ -1

frequency for using all instead of only the useful constraints in separation, propagation and enforcement, -1 for no eager evaluations, 0 for first only

Definition at line 48 of file cons_fixedvar.c.

Referenced by SCIPincludeConshdlrFixedvar().

◆ CONSHDLR_NEEDSCONS

#define CONSHDLR_NEEDSCONS FALSE

should the constraint handler be skipped, if no constraints are available?

Definition at line 51 of file cons_fixedvar.c.

Referenced by SCIPincludeConshdlrFixedvar().

◆ DEFAULT_ENABLED

#define DEFAULT_ENABLED TRUE

enable constraint handler

Definition at line 54 of file cons_fixedvar.c.

Referenced by SCIPincludeConshdlrFixedvar().

◆ DEFAULT_SUBSCIPS

#define DEFAULT_SUBSCIPS TRUE

also run in subSCIPs

Definition at line 55 of file cons_fixedvar.c.

Referenced by SCIPincludeConshdlrFixedvar().

◆ DEFAULT_PREFERCUT

#define DEFAULT_PREFERCUT TRUE

whether to prefer separation over tightening LP feastol in enforcement

Definition at line 56 of file cons_fixedvar.c.

Referenced by SCIPincludeConshdlrFixedvar().

◆ assertSmallViolation

#define assertSmallViolation	(	lb,
		val,
		ub
	)	(assert((val) >= (lb) - 0.5 && (val) <= (ub) + 0.5));

an assert for checking that the violation is not so large

The idea of this constraint handler is the handling of tiny bound violations that are scaled up above the feasibility tolerance by aggregation factors. Usually, the violation should still be rather "small". For this test, we quantify "small" as 0.5.

Definition at line 85 of file cons_fixedvar.c.

Referenced by SCIP_DECL_CONSCHECK(), SCIP_DECL_CONSENFOLP(), SCIP_DECL_CONSENFOPS(), and SCIP_DECL_CONSENFORELAX().

Function Documentation

◆ addCut()

static SCIP_RETCODE addCut	(	SCIP *	scip,
		SCIP_CONSHDLR *	conshdlr,
		SCIP_SOL *	sol,
		SCIP_VAR *	var,
		SCIP_Bool *	success,
		SCIP_Bool *	cutoff
	)

static

add cut to enforce global bounds on variable aggregation

Given an original fixed variable x, add cut lb <= x <= ub. SCIP will replace x by the corresponding aggregation of x in the transformed problem. Though we only need to enforce original bounds on x, we use here the global bounds on x for lb/ub, as these should be as tight as or tighter than the original bounds.

Parameters

scip	SCIP data structure
conshdlr	fixedvar conshdlr
sol	solution that is enforced
var	fixed original variable which bound is violated
success	buffer to store whether cut was added
cutoff	buffer to store whether a cutoff was detected