Detailed Description

constraint handler for linking binary variables to an integer variable

Author: Stefan Heinz; Jens Schulz

The constraints handler stores linking constraints between an integer variable and an array of binary variables. Such a linking constraint has the form:

$y = \sum_{i=1}^n {c_i * x_i}$

with integer variable $ y $ , binary variables $x_1, \dots, x_n$ and offset $b \in Q$ , and with the additional side condition that exactly one binary variable has to be one (set partitioning condition).

This constraint can be created only with the integer variable. In this case the binary variables are only created on demand. That is, whenever someone asks for the binary variables. Therefore, such constraints can be used to get a "binary representation" of the domain of the integer variable which will be dynamically created.

Definition in file cons_linking.h.

#include "scip/scip.h"

Go to the source code of this file.

Functions
SCIP_RETCODE	SCIPincludeConshdlrLinking (SCIP *scip)

SCIP_RETCODE	SCIPcreateConsLinking (SCIP scip, SCIP_CONS cons, const char name, SCIP_VAR intvar, SCIP_VAR binvars, int vals, int nbinvars, SCIP_Bool initial, SCIP_Bool separate, SCIP_Bool enforce, SCIP_Bool check, SCIP_Bool propagate, SCIP_Bool local, SCIP_Bool modifiable, SCIP_Bool dynamic, SCIP_Bool removable, SCIP_Bool stickingatnode)

SCIP_RETCODE	SCIPcreateConsBasicLinking (SCIP scip, SCIP_CONS cons, const char name, SCIP_VAR intvar, SCIP_VAR binvars, int vals, int nbinvars)

SCIP_Bool	SCIPexistsConsLinking (SCIP scip, SCIP_VAR intvar)

SCIP_CONS *	SCIPgetConsLinking (SCIP scip, SCIP_VAR intvar)

SCIP_VAR *	SCIPgetIntvarLinking (SCIP scip, SCIP_CONS cons)

SCIP_RETCODE	SCIPgetBinvarsLinking (SCIP scip, SCIP_CONS cons, SCIP_VAR **binvars, int nbinvars)

int	SCIPgetNBinvarsLinking (SCIP scip, SCIP_CONS cons)

int *	SCIPgetValsLinking (SCIP scip, SCIP_CONS cons)

Function Documentation

SCIP_RETCODE SCIPincludeConshdlrLinking ( SCIP * scip )

creates the handler for linking constraints and includes it in SCIP

Parameters

scip	SCIP data structure

SCIP_RETCODE SCIPcreateConsLinking	(	SCIP *	scip,
		SCIP_CONS **	cons,
		const char *	name,
		SCIP_VAR *	intvar,
		SCIP_VAR **	binvars,
		int *	vals,
		int	nbinvars,
		SCIP_Bool	initial,
		SCIP_Bool	separate,
		SCIP_Bool	enforce,
		SCIP_Bool	check,
		SCIP_Bool	propagate,
		SCIP_Bool	local,
		SCIP_Bool	modifiable,
		SCIP_Bool	dynamic,
		SCIP_Bool	removable,
		SCIP_Bool	stickingatnode
	)

creates and captures a linking constraint

Note: the constraint gets captured, hence at one point you have to release it using the method SCIPreleaseCons()

Parameters

scip	SCIP data structure
cons	pointer to hold the created constraint
name	name of constraint
intvar	integer variable which should be linked
binvars	binary variables
vals	coefficients of the binary variables
nbinvars	number of binary starting variables
initial	should the LP relaxation of constraint be in the initial LP? Usually set to TRUE. Set to FALSE for 'lazy constraints'.
separate	should the constraint be separated during LP processing? Usually set to TRUE.
enforce	should the constraint be enforced during node processing? TRUE for model constraints, FALSE for additional, redundant constraints.
check	should the constraint be checked for feasibility? TRUE for model constraints, FALSE for additional, redundant constraints.
propagate	should the constraint be propagated during node processing? Usually set to TRUE.
local	is constraint only valid locally? Usually set to FALSE. Has to be set to TRUE, e.g., for branching constraints.
modifiable	is constraint modifiable (subject to column generation)? Usually set to FALSE. In column generation applications, set to TRUE if pricing adds coefficients to this constraint.
dynamic	is constraint subject to aging? Usually set to FALSE. Set to TRUE for own cuts which are separated as constraints.
removable	should the relaxation be removed from the LP due to aging or cleanup? Usually set to FALSE. Set to TRUE for 'lazy constraints' and 'user cuts'.
stickingatnode	should the constraint always be kept at the node where it was added, even if it may be moved to a more global node? Usually set to FALSE. Set to TRUE to for constraints that represent node data.

SCIP_RETCODE SCIPcreateConsBasicLinking	(	SCIP *	scip,
		SCIP_CONS **	cons,
		const char *	name,
		SCIP_VAR *	intvar,
		SCIP_VAR **	binvars,
		int *	vals,
		int	nbinvars
	)

creates and captures a linking constraint in its most basic version, i. e., all constraint flags are set to their basic value as explained for the method SCIPcreateConsLinking(); all flags can be set via SCIPsetConsFLAGNAME-methods in scip.h

See also: SCIPcreateConsLinking() for information about the basic constraint flag configuration

Note: the constraint gets captured, hence at one point you have to release it using the method SCIPreleaseCons()

Parameters

scip	SCIP data structure
cons	pointer to hold the created constraint
name	name of constraint
intvar	integer variable which should be linked
binvars	binary variables, or NULL
vals	coefficients of the binary variables
nbinvars	number of binary variables

SCIP_Bool SCIPexistsConsLinking	(	SCIP *	scip,
		SCIP_VAR *	intvar
	)

checks if for the given integer variable a linking constraint exists

Parameters

scip	SCIP data structure
intvar	integer variable which should be linked

SCIP_CONS* SCIPgetConsLinking	(	SCIP *	scip,
		SCIP_VAR *	intvar
	)

returns the linking constraint belonging the given integer variable or NULL if it does not exist yet

Parameters

scip	SCIP data structure
intvar	integer variable which should be linked

SCIP_VAR* SCIPgetIntvarLinking	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

returns the integer variable of the linking constraint

Parameters

scip	SCIP data structure
cons	linking constraint

SCIP_RETCODE SCIPgetBinvarsLinking	(	SCIP *	scip,
		SCIP_CONS *	cons,
		SCIP_VAR ***	binvars,
		int *	nbinvars
	)

returns the binary variables of the linking constraint

Parameters

scip	SCIP data structure
cons	linking constraint
binvars	pointer to store the binary variables array pointer
nbinvars	pointer to store the number of returned binary variables

int SCIPgetNBinvarsLinking	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

returns the number of binary variables of the linking constraint

Parameters

scip	SCIP data structure
cons	linking constraint

int* SCIPgetValsLinking	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

returns the coefficients of the binary variables

Parameters

scip	SCIP data structure
cons	linking constraint

SCIP

Detailed Description

Functions

Function Documentation