Detailed Description

Constraint handler for logicor constraints $1^T x \ge 1$ (equivalent to set covering, but algorithms are suited for depth first search).

Author: Tobias Achterberg; Michael Winkler

This constraint handler handles a special type of linear constraints, namely logic or constraints. These are equivalent to set covering constraints, but are handled by special algorithms which are better suited for depth first search. For a set of binary variables $x_i, i=1,\dots,n$ , a logic or constraint has the form

$\sum_{i=1}^n x_i \ge 1.$

Definition in file cons_logicor.h.

#include "scip/scip.h"

Go to the source code of this file.

Functions
SCIP_RETCODE	SCIPincludeConshdlrLogicor (SCIP *scip)

SCIP_RETCODE	SCIPcreateConsLogicor (SCIP scip, SCIP_CONS cons, const char name, int nvars, SCIP_VAR **vars, 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	SCIPcreateConsBasicLogicor (SCIP scip, SCIP_CONS cons, const char name, int nvars, SCIP_VAR **vars)

SCIP_RETCODE	SCIPaddCoefLogicor (SCIP scip, SCIP_CONS cons, SCIP_VAR *var)

int	SCIPgetNVarsLogicor (SCIP scip, SCIP_CONS cons)

SCIP_VAR **	SCIPgetVarsLogicor (SCIP scip, SCIP_CONS cons)

SCIP_Real	SCIPgetDualsolLogicor (SCIP scip, SCIP_CONS cons)

SCIP_Real	SCIPgetDualfarkasLogicor (SCIP scip, SCIP_CONS cons)

SCIP_ROW *	SCIPgetRowLogicor (SCIP scip, SCIP_CONS cons)

Function Documentation

SCIP_RETCODE SCIPincludeConshdlrLogicor ( SCIP * scip )

creates the handler for logic or constraints and includes it in SCIP

Parameters

scip	SCIP data structure

SCIP_RETCODE SCIPcreateConsLogicor	(	SCIP *	scip,
		SCIP_CONS **	cons,
		const char *	name,
		int	nvars,
		SCIP_VAR **	vars,
		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 logic or 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
nvars	number of variables in the constraint
vars	array with variables of constraint entries
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 SCIPcreateConsBasicLogicor	(	SCIP *	scip,
		SCIP_CONS **	cons,
		const char *	name,
		int	nvars,
		SCIP_VAR **	vars
	)

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

See Also: SCIPcreateConsLogicor() 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
nvars	number of variables in the constraint
vars	array with variables of constraint entries

SCIP_RETCODE SCIPaddCoefLogicor	(	SCIP *	scip,
		SCIP_CONS *	cons,
		SCIP_VAR *	var
	)

adds coefficient in logic or constraint

Parameters

scip	SCIP data structure
cons	logicor constraint
var	variable to add to the constraint

int SCIPgetNVarsLogicor	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets number of variables in logic or constraint

Parameters

scip	SCIP data structure
cons	constraint data

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

gets array of variables in logic or constraint

Parameters

scip	SCIP data structure
cons	constraint data

SCIP_Real SCIPgetDualsolLogicor	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets the dual solution of the logic or constraint in the current LP

Parameters

scip	SCIP data structure
cons	constraint data

SCIP_Real SCIPgetDualfarkasLogicor	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets the dual Farkas value of the logic or constraint in the current infeasible LP

Parameters

scip	SCIP data structure
cons	constraint data

SCIP_ROW* SCIPgetRowLogicor	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

returns the linear relaxation of the given logic or constraint; may return NULL if no LP row was yet created; the user must not modify the row!

Parameters

scip	SCIP data structure
cons	constraint data

SCIP

Detailed Description

Functions

Function Documentation