Detailed Description

Constraint handler for variable bound constraints $lhs \leq x + c y \leq rhs$ .

Author: Tobias Achterberg; Timo Berthold; Michael Winkler; Gerald Gamrath; Stefan Heinz

This constraint handler handles a special type of linear constraints, namely variable bound constraints. A variable bound constraint has the form

$lhs \leq x + c y \leq rhs$

with coefficient $c \in Q$ , $lhs\in Q \cup \{-\infty\}$ , $rhs\in Q \cup \{\infty\}$ , and decision variables $x$ (non-binary) and $y$ (binary or integer).

Definition in file cons_varbound.h.

#include "scip/scip.h"

Go to the source code of this file.

Functions
SCIP_RETCODE	SCIPincludeConshdlrVarbound (SCIP *scip)

SCIP_RETCODE	SCIPcreateConsVarbound (SCIP scip, SCIP_CONS cons, const char name, SCIP_VAR var, SCIP_VAR vbdvar, SCIP_Real vbdcoef, SCIP_Real lhs, SCIP_Real rhs, 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	SCIPcreateConsBasicVarbound (SCIP scip, SCIP_CONS cons, const char name, SCIP_VAR var, SCIP_VAR vbdvar, SCIP_Real vbdcoef, SCIP_Real lhs, SCIP_Real rhs)

SCIP_Real	SCIPgetLhsVarbound (SCIP scip, SCIP_CONS cons)

SCIP_Real	SCIPgetRhsVarbound (SCIP scip, SCIP_CONS cons)

SCIP_VAR *	SCIPgetVarVarbound (SCIP scip, SCIP_CONS cons)

SCIP_VAR *	SCIPgetVbdvarVarbound (SCIP scip, SCIP_CONS cons)

SCIP_Real	SCIPgetVbdcoefVarbound (SCIP scip, SCIP_CONS cons)

SCIP_Real	SCIPgetDualsolVarbound (SCIP scip, SCIP_CONS cons)

SCIP_Real	SCIPgetDualfarkasVarbound (SCIP scip, SCIP_CONS cons)

SCIP_ROW *	SCIPgetRowVarbound (SCIP scip, SCIP_CONS cons)

Function Documentation

SCIP_RETCODE SCIPincludeConshdlrVarbound ( SCIP * scip )

creates the handler for variable bound constraints and includes it in SCIP

Parameters

scip	SCIP data structure

SCIP_RETCODE SCIPcreateConsVarbound	(	SCIP *	scip,
		SCIP_CONS **	cons,
		const char *	name,
		SCIP_VAR *	var,
		SCIP_VAR *	vbdvar,
		SCIP_Real	vbdcoef,
		SCIP_Real	lhs,
		SCIP_Real	rhs,
		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 variable bound constraint: lhs <= x + c*y <= rhs

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
var	variable x that has variable bound
vbdvar	binary, integer or implicit integer bounding variable y
vbdcoef	coefficient c of bounding variable y
lhs	left hand side of variable bound inequality
rhs	right hand side of variable bound inequality
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 SCIPcreateConsBasicVarbound	(	SCIP *	scip,
		SCIP_CONS **	cons,
		const char *	name,
		SCIP_VAR *	var,
		SCIP_VAR *	vbdvar,
		SCIP_Real	vbdcoef,
		SCIP_Real	lhs,
		SCIP_Real	rhs
	)

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

See also: SCIPcreateConsVarbound() 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
var	variable x that has variable bound
vbdvar	binary, integer or implicit integer bounding variable y
vbdcoef	coefficient c of bounding variable y
lhs	left hand side of variable bound inequality
rhs	right hand side of variable bound inequality

SCIP_Real SCIPgetLhsVarbound	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets left hand side of variable bound constraint lhs <= x + c*y <= rhs

Parameters

scip	SCIP data structure
cons	constraint data

SCIP_Real SCIPgetRhsVarbound	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets right hand side of variable bound constraint lhs <= x + c*y <= rhs

Parameters

scip	SCIP data structure
cons	constraint data

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

gets bounded variable x of variable bound constraint lhs <= x + c*y <= rhs

Parameters

scip	SCIP data structure
cons	constraint data

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

gets bounding variable y of variable bound constraint lhs <= x + c*y <= rhs

Parameters

scip	SCIP data structure
cons	constraint data

SCIP_Real SCIPgetVbdcoefVarbound	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets bound coefficient c of variable bound constraint lhs <= x + c*y <= rhs

Parameters

scip	SCIP data structure
cons	constraint data

SCIP_Real SCIPgetDualsolVarbound	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets the dual solution of the variable bound constraint in the current LP

Parameters

scip	SCIP data structure
cons	constraint data

SCIP_Real SCIPgetDualfarkasVarbound	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets the dual Farkas value of the variable bound constraint in the current infeasible LP

Parameters

scip	SCIP data structure
cons	constraint data

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

returns the linear relaxation of the given variable bound 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