Scippy

SCIP

Solving Constraint Integer Programs

presol_dualagg.h File Reference

Detailed Description

aggregate variables by dual arguments

Author
Dieter Weninger

This presolver looks for variables which could not be handled by duality fixing because of one up-/downlock. If the constraint which delivers the up-/downlock has a specific structure, we can aggregate the corresponding variable.

In more detail (for a minimization problem and the case of only one uplock):

Given a variable x_i with c_i <= 0 and only one up lock (originating from a constraint c), we are looking for a binary variable x_j such that: 1) if x_j = 0, constraint c can only be fulfilled for x_i = lb_i, and 2) if x_j = 1, constraint c becomes redundant and x_i can be dual-fixed to its upper bound ub_i (or vice versa). Then we can perform the following aggregation: x_i = lb_i + x_j (ub_i - lb_i).

Similar arguments apply for the case of only one down lock and c_i >= 0.

Definition in file presol_dualagg.h.

#include "scip/scip.h"

Go to the source code of this file.

Functions

SCIP_RETCODE SCIPincludePresolDualagg (SCIP *scip)
 

Function Documentation

SCIP_RETCODE SCIPincludePresolDualagg ( SCIP scip)

creates the dualagg presolver and includes it in SCIP

Parameters
scipSCIP data structure