XPRSiisisolations
XPRSiisisolations |
Purpose
Performs the isolation identification procedure for an Irreducible Infeasible Set (IIS).
Synopsis
int XPRS_CC XPRSiisisolations(XPRSprob prob, int num);
Arguments
|
prob
|
The current problem.
|
|
num
|
The number of the IIS identified by either
XPRSiisfirst (
IIS),
XPRSiisnext (
IIS
-n) or
XPRSiisall (
IIS
-a) in which the isolations should be identified.
|
Example
This example finds the first IIS and searches for the isolations in that IIS.
XPRSiisfirst(prob,1,&status); XPRSiisisolations (prob,1);
Further information
2. An IIS isolation is a special constraint or bound in an IIS. Removing an IIS isolation constraint or bound will remove all infeasibilities in the IIS without increasing the infeasibilities in any row or column outside the IIS, thus in any other IISs. The IIS isolations thus indicate the likely cause of each independent infeasibility and give an indication of which constraint or bound to drop or modify. It is not always possible to find IIS isolations.
3. Generally, one should first look for rows or columns in the IIS which are both in isolation, and have a high dual multiplier relative to the others.
4. The
num parameter cannot be zero: the concept of isolations is meaningless for the initial infeasible subproblem.
Related topics
XPRSgetiisdata,
XPRSiisall,
XPRSiisclear,
XPRSiisfirst,
XPRSiisnext,
XPRSiisstatus,
XPRSiiswrite,
IIS.