How to delete constraints and variables?! - Xpress-MP

Message from discussion How to delete constraints and variables?!

Chris Oakley

More options 30 Apr 2008, 12:03

From: "Chris Oakley" <chris.oak...@dashoptimization.com>

Date: Wed, 30 Apr 2008 12:03:39 +0100

Local: Wed 30 Apr 2008 12:03

Subject: RE: How to delete constraints and variables?!

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The basic rule is: a variable is automatically deleted when it is no longer
referenced (e.g. local variable of a subroutine or deleted from a dynamic
array using
'delcell') _and_ does not appear in any constraint (note that bounds and
is_* are constraints). Similarly, a constraint is deleted if it is no longer
referenced and is empty (to clear a constraint give it the value 0:
myctr:=0).

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> -----Original Message-----
> From: xpressmp@googlegroups.com [mailto:xpressmp@googlegroups.com] On
> Behalf Of cees
> Sent: 30 April 2008 12:01
> To: Xpress-MP
> Subject: Re: How to delete constraints and variables?!

> Generally spoken: How do I delete already declared variables and free
> related memory? How can I provide a garbage collection manually?

> On 28 Apr., 22:25, cees <tstra...@gmail.com> wrote:
> > Hi! My optimization model is extended stepwise, that is, it is set-up
> > and solved for a specific planning horizon and extended afterwards to
> > cover more periods. This is done to simulate a rolling horizon
> > environment. Therefore, in each simultion run the optimization model
> > is extended with new constraints and variables. Only in under special
> > circumstance some already inialized constraints in variable are
> > superfluous. I would like to delete these not needed constraints and
> > variables, because for large simulation instances the model exceeds
> > the available RAM of my computer and Xpress terminates. There are a
> > lot of not needed constraints, because preprocessing always reduces
> > the problem size strongly.

> > How do I delete constraints and variables? Does a corresponding
> > function to "create" exist? Or could I use "sethidden"? I could image
> > that the latter doesn't help to reduce memory usage...

> > Thanks a lot!

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