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Re: [Help-glpk] initial basis

From: Andrew Makhorin
Subject: Re: [Help-glpk] initial basis
Date: Wed, 16 Sep 2009 19:39:17 +0400

> I've got a question about LP initial basis.

> I create a problem, then optimize it, and save status for variables and
> constraints, and delete the problem.
> I create a new problem, early the same as the first one : I only remove
> some variables (and so modify/remove some constraints).
> Is there a way, in this configuration, to use the statuses of the first
> optimization ? The number of basis variable in the first optimization is
> not the same as the number of rows in the second, but the basis of the
> first optimization could be usefull  for the second.

If the number of basic variables is not equal to the number of rows,
the basis is invalid and therefore cannot be used as initial basis
(at least glpk does not provide such a feature).

Rather than removing basic variables, that invalidates the basis, you
could fix them at zero; this gives the same effect, however, keeps the
basis valid.

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