Re: [Fwd: identifying infeasible problem without using the LP presolver]

[Michael Hennebry]

On Mon, 21 Mar 2022, Andrew Makhorin wrote:

> -------- Forwarded Message --------
> From: Will Tipton <wtipton@janestreet.com>
> To: help-glpk@gnu.org
> Cc: John Rice <jrice@janestreet.com>
> Subject: identifying infeasible problem without using the LP presolver
> Date: Mon, 21 Mar 2022 11:15:44 -0400

> > Running without the presolver usually works great. However, we can't
> > rely on the results in this case, because the simplex algorithm
> > returns an OK error code even when it fails to find a feasible
> > solution.

If the presolver is not used,
glp_simplex will return 0 iff it was able to do its job.
That includes discovering that the problem has no solution.
To get the desired information, use glp_get_status.

If the presolver is used,
glp_simplex will return 0 iff it was able to do its job
and the presolver did not determine that
the problem was primal or dual infeasible.

--
Michael   hennebry@web.cs.ndsu.NoDak.edu
Electic cars run on coal.