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

On Mon, 21 Mar 2022, Andrew Makhorin wrote:

> -------- Forwarded Message --------
> From: Will Tipton <[email protected]>
> To: [email protected]
> Cc: John Rice <[email protected]>
> 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   [email protected]
Electic cars run on coal.