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ampl / mp

An open-source library for mathematical programming
https://mp.ampl.com
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Gurobi option InfUnbdInfo #244

Closed 4er4er4er closed 2 months ago

4er4er4er commented 2 months ago

A user is looking for Gurobi parameter InfUnbdInfo which seems to be new in version 11 but not supported yet in AMPL's gurobi_options. (I can't find it anywhere in the release notes, actually.) Is it present in some form, or can it be added?

As a workaround, I have suggested to the user to try optionnative="InfUnbdInfo 1" .

glebbelov commented 2 months ago

InfUnbdInfo=1 is set automatically whenever alg:rays is non-zero, with alg:rays described as follows:

alg:rays (rays)
      Whether to return suffix .unbdd if the objective is unbounded or suffix
      .dunbdd if the constraints are infeasible:

      0 - Neither
      1 - Just .unbdd
      2 - Just .dunbdd
      3 - Both (default)

And these suffixes are all what InfUnbdInfo is good for. (We can add text saying that .dunbdd is the Farkas dual.)

We can add a synonym option alg:infunbdinfo, which when set to 1, would mean alg:rays=3 for example.