[Cbc] Cbc CLI Infeasible Error

[Matthew Gidden]

Hi all,

I've been posting a lot recently.. first of all, thank you for replying!

I've unit tested my application pretty vigorously, and a Cbc API unit test
broke when I moved to the CLI implementation. Specifically, I set up the
following toy problem:

min 2x + 0.5y + 1.8z
st     x  +     y            > 4.4
                   y +     z  < 3.1
x in [1.3, 5], y in [1.7, 5], z in [0.4, 5]
y, z integer

The unit test originally passed using the OsiCbcSolverInterface's initial
solve and branch and bound methods. I updated it to use an
OsiClpSolverInterface that is fed a CbcModel and call CbcMain0/1 on said
model. The unit test now fails with the following relevant output:

> Welcome to the CBC MILP Solver
> Version: 2.8.7
> Build Date: Dec 28 2013
> command line - exchng -solve -quit (default strategy 1)
> Continuous objective value is 5.47 - 0.00 seconds
> Cgl0000I Cut generators found to be infeasible! (or unbounded)
> Pre-processing says infeasible or unbounded


To double check that indeed a feasible solution existed, I solved the
maximization form of the same instance. Attached are MPS files for the max
and min forms, and I have verified the same behavior using the cbc CLI
(i.e., min is returned as infeasible and max solves).

I'm curious if anyone can replicate this and/or has any advice.

Cheers,

-- 
Matthew Gidden
Ph.D. Candidate, Nuclear Engineering
The University of Wisconsin -- Madison
Ph. 225.892.3192
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.coin-or.org/pipermail/cbc/attachments/20140730/2166d95c/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: min.mps
Type: application/x-mps
Size: 597 bytes
Desc: not available
URL: <http://list.coin-or.org/pipermail/cbc/attachments/20140730/2166d95c/attachment.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: max.mps
Type: application/x-mps
Size: 597 bytes
Desc: not available
URL: <http://list.coin-or.org/pipermail/cbc/attachments/20140730/2166d95c/attachment-0001.bin>