[Cbc] cbc solver

[Liu, Lu]

Thanks Ted.

I attached my MPS file. p.s. I also attached the same problem in LP format. Thanks!

Regards,
Lu

From: Ted Ralphs [mailto:ted at lehigh.edu]
Sent: Wednesday, March 08, 2017 3:01 PM
To: Liu, Lu <Lu.Liu at fisglobal.com>
Cc: cbc at list.coin-or.org
Subject: Re: [Cbc] cbc solver

If you post the MPS file, I'm sure someone will be able to help.
Ted

On Wed, Mar 8, 2017 at 7:53 PM, Liu, Lu <Lu.Liu at fisglobal.com<mailto:Lu.Liu at fisglobal.com>> wrote:
Hi,

I created a MPS file for my problem and I have tried CBC solver via the command line and also CPLEX via an online solver. CBC returned “ problem is unbounded” error, but CPLEX is able to give me a solution and the solution obeys the constraints. I wonder if this is a limitation of CBC. In addition, in the CBC command window, I also found that it says:

Problem SOLVER_TEST has 26 rows, 32 columns and 118 elements

but in my problem, I only have 25 columns, I find this suspicious. Could it be my MPS file formatting problem which leads the solver to think there are 32 variables? When I tweak the objective function and tried to make it bound, I got a solution like below:
X1
X2
X2
X3
X3
…
X8
X8
X9
X10

Clearly it seems to treat some of my variables as duplicates, can someone help? Thanks!
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Dr. Ted Ralphs
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Professor, Lehigh University
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