[Cgl] CglTwomir issue (Re: Success!)

[Watson, Jean-paul]

Hi Robin,

It is still a bug; I'll post it now.

Jean-Paul

From: Robin Lougee-Heimer [mailto:robinlh at us.ibm.com]
Sent: Thursday, December 10, 2009 12:31 PM
To: Watson, Jean-paul
Cc: cgl at list.coin-or.org; gunluk at us.ibm.com
Subject: CglTwomir issue (Re: [Cgl] Success!)


Jean-Paul:

If this is still an issue, can you post it in the Cgl bug tracking facility?  https://projects.coin-or.org/Cgl/report.  The Project Manager for CglTwomir is Oktay Gunluk.

thanks,
Robin

I have isolated a situation in which I believe CglTwomir is returning invalid cuts. I have attached a test driver (driver.cpp), a test input file (mas74.mps, from miplib2003), and the output trace I obtain on our rather vanilla RedHat linux server.


The "catch" is that I'm using CPLEX 11.2, and the OsiCpxSolverInterface. Although this technically shouldn't matter, I suppose (the behavior also occurs with other versions of CPLEX).

A quick summary of the unexpected behavior:
1)      The LP relaxation for mas74 solves fine - relaxation is around 10K. Validated with various other solvers.
2)      3 two-mir cuts are found and successfully applied.
3)      Upon re-solve after cut addition, the LP relaxation is something like 21K, which is far above the integer optimal of ~11K. Obviously incorrect behavior.

Any help is greatly appreciated - I am seeing similar behavior on a handful of other test instances.





----------------------------------------------------------------------------------
Robin Lougee-Heimer, PhD
Program Manager, COIN-OR
IBM TJ Watson Research Center
1101 Kitchawan Road, Yorktown Heights, NY 10598
ph: 914-945-3032   fax: 914-945-3434
robinlh at us.ibm.com
http://www.coin-or.org



"Watson, Jean-paul" <jwatson at sandia.gov>
Sent by: cgl-bounces at list.coin-or.org

10/06/2009 11:21 PM

To

"Matthew Saltzman" <mjs at clemson.edu>

cc

"cgl at list.coin-or.org" <cgl at list.coin-or.org>

Subject

Re: [Cgl] Success!







That was probably it - the total was around 80K bytes (mas74 is largely than I thought). I've attached g'zipped versions of the attachments.

Jean-Paul

--


Dr. Jean-Paul Watson
Discrete Math and Complex Systems Department
Sandia National Laboratories
P.O. Box 5800, MS 1318
Albuquerque, NM 87185-1318
(505) 845-8887
jwatson at sandia.gov




-----Original Message-----
From: Matthew Saltzman [mailto:mjs at clemson.edu]
Sent: Tuesday, October 06, 2009 8:48 PM
To: Watson, Jean-paul
Cc: cgl at list.coin-or.org
Subject: Re: [Cgl] Success!

How big are your attachments?  They should work, but there's a 40K limit
on message body size.

On Tue, 2009-10-06 at 20:33 -0600, Watson, Jean-paul wrote:
> Sorry about the posting issues - I'm not sure why the attachments
> didn't come through. If someone is able to look at this bug, please
> contact me (I'm not sure who is the CGL Czar) and I'll forward them
> along.
>
> Jean-Paul


--
               Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs

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