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<div><font color="#1F497D">Trying again, this time w/o attachments. Attachments seem to be bouncing.</font></div>
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<div><font color="#1F497D">Jean-Paul</font></div>
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<div><font color="#1F497D">--</font></div>
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<div><font color="#1F497D">Dr. Jean-Paul Watson</font></div>
<div><font color="#1F497D">Discrete Math and Complex Systems Department</font></div>
<div><font color="#1F497D">Sandia National Laboratories</font></div>
<div><font color="#1F497D">P.O. Box 5800, MS 1318</font></div>
<div><font color="#1F497D">Albuquerque, NM 87185-1318</font></div>
<div><font color="#1F497D">(505) 845-8887</font></div>
<div><font color="#1F497D">jwatson@sandia.gov</font></div>
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<div><font face="Tahoma, sans-serif" size="2">_____________________________________________<br>
<b>From:</b> Watson, Jean-paul <br>
<b>Sent:</b> Tuesday, October 06, 2009 4:57 PM<br>
<b>To:</b> cgl@list.coin-or.org<br>
<b>Cc:</b> Phillips, Cynthia A; Watson, Jean-paul<br>
<b>Subject:</b> Potential error in CglTwomir</font></div>
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<div><font face="Calibri, sans-serif">Hi,</font></div>
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<div><font face="Calibri, sans-serif">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. </font></div>
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<div><font face="Calibri, sans-serif">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).</font></div>
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<div><font face="Calibri, sans-serif">A quick summary of the unexpected behavior:</font></div>
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<li>The LP relaxation for mas74 solves fine – relaxation is around 10K. Validated with various other solvers.</li><li>3 two-mir cuts are found and successfully applied.</li><li>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.</li></font>
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<div><font face="Calibri, sans-serif">Any help is greatly appreciated – I am seeing similar behavior on a handful of other test instances.</font></div>
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<div><font face="Calibri, sans-serif">Thanks!</font></div>
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<div><font face="Calibri, sans-serif">Jean-Paul</font></div>
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<div><font face="Calibri, sans-serif">--</font></div>
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<div><font face="Calibri, sans-serif">Dr. Jean-Paul Watson</font></div>
<div><font face="Calibri, sans-serif">Discrete Math and Complex Systems Department</font></div>
<div><font face="Calibri, sans-serif">Sandia National Laboratories</font></div>
<div><font face="Calibri, sans-serif">P.O. Box 5800, MS 1318</font></div>
<div><font face="Calibri, sans-serif">Albuquerque, NM 87185-1318</font></div>
<div><font face="Calibri, sans-serif">(505) 845-8887</font></div>
<div><font face="Calibri, sans-serif">jwatson@sandia.gov</font></div>
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