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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:navy">John,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:navy"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:navy">I upgraded CBC to 2.8.0 and with that version the model runs fine.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:navy"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:navy">Thanks a lot!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:navy"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:navy">Marcel<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:navy"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:navy"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"> cbc-bounces@list.coin-or.org [mailto:cbc-bounces@list.coin-or.org]
<b>On Behalf Of </b>John Forrest<br>
<b>Sent:</b> Thursday, April 18, 2013 6:10 PM<br>
<b>To:</b> cbc@list.coin-or.org<br>
<b>Subject:</b> Re: [Cbc] Switch off postsolve?<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Marcel,<br>
<br>
I can get a similar error using 2.7.5. I have also tried 2.7.8 and that was fine. I would suggest upgrading to at least 2.7.8.<br>
<br>
John Forrest<br>
On 18/04/13 11:53, Marcel Hunting wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Hi,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">I have a small MIP problem for which CBC 2.7.5 returns infeasible while the problem is in fact feasible. This is part of the log file:</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Optimal - objective value 5625.1701</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Integer solution of -5625.1701 found by feasibility pump after 0 iterations and 0 nodes (0.17 seconds)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Objective coefficients multiple of 0.1</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Search completed - best objective -5625.170085470087, took 0 iterations and 0 nodes (0.18 seconds)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Maximum depth 0, 0 variables fixed on reduced cost</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">0 Obj 5625.1701 Primal inf 2.2580657 (48)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">3 Obj 5623.2228 Primal inf 5.4953389 (94)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">…</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">40 Obj 5612.1607 Primal inf 1.3658683 (28)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Primal infeasible - objective value 5612.1607</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">The objective value (5625.1701) of the integer solution found by the feasibility pump algorithm corresponds to the objective value of the optimal solution.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">It seems that CBC does some kind of postsolve which fixes variables and that appears to be infeasible. Does CBC have a parameter to switch off the postsolve?</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">I can provide a LP or MPS file of the model. The scaling of the model seems ok.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Best regards,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Marcel Hunting</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><br>
<br>
<br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>Cbc mailing list<o:p></o:p></pre>
<pre><a href="mailto:Cbc@list.coin-or.org">Cbc@list.coin-or.org</a><o:p></o:p></pre>
<pre><a href="http://list.coin-or.org/mailman/listinfo/cbc">http://list.coin-or.org/mailman/listinfo/cbc</a><o:p></o:p></pre>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
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