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<p>John,</p>
<p> I also got that solution after two hours while activating some of the cuts and heuristics that are off by default. Can you tell me what you tried related with symmetry? Apparently you got the same solution must faster. After getting that solution, I left it to run for a day and it didn't got any better (not closing the gap). The best solution is a little above 284000 if I remember correctly, so we are not that far away from the optimum.</p>
<p> Regarding the presolver, I may be able to integrate that "process" (presolving, exporting and presolving again) calling CBC several times while solving our problem, if that helps. I'll make some tests.</p>
<p>Haroldo,</p>
<p> I could get a valid solution after some minutes, even with the default parameters and activating some of the heuristics and additional cuts helped getting better solutions faster. The manual you linked is useful, obrigado.</p>
<p> Best regards,</p>
<p>Rui Patrocínio</p>
<p>A 2019-11-23 10:00, John Forrest escreveu:</p>
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<div class="pre" style="margin: 0; padding: 0; font-family: monospace">My guess is that Cbc is very bad at handling symmetry. There is a lot of symmetry and trying some of the ways that Cbc can deal with symmetry I can get a solution of 296773 fairly quickly, but after an hour it does not seem to be closing the gap. The other area where Cbc is failing somewhat is preprocessing - if I export the model several times (each time doing presolve) then I can make it smaller - this obviously wrong.<br /> <br /> <span style="white-space: nowrap;">John Forrest</span><br /> <br /> <span style="white-space: nowrap;">On 22/11/2019 15:44, Rui Patrocínio wrote:</span>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0"><span style="white-space: nowrap;">Hi,</span><br /> <br /> I'm trying to solve one instance of a problem that is taking a long time to obtain a good solution. Since all variables are binary, probing and implication cuts are doing some work and RINS and Vnd are apparently also improving solutions. For other instances of the problem we are solving, CBC has an acceptable performance but for this instance apparently there's something going wrong (~20 seconds to get the optimum solution with a commercial solver versus never getting the optimum solution with CBC).<br /> <br /> If someone can take a look at the model and give me a hint of what is going on, I would appreciate it.<br /> <br /> The model is at <a href="https://drive.google.com/open?id=1bd4jWONmoyAKIi0oLa-AU-ZTu7_8qhb6" target="_blank" rel="noopener noreferrer">https://drive.google.com/open?id=1bd4jWONmoyAKIi0oLa-AU-ZTu7_8qhb6</a><br /> <br /> -- SISCOG - Sistemas Cognitivos, SA<br /> <br /> <span style="white-space: nowrap;">*Rui Patrocínio*</span><br /> <br /> _______________________________________________<br /> <span style="white-space: nowrap;">Cbc mailing list</span><br /> <span style="white-space: nowrap;"><a href="mailto:Cbc@list.coin-or.org">Cbc@list.coin-or.org</a></span><br /> <span style="white-space: nowrap;"><a href="https://list.coin-or.org/mailman/listinfo/cbc" target="_blank" rel="noopener noreferrer">https://list.coin-or.org/mailman/listinfo/cbc</a></span><br /> </blockquote>
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