<div dir="ltr">Hi Yves,<div>did you try the CglGMI generator? You may want to see if using CglGMI instead of CglGomory helps. In my experience, the cuts from CglGMI are less prone to numerical errors: in fact, that's the reason the generator was developed. See <a href="http://link.springer.com/article/10.1007%2Fs12532-013-0057-4">http://link.springer.com/article/10.1007%2Fs12532-013-0057-4</a></div><div><br></div><div>Giacomo</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Mar 4, 2015 at 7:06 PM, Yves Touchard <span dir="ltr"><<a href="mailto:ytouch@dxo.com" target="_blank">ytouch@dxo.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<small>Hello,<br>
<br>
Switching off the twomir cuts makes also the problem feasible.<br>
<br>
Cheers<span class="HOEnZb"><font color="#888888"><br>
<br>
Yves<br>
</font></span></small><br>
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<th align="RIGHT" nowrap valign="BASELINE">Sujet : </th>
<td>Gomory or not Gomory, that is the question.</td>
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<th align="RIGHT" nowrap valign="BASELINE">Date : </th>
<td>Tue, 03 Mar 2015 20:03:03 +0100</td>
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<th align="RIGHT" nowrap valign="BASELINE">De : </th>
<td>Yves Touchard <a href="mailto:yves.touchard@sfr.fr" target="_blank">
<yves.touchard@sfr.fr></a></td>
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<th align="RIGHT" nowrap valign="BASELINE">Pour : </th>
<td><a href="mailto:cbc@list.coin-or.org" target="_blank">cbc@list.coin-or.org</a></td>
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<br>
<br>
</span><div><div class="h5"><font size="-1">Hello,<br>
<br>
You will find here (</font><font size="-1"><font size="-1"><a href="https://www.dropbox.com/s/ayo93hi4togpc9m/noGom.lp?dl=0" target="_blank">https://www.dropbox.com/s/ayo93hi4togpc9m/noGom.lp?dl=0</a></font>) a constraint
file for which cbc founds a solution when Gomory cuts are removed or for specific cutlength values.<br>
<br>
In other words, the following command leads to an infeasible problem:<br>
<i>/soft/cbc-trunk-2149/bin/cbc noGom.lp branch printingOptions normal solution noGom.sol</i><br>
<br>
and with the following commands, cbc claims that there is a solution:<br>
</font><font size="-1"><font size="-1"><i>/soft/cbc-trunk-2149/bin/cbc noGom.lp gomory off branch printingOptions normal solution noGom.sol</i></font><br>
</font><font size="-1"><font size="-1"><i>/soft/cbc-trunk-2149/bin/cbc noGom.lp cutlength xx branch printingOptions normal solution noGom.sol</i></font> (with xx equal to -1, 0, 10, 20... and different from 30...)<br>
<br>
Since our problems are dynamically generated, it is very painful to try to solve them with different options, hoping that the right set is in the list.<br>
<br>
</font><font size="-1">So, is there a way to find this set of options.<br>
Or could you explain what are the rows that are difficult for cbc.<br>
And, does the change of the continuous variables into integer variables help? (for our problems, it makes sense).<br>
<br>
Thanks and regards<br>
<br>
Yves<br>
</font><br>
</div></div></div>
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