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Hi Diego,<br>
<br>
sorry for the late response we were quite busy during the last
weeks. <br>
<br>
Yes, you can use your own separator if you know how the generated
cuts affect your pricing problem(s). If you can express your cuts
only with original variables then this does not influence the
pricing problem(s) and adding your own separator should be easy. If
your cuts depend on the reformulated variables things get
complicated. If you have found new columns during the pricing you
have to add those to the generated cuts. For this it is necessary to
set the flag 'modifiable' to TRUE. Do you modify the Gomory cuts
after pricing new variables? Otherwise your cuts are not valid for
your master problem.<br>
<br>
Probably you already know this but in the SCIP Optimization Suite
there is a Generic-Cut-and-Price framework (GCG) which performs a
Dantzig-Wolfe decomposition and solves the LP relaxation via column
generation. On the web page of GCG:<br>
<br>
<a class="moz-txt-link-freetext" href="http://www.or.rwth-aachen.de/gcg/">http://www.or.rwth-aachen.de/gcg/</a><br>
<br>
you might find some interesting papers like this one:<br>
<br>
<a class="moz-txt-link-freetext" href="http://www.or.rwth-aachen.de/research/publications/sea2015-basiscuts_01.pdf">http://www.or.rwth-aachen.de/research/publications/sea2015-basiscuts_01.pdf</a><br>
<br>
which explains how to obtain cuts for the original variables by
using basis information of the Simplex algorithm.<br>
<br>
Unfortunately, I am not an expert for branch-cut and price. Maybe
someone else can add some useful information or things I missed.<br>
<br>
<br>
Best regards,<br>
<br>
Benny<br>
<br>
<br>
<div class="moz-cite-prefix">On 07/09/2015 02:34 PM, <a class="moz-txt-link-abbreviated" href="mailto:dponce@us.es">dponce@us.es</a>
wrote:<br>
</div>
<blockquote cite="mid:8f44a45ebe768465ce500e17167cd251@us.es"
type="cite">
<p>Hello scip,</p>
<p>I'm implementing a column generation algorithm for a Binary
Linear Problem and I have a few questions about how could work a
separator on a B&P framework. In the FAQ (Specific questions
about Column Generation and Branch-And-Price with SCIP,9) it is
said that in most cases one should deactivate separators. But
for a Branch-and-Cut-and-Price I would like to implement my own
separator plugin. Which will be the main staff to take care of?</p>
<p>By the moment I've try to use Gomory cuts and what happens is
that it is called in every node but no cuts are added.</p>
<p>If I know how these valid inequalities affect my pricing
problem, could I implement the separator?</p>
<p>Regards and thanks in advance.</p>
<p>Diego Ponce.</p>
<p> </p>
<div> </div>
<br>
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<br>
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<pre class="moz-signature" cols="72">--
______________________________
Benjamin Müller
Zuse Institute Berlin
Takustr. 7, 14195 Berlin
<a class="moz-txt-link-abbreviated" href="mailto:benjamin.mueller@zib.de">benjamin.mueller@zib.de</a>
+49 30 841 85-195</pre>
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