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<p>Hi John and others,</p>
<p> I'm trying to export the preprocessed model with '-preprocess
save' (getting a 'presolved.mps') file. Redoing the preprocess on
the model of the presolved.mps file is not making it smaller. It's
possible that I'm missing something. Is there any other way to
export the preprocessed model to reproduce what you are seeing?</p>
<p>Best regards,</p>
<p>Rui<br>
</p>
<br>
<div class="moz-cite-prefix">On 11/23/2019 10:00 AM, John Forrest
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:d3b1a346-3d19-4eb0-8753-6e1bb36cac7f@gmail.com">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>
John Forrest
<br>
<br>
On 22/11/2019 15:44, Rui Patrocínio wrote:
<br>
<blockquote type="cite">Hi,
<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 class="moz-txt-link-freetext" href="https://drive.google.com/open?id=1bd4jWONmoyAKIi0oLa-AU-ZTu7_8qhb6">https://drive.google.com/open?id=1bd4jWONmoyAKIi0oLa-AU-ZTu7_8qhb6</a>
<br>
<br>
-- <br>
SISCOG - Sistemas Cognitivos, SA
<br>
<br>
*Rui Patrocínio*
<br>
<br>
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</blockquote>
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<br>
</blockquote>
<br>
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<span style="font-size:10pt;color:#F37D00"><b><!-- COLOCAR AQUI O NOME -->
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