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<div class="moz-cite-prefix">Marco,<br>
<br>
Should be fixed.<br>
<br>
The dual code correctly thought it should push a variable all the
way to its upper bound. Unhappily the upper bound was 1.3. Then
a later part of presolve worked out that that was infeasible for
an integer variable.<br>
<br>
The error occurred in CoinPresolveDoubleton which changed bounds
from 0,infinity to 0,1.3 without checking whether it was integer.
I have corrected code so bounds would be 0,1.<br>
<br>
John Forrest<br>
<br>
On 28/09/15 23:46, Haroldo Gambini Santos wrote:<br>
</div>
<blockquote cite="mid:5609C341.3030209@gmail.com" type="cite">
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Hi Marco,<br>
<br>
I found out that the problem is related to a presolving procedure
which tries to fix bounds using dual information.<br>
<br>
A <i>quick and dirty</i> fix is to change in<br>
<br>
Osi/src/OsiPresolve.cpp line 988<br>
<br>
if (dual) {<br>
to <br>
if ((dual)&&0) {<br>
<br>
to temporarily disable this processing...<br>
<br>
Hoping that a better fix comes soon,<br>
<br>
Cheers,<br>
<br>
Haroldo<br>
<br>
<div class="moz-cite-prefix">On 28-09-2015 06:22, mg wrote:<br>
</div>
<blockquote
cite="mid:CAOayR=a8v3OLZCBjNB2S=L_aVkOhviQ0RWohe_hM22T1LyJ7Hg@mail.gmail.com"
type="cite">
<div dir="ltr"><font face="monospace, monospace">Hi all,</font>
<div><font face="monospace, monospace">I've found a case where
preprocess says the problem is infeasible, but if I turn
preprocess off, the problem is correctly solved.</font></div>
<div><font face="monospace, monospace"><br>
</font></div>
<div><span style="font-size:12.8px"><font face="monospace,
monospace">Attached you can find the LP file (m3.lp). To
reproduce the problem you can use the following code (I
use callCbc):</font></span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px"><font face="monospace,
monospace"><span class="" style="white-space:pre"> </span>OsiClpSolverInterface
solver;</font></span></div>
<div><span style="font-size:12.8px"><font face="monospace,
monospace"><span class="" style="white-space:pre"> </span>CbcModel
model(solver);</font></span></div>
<div><span style="font-size:12.8px"><font face="monospace,
monospace"><span class="" style="white-space:pre"> </span>model.solver()->readLp("m3.lp");</font></span></div>
<div><span style="font-size:12.8px"><font face="monospace,
monospace"><span class="" style="white-space:pre"> </span>std::string
args("-heur off -cuts off -solve");</font></span></div>
<div><span style="font-size:12.8px"><font face="monospace,
monospace"><span class="" style="white-space:pre"> </span>//
using these arguments instead it works</font></span></div>
<div><span style="font-size:12.8px"><font face="monospace,
monospace"><span class="" style="white-space:pre"> </span>//
std::string args("-heur off -cuts off -preprocess off
-solve"); </font></span></div>
<div><span style="font-size:12.8px"><font face="monospace,
monospace"><span class="" style="white-space:pre"> </span>callCbc(args,
model); </font></span><br>
</div>
<div><span style="font-size:12.8px"><font face="monospace,
monospace"><br>
</font></span></div>
<div><font face="monospace, monospace"><span
style="font-size:12.8px">The problem happens in both
2.9.5 </span></font><span
style="font-family:monospace,monospace;font-size:12.8px">release</span><span
style="font-family:monospace,monospace;font-size:12.8px"> </span><span
style="font-size:12.8px;font-family:monospace,monospace">and
2.9.6 release versions.</span></div>
<div><span
style="font-size:12.8px;font-family:monospace,monospace"><br>
</span></div>
<div><span
style="font-size:12.8px;font-family:monospace,monospace">Thanks
in advance,</span></div>
<div><span
style="font-size:12.8px;font-family:monospace,monospace">Marco</span></div>
</div>
<br>
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<br>
<pre class="moz-signature" cols="72">--
==================================================
Haroldo Gambini Santos
D.Sc, Computer Science
Universidade Federal de Ouro Preto
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://www.decom.ufop.br/haroldo/">http://www.decom.ufop.br/haroldo/</a></pre>
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