<!DOCTYPE html>
<html data-lt-installed="true">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body style="padding-bottom: 1px;">
<p>Hi Marc,</p>
<p>i did terminate probing like this and I don't think that I
directly do anything to the LP, I just create a new probing node,
change bounds, solve the probing LP, backtrack, rinse and repeat.
The watchpoint on the stats did not directly reveal anything to me
other than that the lp->validsollp was not update in some
cases. I don't know why, but it seems this was the problem: if the
timing was SCIP_PROPTIMING_AFTERLPLOOP, i do two different probing
tests: so the LP is put into probing mode, probing is done,
probing mode is ended, then probing mode is immediately entered
again, probing is done, probing is ended. It seems that during the
second round of probing, the lp->validsollp was not properly
updated for whatever reason. I have now moved the SCIPstartProbing
and SCIPendProbing so that they are only called once per
propagation call and now i do not have the error anymore. <br>
</p>
<p>Thank you for the input!<br>
All the best<br>
Alex<br>
</p>
<div class="moz-cite-prefix">On 19.10.23 14:18, Marc Pfetsch wrote:<br>
</div>
<blockquote type="cite"
cite="mid:bc069290-dadc-4c99-9c81-3dbb38c5a766@mathematik.tu-darmstadt.de">
<br>
<br>
Hi Alex,
<br>
<br>
can you please check whether your propagation method terminates
the probing mode correctly (SCIPendProbing)? It also might be that
you call functions that disturb the LP status somehow.
<br>
<br>
If the problem is not immediate from your code, you could run your
code in a debugger and add a watchpoint on lp->validsollp and
stat->lpcount and see which function changes it. This might
help to track the problem down.
<br>
<br>
Best
<br>
<br>
Marc
<br>
<br>
<br>
<br>
<br>
On 19/10/2023 13:37, Alexander Helber wrote:
<br>
<blockquote type="cite">Dear SCIP community,
<br>
<br>
I am working on a Benders Decomposition where I also implement a
propagator that tries to fix some variables by solving probing
LPs. For many instances this works without problem but
sometimes, the assertion `assert(lp->validsollp ==
stat->lpcount);` of the function SCIPlpRemoveRedundantRows in
line 15956 of `lp.c` is triggered. This happens after my
propagator was called, when SCIP resumes solving the current
node LP, but not every time. It does not seem to indicate any
big problems, as I seem to get correct solutions when I ignore
the assertion. If I do not use my propagator, the error does not
seem to occur.
<br>
<br>
In any case, I wonder if someone has an idea what is going wrong
and if it may have negative consequences.
<br>
<br>
All the best,
<br>
Alex
<br>
<br>
-- <br>
Alexander Helber
<br>
Research and Teaching Assistant
<br>
<br>
Chair of Operations Research
<br>
RWTH Aachen University
<br>
Kackertstrasse 7
<br>
52072 Aachen
<br>
Germany
<br>
Web: or.rwth-aachen.de
<br>
<a class="moz-txt-link-abbreviated" href="mailto:Mail:helber@or.rwth-aachen.de">Mail:helber@or.rwth-aachen.de</a>
<br>
<br>
<br>
_______________________________________________
<br>
Scip mailing list
<br>
<a class="moz-txt-link-abbreviated" href="mailto:Scip@zib.de">Scip@zib.de</a>
<br>
<a class="moz-txt-link-freetext" href="https://listserv.zib.de/mailman/listinfo/scip">https://listserv.zib.de/mailman/listinfo/scip</a>
<br>
</blockquote>
_______________________________________________
<br>
Scip mailing list
<br>
<a class="moz-txt-link-abbreviated" href="mailto:Scip@zib.de">Scip@zib.de</a>
<br>
<a class="moz-txt-link-freetext" href="https://listserv.zib.de/mailman/listinfo/scip">https://listserv.zib.de/mailman/listinfo/scip</a>
<br>
</blockquote>
<pre class="moz-signature" cols="72">--
Alexander Helber
Research and Teaching Assistant
Chair of Operations Research
RWTH Aachen University
Kackertstrasse 7
52072 Aachen
Germany
Web: or.rwth-aachen.de
Mail: <a class="moz-txt-link-abbreviated" href="mailto:helber@or.rwth-aachen.de">helber@or.rwth-aachen.de</a></pre>
</body>
<lt-container></lt-container>
</html>