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<div class="moz-cite-prefix">Dear Vladimir<br>
<br>
In addition to what Marc wrote, I suggest that you check SCIP's <a
href="http://scip.zib.de/doc-3.1.0/html/CHANGELOG.php">changelog</a>
which contains a section about changed parameters between the
versions. <br>
<br>
I see that on your particular instance the number of solving nodes
has increased by about a factor of 15, which should focus your
attentions on changes w.r.t. branching. <br>
Between versions, we decreased the parameter
branching/relpscost/maxreliable from 8.0 to 5.0 which might be
disadvantageous for your problem. You may try to reset the
parameter to 8.0 or even a higher value and check if this improves
the performance. <br>
<br>
Hope this helps,<br>
Gregor<br>
<br>
Am 06.06.2014 19:09, schrieb Marc Pfetsch:<br>
</div>
<blockquote cite="mid:5391F5D0.6060502@mathematik.tu-darmstadt.de"
type="cite">
<br>
<br>
Hi Vladimir,
<br>
<br>
it is likely that you experienced what is called performance
variability: Small changes in the implementation of the
(LP-)solver (or input) can lead to a completely different solution
process. This cannot really be avoided.
<br>
<br>
More information can be found in answers to the following email to
this list:
<br>
<br>
<a class="moz-txt-link-freetext" href="http://listserv.zib.de/pipermail/scip/2013-November/001734.html">http://listserv.zib.de/pipermail/scip/2013-November/001734.html</a>
<br>
<br>
If the newer version is consistently slower on a very large
testset, however, the reason possibly is more structural.
<br>
<br>
Best
<br>
<br>
Marc
<br>
<br>
<br>
On 06.06.2014 16:34, Vladimir VV wrote:
<br>
<blockquote type="cite">Dear SCIP team,
<br>
I was surprised when found than last version of Scip works more
slowly
<br>
than previous 3.0.2 did.
<br>
For example, the same MILP problem of the following dimensions
(from
<br>
scipampl log):
<br>
"... 134 variables (114 bin, 0 int, 0 impl, 20 cont) and 1159
constraints"
<br>
has been solved by SCIP 3.0.2 in ~170 sec.
<br>
"Solving Time (sec) : 169.58
<br>
Solving Nodes : 210199
<br>
Primal Bound : +8.38888888888988e+00 (51 solutions)"
<br>
and by SCIP 3.1.0 in ~900 sec.
<br>
"Solving Time (sec) : 891.05
<br>
Solving Nodes : 3333047
<br>
Primal Bound : +8.38888888888929e+00 (41 solutions)
<br>
Dual Bound : +8.38888888888929e+00"
<br>
<br>
Both solvers had run with the default parameters settings at the
same host.
<br>
But looking at solvers' outputs I see that 3.1.0 processes the
search
<br>
tree completely differently than 3.0.2 does.
<br>
<br>
The same effect I see with many other problems... What is the
reason of that?
<br>
<br>
</blockquote>
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</blockquote>
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