<br><font size=2 face="sans-serif">This is a case of less is more - using
trunk</font>
<br>
<br><font size=2 face="sans-serif">cbc -solve
9.81</font>
<br><font size=2 face="sans-serif">cbc -cuts off -solve
1.08</font>
<br><font size=2 face="sans-serif">cbc -cuts off -preprocess off -solve
0.71</font>
<br><font size=2 face="sans-serif">cbc -cuts off -strong 0 -preprocess
off -solve 0.53</font>
<br><font size=2 face="sans-serif">cbc -cuts off -strong 0 -preprocess
off -heuristic off -solve 0.30</font>
<br>
<br><font size=2 face="sans-serif">As you can see the cuts are the main
culprit. The code thinks they are doing good but they do not seem
to do much. Interestingly neither flow cover or mixed integer rounding
give any cuts - while they do in cplex.</font>
<br>
<br><font size=2 face="sans-serif">For larger problems it may still be
worth doing preprocessing. Also switching back on feasibility pump
is marginally better.</font>
<br>
<br><font size=2 face="sans-serif">(Note - I have just updated trunk so
that strong=0 switches off strong branching altogether - with previous
version it would be -strong 0 -trust 0)</font>
<br>
<br><font size=2 face="sans-serif">John Forrest</font>
<br>
<br>
<br>
<br>
<br>
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<td width=40%><font size=1 face="sans-serif"><b>Michal Kaut <mail@michalkaut.net></b>
</font>
<br><font size=1 face="sans-serif">Sent by: coin-discuss-bounces@list.coin-or.org</font>
<p><font size=1 face="sans-serif">01/26/2007 08:06 AM</font>
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<div align=center><font size=1 face="sans-serif">Please respond to<br>
michal.kaut@hiMolde.no; Please respond to<br>
Discussions about open source software for Operations Research
<coin-discuss@list.coin-or.org></font></div></table>
<br>
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<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">To</font></div>
<td><font size=1 face="sans-serif">coin-discuss@list.coin-or.org</font>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
<td>
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<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">[Coin-discuss] How to speed-up Cbc?</font></table>
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<br>
<br>
<br><tt><font size=2>Hello,<br>
<br>
I am working with a MIP problem. I have tried a couple of solvers and <br>
Cbc is by far the slowest one. Can someone give me a hint which options
<br>
can I use to speed this particular problem up? I attach an MPS file.<br>
<br>
On my computer, CPLEX uses under 0.5 seconds, glpsol (from GLPK) 0.2 <br>
seconds(!) and lpsolve 3.5 seconds, while Cbc with default settings <br>
almost 16 seconds. I tried both my own compiled binary (Windows with <br>
MSYS and MinGW) and both binaries from the "Coin Binary" project.<br>
<br>
I tried several options and found that I can get the time down to 6.5 <br>
seconds using "-heur off", but it is still much slower than the
rest.<br>
Note that this just a test example. I have a bigger version that takes
<br>
under 40 seconds with both CPLEX and glpsol, while Cbc did not solve it
<br>
in more than 20 minutes (then I gave up and stopped it).<br>
<br>
<br>
Any help would be appreciated.<br>
<br>
Regards,<br>
Michal Kaut<br>
[attachment "small_test.zip" deleted by John J Forrest/Watson/IBM]
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