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<p>Torsten,<br>
<br>
Techniques such as probing can be very expensive and default settings have been changed between versions. What happens if you try and force more probing e.g. -probing forceonstrong? Also it could be a bug of sorts.<br>
<br>
If you want, you can send me the problem for me to see if there is a bug (as long as it is not too large).<br>
<br>
John Forrest<br>
<br>
<img width="16" height="16" src="cid:1__=0ABBFC8CDFBBFF948f9e8a93df938@us.ibm.com" border="0" alt="Inactive hide details for "Torsten Fahle" ---08/26/2009 11:32:58 AM---Hi, When testing with older cbcSolver versions we were su"><font color="#424282">"Torsten Fahle" ---08/26/2009 11:32:58 AM---Hi, When testing with older cbcSolver versions we were surprised to see that the lower bound in the</font><br>
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<font size="2" color="#5F5F5F">From:</font></td><td width="100%"><img width="1" height="1" src="cid:2__=0ABBFC8CDFBBFF948f9e8a93df938@us.ibm.com" border="0" alt=""><br>
<font size="2">"Torsten Fahle" <Torsten.Fahle@inform-ac.com></font></td></tr>
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<font size="2"><cbc@list.coin-or.org></font></td></tr>
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<font size="2" color="#5F5F5F">Date:</font></td><td width="100%"><img width="1" height="1" src="cid:2__=0ABBFC8CDFBBFF948f9e8a93df938@us.ibm.com" border="0" alt=""><br>
<font size="2">08/26/2009 11:32 AM</font></td></tr>
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<font size="2" color="#5F5F5F">Subject:</font></td><td width="100%"><img width="1" height="1" src="cid:2__=0ABBFC8CDFBBFF948f9e8a93df938@us.ibm.com" border="0" alt=""><br>
<font size="2">[Cbc] Cut efficiency in cbcSolve for versions 2.0.0, 2.1.0, 2.2.2 and 2.3.0</font></td></tr>
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<font size="2">cbc-bounces@list.coin-or.org</font></td></tr>
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<tt>Hi,<br>
<br>
When testing with older cbcSolver versions we were surprised to see that the lower bound in the root node after adding cuts<br>
differs significantly between different cbc releases:<br>
<br>
On a test case the root node after cuts had a lower bound of <br>
195.305 (CBC 2.0.0)<br>
221.561 (CBC 2.1.0)<br>
160.296 (CBC 2.2.2 and 2.3.0)<br>
<br>
The initial LP bound is 160.236, the optimal solution 246.296.<br>
This means almost no improvement by root cuts in CBC 2.2.2 and 2.3.0. The initial gap is 53%<br>
In CBC 2.0.0 and 2.1.0 there is a significant improvement, the initial gap is 26%, and 11%, resp.<br>
<br>
It seems that probing is not as efficient in cbcSolve 2.2.2 and 2.3.0 as it was in cbcSolve 2.0.0 and 2.1.0( after some tuning). Maybe there is a small bug in probing or some <br>
other setting stops probing from being as effective as in older versions?<br>
<br>
All tests were performed using MS Visual Studio 2005 on an Intel QuadCore CPU using Debug mode. <br>
There are numerical differences between release and debug version in this setting. I hope the effect<br>
is nevertheless still reproducible.<br>
<br>
I've filed a ticket (#78) with more details on the case. Maybe someone can investigate this case and find <br>
<br>
Thanks !<br>
<br>
Torsten<br>
<br>
-- <br>
<br>
Dr. Torsten Fahle<br>
Airport Systems Division<br>
INFORM GmbH, Pascalstr.23, 52076 Aachen, Germany<br>
Tel. (+49) 24 08 - 94 56 24 FAX: -94 56 25<br>
e-mail: Torsten.Fahle@inform-ac.com </tt><tt><a href="http://www.groundstar.de">http://www.groundstar.de</a></tt><tt> <br>
INFORM Institut fuer Operations Research und Management GmbH<br>
Registered AmtsG Aachen HRB1144 Gfhr.Adrian Weiler<br>
<br>
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