Torsten,<br><br>Did you get the integer optimal solution with all versions ?<br>I'm just thinking that perhaps the better bounds of previous versions could include inequalities which could cut integer optimal solutions - these issues perhaps are fixed in newest releases....<br>
<br><div class="gmail_quote">On Wed, Aug 26, 2009 at 12:26 PM, Torsten Fahle <span dir="ltr"><<a href="mailto:Torsten.Fahle@inform-ac.com">Torsten.Fahle@inform-ac.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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>
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e-mail: <a href="mailto:Torsten.Fahle@inform-ac.com">Torsten.Fahle@inform-ac.com</a> <a href="http://www.groundstar.de" target="_blank">http://www.groundstar.de</a><br>
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</blockquote></div><br><br clear="all"><br>-- <br>=============================================================<br>Haroldo Gambini Santos<br>Computing Department - Universidade Federal de Ouro Preto - UFOP<br>email: <a href="mailto:haroldo.santos@gmail.com">haroldo.santos@gmail.com</a><br>
home/research page: <a href="http://www.ic.uff.br/~hsantos/">http://www.ic.uff.br/~hsantos/</a><br><br>“BE the change you want to see in the world” -Mahatma Gandhi<br><br>