[Cbc] Cut efficiency in cbcSolve for versions 2.0.0, 2.1.0, 2.2.2 and 2.3.0

[Haroldo Santos]

Torsten,

Did you get the integer optimal solution with all versions ?
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....

On Wed, Aug 26, 2009 at 12:26 PM, Torsten Fahle <Torsten.Fahle at inform-ac.com
> wrote:

> Hi,
>
> When testing with older cbcSolver versions we were surprised  to see that
> the lower bound in the root node after adding cuts
> differs significantly between different cbc releases:
>
> On a test case the root node after cuts had a lower bound of
> 195.305  (CBC 2.0.0)
> 221.561  (CBC 2.1.0)
> 160.296  (CBC 2.2.2 and 2.3.0)
>
> The initial LP bound is 160.236, the optimal solution 246.296.
> This means almost no improvement by root cuts in CBC 2.2.2 and 2.3.0. The
> initial gap is 53%
> In CBC 2.0.0 and 2.1.0 there is a significant improvement, the initial gap
> is 26%, and 11%, resp.
>
> 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
> other setting stops probing from being as effective as in older versions?
>
> All tests were performed using MS Visual Studio 2005 on an Intel QuadCore
> CPU using Debug mode.
> There are numerical differences between release and debug version in this
> setting. I hope the effect
> is nevertheless still reproducible.
>
> I've filed a ticket (#78) with more details on the case. Maybe someone can
> investigate this case and find
>
> Thanks !
>
>  Torsten
>
> --
>
> Dr. Torsten Fahle
> Airport Systems Division
> INFORM GmbH, Pascalstr.23, 52076 Aachen, Germany
> Tel. (+49) 24 08 - 94 56 24  FAX: -94 56 25
> e-mail: Torsten.Fahle at inform-ac.com   http://www.groundstar.de
> INFORM Institut fuer Operations Research und Management GmbH
> Registered AmtsG Aachen HRB1144 Gfhr.Adrian Weiler
>
>
>
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-- 
=============================================================
Haroldo Gambini Santos
Computing Department - Universidade Federal de Ouro Preto - UFOP
email: haroldo.santos at gmail.com
home/research page:  http://www.ic.uff.br/~hsantos/

“BE the change you want to see in the world” -Mahatma Gandhi
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