[Cgl] Limit for GomoryCuts

[John Forrest]

Thomas,

As I am unable to justify it and as removing made a slight improvement 
on some very limited tests,  I have removed the 500 in Cgl/0.57 which is 
what cbc uses.

John

On 20/12/12 19:55, Thomas Schoenemann wrote:
> Hi all,
>
> my application of Cbc (where I added a GomoryCut generator) was 
> producing abnormally large cuts at the root node, although I had set a 
> limit. So I looked into the code and found this passage (line 679 of 
> GomoryCut.cpp):
>
>
>     limit = limitAtRoot_;
>     if (!info.pass) {
>       tolerance1=1.0;
>       tolerance2=1.0e-2;
>       tolerance3=1.0e-6;
>       tolerance6=1.0e-7;
>       tolerance9=1.0e-5;
>       if (!limit||limit>=500)        <----!!!!!!!!!!!!!
>     limit=numberColumns;
>     } else {
>
>
> It appears that Cbc does not set info.pass (whatever that signifies) 
> and in this case a limit of 500 or larger is simply ignored.
>
> I was wondering if there is a plausible reason for this. At the very 
> least I think this behavior should be documented in the text on 
> setLimitAtRoot(). Personally, I'd prefer if the part "||limit >= 500" 
> was removed, it does not make sense to me.
>
> I have a recent version of Cbc, checked out via svn (maybe there is 
> already a repository for 2.8?):
>
> URL: https://projects.coin-or.org/svn/Cbc/stable/2.7
> Basis des Projektarchivs: https://projects.coin-or.org/svn/Cbc
> UUID des Projektarchivs: 6f23a84d-0c12-0410-9f0c-b73a89ba9ce0
> Revision: 1833
> Knotentyp: Verzeichnis
> Plan: normal
> Letzter Autor: stefan
> Letzte geänderte Rev: 1833
> Letztes Änderungsdatum: 2012-12-04 11:21:49 +0100 (Di, 04. Dez 2012)
>
>
> If you need my help, let me know.
>
> Best regards,
>   Thomas Schoenemann
>
>
>
> _______________________________________________
> Cgl mailing list
> Cgl at list.coin-or.org
> http://list.coin-or.org/mailman/listinfo/cgl

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.coin-or.org/pipermail/cgl/attachments/20121221/1a4e998b/attachment.html>