[Scip] pool active columns size

[Gerald Gamrath]

Hi Mattia,

sorry for the late reply.
You cannot directly limit the number of columns in the LP, but you can
change some parameters so that SCIP deletes columns from the LP faster.
The parameter "lp/colagelimit" defines the age, i.e. the number of
consecutive LP solving calls for which the column had value 0.0, after
which the column is removed from the LP. You can decrease it (per
default it is set to 10) in order to remove variables from the LP faster.
Alternatively or in addition to that, you can set the parameters
"lp/cleanupcols" and "lp/cleanupcolsroot" to TRUE, so that all non-basic
columns created at this node which have value 0.0 are deleted from the LP.
For both variants, you need to set the "removable" parameter to TRUE for
the variables created in the pricing process.

I hope this helps for solving your problem.

Best regards,
Gerald


Am 01.06.2010 19:38, schrieb Mattia Barbieri:
> Hi all,
>  I am developing a branch&price application. I noticed that too many
> columns are added by my pricer (correctly, due to my model). I know
> (from a previous question), that SCIP keep a pool of active columns
> participating the LP (at each node). I suppose that if no negative
> reduced cost columns are found, before calling the pricer, SCIP looks
> out of the pool of active columns, to find a columns with a negative
> reduced cost (now). I think for my purposes will help to control the
> pool size (for example, to keep the number of current variables in LP
> under one-two thousands. Values greater than these significantly slow
> the computation, with my istances). So the question is: is there such
> a way to control the pool of active column size? (perhaps a parameter
> in scip.set?)
>
>    Thanks in advance.
>    Best regards,
>  
> Mattia Barbieri
> barbieri.mattia at gmail.com <mailto:barbieri.mattia at gmail.com>
>
>
> _______________________________________________
> Scip mailing list
> Scip at zib.de
> http://listserv.zib.de/mailman/listinfo/scip
>   

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://listserv.zib.de/mailman/private/scip/attachments/20100609/37a45e94/attachment.html