[Scip] Branch-Price to Branch-cut-Price

[Cristina Núñez del Toro]

Hello again,

I finally implemented a constraint handler (instead of a separator) in
order to add cutting planes during the pricing loop.

As you (Ambros) suggested me, I implemented the CONSINITLP callback.
However, when I do the execution, this callback never starts. I was
thinking that maybe I'm leaving out some starting parameter or putting some
variable in a incorrect way.
Is there a specific activation parameter that I must consider?

I'm pretty sure the Constraint Handler is running during the execution
because I am able to add cutting planes after finishing the pricing by
using the CONSSEPALP callback, however my intention is to use CONSINITLP
instead of CONNSEPALP.



Thank you for your help,




2014-06-12 10:24 GMT+02:00 Cristina Núñez del Toro <cristina.nunez at upc.edu>:

> Hello Ambros,
>
> My idea is to cutt off already the suboptimal LP solutions just before the
> pricing loop starts. What I want is to strengthen the LP solution before
> looking for new columns. However, doing it during the pricing loop may help
> as well.  I will try the CONSINITLP callback.
>
> Thank you.
>
>
>
> 2014-06-11 19:40 GMT+02:00 Ambros Gleixner <gleixner at zib.de>:
>
> Dear Cristina,
>>
>> as far as I know, you cannot call separators before pricing.  However,
>> you can implement the CONSINITLP callback of a constraint handler, which
>> can add cutting planes during the pricing loop.
>>
>> Maybe you can describe a bit better what you want to do exactly.  Would
>> you want to cut off already the suboptimal LP solutions during the pricing
>> loops (is that possible?) or add cutting planes that are independent of the
>> solution?
>>
>> Cheers,
>> Ambros
>>
>>
>>
>> Am 06.06.2014 19:30, schrieb Cristina Núñez del Toro:
>>
>>> Dear Mailing List,
>>>
>>> I am currently working on a Branch-and-Price algorithm. My next step is
>>> to strength the LP relaxation at nodes, so I implemented a plug-in
>>> separator in order to add cutting planes. My idea is to add cutting
>>> planes before start looking for new columns.
>>>
>>> However, I have noticed that at each node, the variable pricer plug-in
>>> is executed in the first place and then, when no more columns are added,
>>> the separator plug-in starts. Is there a way to change the order of the
>>> plug-in's execution? i.e., start first with the separator and then, when
>>> no more cuts can be added, execute the variable pricer? Maybe I am
>>> leaving outa callback ?
>>>
>>> Thanks in advance.
>>>
>>> --
>>> ---
>>> Cristina Nuñez
>>>
>>>
>>> _______________________________________________
>>> Scip mailing list
>>> Scip at zib.de
>>> http://listserv.zib.de/mailman/listinfo/scip
>>>
>>>
>> --
>> ____________________________________________________________
>> Ambros M. Gleixner
>> Zuse Institute Berlin - Matheon - Berlin Mathematical School
>> http://www.zib.de/gleixner
>> _______________________________________________
>> Scip mailing list
>> Scip at zib.de
>> http://listserv.zib.de/mailman/listinfo/scip
>>
>
>
>
> --
> ---
> Cristina Nuñez
>



-- 
---
Cristina Nuñez
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listserv.zib.de/pipermail/scip/attachments/20140619/4701852d/attachment.html>