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

[Ambros Gleixner]

Dear Cristina,

I am guessing your constraint handler does not have any constraints and 
hence also no constraints marked as initial.  In this case, in 
cons.c:2690 (SCIP 3.1), SCIP returns before calling the consinitlp callback:

    if( conshdlr->ninitconss == 0 || (!initkeptconss &&
       conshdlr->ninitconss == conshdlr->ninitconsskept) )
          return SCIP_OKAY;

Could you analyze whether this is the case by adding some debug 
messages; if yes, then as a first workaround you could try to remove 
these lines.

(A cleaner solution could be to generally allow calling the callback in 
case CONSHDLR_NEEDSCONS is set to FALSE, but this needs some more 
discussion.)

Cheers,
ambros


Am 19.06.2014 11:20, schrieb 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 <mailto: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
>     <mailto: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
>
>
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>
>         --
>         ______________________________________________________________
>         Ambros M. Gleixner
>         Zuse Institute Berlin - Matheon - Berlin Mathematical School
>         http://www.zib.de/gleixner
>         _________________________________________________
>         Scip mailing list
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>
>
>
>
>     --
>     ---
>     Cristina Nuñez
>
>
>
>
> --
> ---
> Cristina Nuñez

-- 
____________________________________________________________
Ambros M. Gleixner
Zuse Institute Berlin - Matheon - Berlin Mathematical School
http://www.zib.de/gleixner