[SCIP] Setting relative gap in FiberSCIP and ParaSCIP

[Yuji Shinano]

Dear Vladimir,

|Stefan Vigerske and I tried to implement it so that it works more precisely.
Probably, the code is already released in the version.
Please try to use the command line option with "-sl gap.set", and the file gap.set inclueds
"limits/gap" or "limits/absgap". Then, it would work better than the previous versions.
Please let me know the results.
||@Stefan: If you can say something else, please add your comments.

Best regards,
Yuji
|
On 24.04.23 1:06, Vladimir V. Voloshinov wrote:
> Dear Yuji,
> excuse for bothering you, but I see that SCIP Opt. Suite 8.0.3 includes UG 1.0 already.
> I see that the parameter CheckGapInLC, which we tried to use, has been excluded from the list of UG options, so it seems that some changes with "gap management" happened...
> But I see that the gap set in the scip.set file does not affect FiberSCIP which still solves problem till zero gap.
> Moreover, I see in ug/src/ug_scip/scipParaSolver.cpp, lines #1259,#1260, that "limits/gap" and "limits/absgap" are "hardcoded" to be 0...
> Maybe we missed something, but is it possible to set a non zero gap for FiberSCIP (and ParaSCIP) now, since version 8.0.3? It is very important in some circumstances...
>
> Best regards,
> Vladimir
>
> On Mon, Sep 12, 2022 at 5:36 PM Yuji Shinano <shinano at zib.de> wrote:
>
>     Hi Sergey,
>
>     On 12.09.22 16:17, Sergey Smirnov wrote:
>     > Thank you for checking my instance.
>     >
>     > We also tried setting CheckGapInLC=TRUE but it did not help either.
>
>     Thanks for testing it, too. Probably, I tried to implement it once,
>     but I had some issues realizing it. Before UG version 1.0,
>     UG was a bit hard to specialize for a specific "base solver" parallelization.
>     In current UG version 1.0, it is easy to implement some features
>     specialized to a specific "base solver".
>     I will let you know when I add the feature to FiberSCIP and ParaSCIP.
>
>     Best,
>     Yuji
>
>     >
>     >> On 11 Sep 2022, at 17:42, Yuji Shinano <shinano at zib.de> wrote:
>     >>
>     >> Hi Sergey,
>     >>
>     >> Thanks for the instance and configuration. I checked it.
>     >> Sorry, in the current implementation of FiberSCIP and ParaSCIP, controlling it only with the SCIP parameter looks difficult when it takes time to solve
>     >> (if it can be solved in the racing stage, the "NoPreprocessingInLC = TRUE" might work).
>     >> And it looks like the setting SCIP parameters for that is not good for FiberSCIP and ParaSCIP in a sense how it work is not clear.
>     >> I will add the feature rather UG side in the future. I think it can not control vividly, but when LC recognized that gap is reached,
>     >> then LC interrupts all computations from the UG side.
>     >>
>     >> Best regards,
>     >> Yuji
>     >>
>     >> --------------
>     >> Hi Yuji,
>     >>
>     >> Here are the instance and configuration files attached.
>     >>
>     >> Thank you in advance,
>     >> Best regards,
>     >> Sergey
>     >>
>     >>
>     >> > On 10 Sep 2022, at 08:55, Yuji Shinano <shinano at zib.de> wrote:
>     >> >
>     >> > Hi Sergey,
>     >> >
>     >> > Can you send me the instance and parameters (UG and SCIP)? I will check it.
>     >> >
>     >> > Best regards,
>     >> > Yuji
>     >> >
>     >> > On 10.09.22 6:50, Sergey Smirnov wrote:
>     >> >> Hi Yuji,
>     >> >>
>     >> >> Thank you for the suggestion. I tried to set NoPreprocessingInLC = TRUE in ug.set but both fscip and parascip still solved till zero gap.
>     >> >>
>     >> >> Best regards,
>     >> >> Sergey
>     >> >>
>     >> >>> On 9 Sep 2022, at 21:20, Yuji Shinano <shinano at zib.de> wrote:
>     >> >>>
>     >> >>> Hi,
>     >> >>>
>     >> >>> This is one of the frequently asked questions. FiberSCIP/ParaSCIP solves the presolved instance in the Solvers.
>     >> >>> Therefore, the value is applied to solve the presolved instance. If you would like to control the gap more precisely,
>     >> >>> one way would be to set
>     >> >>>  NoPreprocessingInLC = TRUE
>     >> >>> In the UG parameter file.
>     >> >>> However, this means that layered presolving does not work and may decrease its performance.
>     >> >>> Please try to run with the above parameter.
>     >> >>>
>     >> >>> Best,
>     >> >>> Yuji
>     >> >>>
>     >>
>     >>
>     >> On 09.09.22 19:45, Sergey Smirnov wrote:
>     >>> Hello, SCIP community,
>     >>>
>     >>> I have problems setting relative gap in parallel version of SCIP 8.0.1.
>     >>>
>     >>> When I set limits/gap = .5e-01 in scip.set and run scip like scip -f problem.cip -s scip.set  scip stops after reaching the gap specified. However, fscip and parascip seem to ignore this parameter. For example, I run fscip the following way and it solves until optimality:
>     >>> fscip ug.set problem.cip -s scip.set
>     >>>
>     >>> What is the correct way to set relative gap in fscip/parascip?
>     >>>
>     >>> Thank you in advance,
>     >>> Best regards,
>     >>> Sergey
>     >>>
>     >>>
>     >>> _______________________________________________
>     >>> Scip mailing list
>     >>> Scip at zib.de
>     >>> https://listserv.zib.de/mailman/listinfo/scip
>     >>
>     >>
>     >> --
>     >> --------------------------------------------------
>     >> Yuji Shinano
>     >> Zuse Institute Berlin
>     >> Takustrasse 7, 14195 Berlin-Dahlem, Germany
>     >> Phone:+49 30 84185-477, Fax:+49 30 84185-269
>     >>
>     >> _______________________________________________
>     >> Scip mailing list
>     >> Scip at zib.de
>     >> https://listserv.zib.de/mailman/listinfo/scip
>     >
>
>
>     -- 
>     --------------------------------------------------
>     Yuji Shinano
>     Zuse Institute Berlin
>     Takustrasse 7, 14195 Berlin-Dahlem, Germany
>     Phone:+49 30 84185-477, Fax:+49 30 84185-269
>
>     _______________________________________________
>     Scip mailing list
>     Scip at zib.de
>     https://listserv.zib.de/mailman/listinfo/scip
>
>
>
> -- 
> Vladimir V. Voloshinov,
> Ph.D, head of lab. C-3 "Distributed computing algorithms", http://www.iitp.ru/ru/researchlabs/1040.htm,
> Center for Distributed Computing, Institute for Information Transmission Problems RAS, http://www.iitp.ru
> web: GoogleScholar profile <https://scholar.google.ru/citations?hl=en&user=-m4QhNEAAAAJ&view_op=list_works&sortby=pubdate>


-- 
--------------------------------------------------
Yuji Shinano
Zuse Institute Berlin
Takustrasse 7, 14195 Berlin-Dahlem, Germany
Phone:+49 30 84185-477, Fax:+49 30 84185-269
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