[SCIP] Setting relative gap in FiberSCIP and ParaSCIP

[Vladimir V. Voloshinov]

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
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>


-- 
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>
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