[SCIP] Setting relative gap in FiberSCIP and ParaSCIP

[Yuji Shinano]

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