[SCIP] Setting relative gap in FiberSCIP and ParaSCIP

[Yuji Shinano]

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
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>> 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