[SCIP] Questions on detecting unbounded

[Gregor Hendel]

Hi  Yankai,

please read the documentation of SCIP, especially search the limits in 
the user parameters

http://scip.zib.de/doc/html/PARAMETERS.php

to find something that matches your purpose. IMHO, there is nothing to 
speed up the detection of unboundedness. What you should rather do, is 
set up a proper lower bound for your model, and set a solution limit of 
1 to stop if feasibility of this modified model was proven.

Happy scipping,
Gregor



Am 17.02.2017 um 17:02 schrieb Yankai Cao:
> Dear Benjamin,
>
>
> Thanks so much for your reply.  Is there any parameter I can set to help SCIP detect if the problem is unbound. For example, for my model, if SCIP find an upper bound <= ub (e.g. -1e10), I want SCIP to stop and declare the problem is unbound. Otherwise, it will takes SCIP much much more time to continue. Thanks.
>
>
> Regards,
> Yankai
>
>
>> On Feb 17, 2017, at 7:19 AM, Benjamin Müller <benjamin.mueller at zib.de> wrote:
>>
>> Dear Yankai,
>>
>> you can use
>>
>> 	set/limits/objective
>>
>> in order to set an objective limit. SCIP will then only look for solutions that have a better value than the given objective limit. You can think of it as an artificial upper bound for your (minimization) problem.
>>
>> As far as I can see it, there is no parameter to set an initial dual bound in SCIP. There is SCIPupdateLocalDualbound in the API that could be called during the SCIP_STAGE_PROBLEM stage.
>>
>> Regards,
>> Benjamin
>>
>>
>> On 02/17/2017 07:24 AM, Yankai Cao wrote:
>>> Hi, All,
>>>
>>> I am new to SCIP.  I want to know how to set a parameter  ub (e.g. -1e10) so that if SCIP find the upper bound is smaller than ub SCIP can stop and declare that the problem is unbounded?
>>>
>>> Also,  how to provide known upper/lower bounds before b&b, which might help speed the solution time of SCIP?
>>>
>>> Thanks very much!
>>>
>>>
>>> Regards,
>>> Yankai
>>>
>>>
>>> _______________________________________________
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>>> Scip at zib.de
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>>>
>> -- 
>> ______________________________
>> Benjamin Müller
>> Zuse Institute Berlin
>> Takustr. 7, 14195 Berlin
>> benjamin.mueller at zib.de
>> +49 30 841 85-195
>
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