[Scip] epsilon for functions isPositive, isZero, etc

[Alessia Violin]

Perfect, thanks to all you for the answers!

Alessia


On 01/27/2014 12:22 PM, Timo Berthold wrote:
> Hi Alessia,
>
> You can use SCIPchgRealParam() to change the parameter numerics/epsilon.
> Note that at many places in the code, SCIP uses SCIPisFeas...() checks
> which compare against the numerics/feastol parameter (and not the
> epsilon).
>
> Ciao
> Timo
>
>> Hello Matthias,
>>
>> thanks! Is there a function to change the epsilon once for all those
>> functions? it would be quicker to test different values!
>>
>> Alessia
>>
>>
>> On 01/27/2014 11:59 AM, Matthias Miltenberger wrote:
>>> Hi Alessia,
>>>
>>> SCIP uses 1e-9 as default epsilon for these functions. It can be changed
>>> to a value in the range of 1e-20 to 1e-3.
>>>
>>> best
>>> Matthias
>>>
>>> On 27.01.2014 11:17, Alessia Violin wrote:
>>>> Hello!
>>>>
>>>> I was wondering which is the "epsilon" used in the functions
>>>> SCIPisPosite, isZero, isEQ, etc? I tried to find this information in
>>>> the
>>>> developer's manual but I didn't succeed.
>>>>
>>>> I have a branch-and-cut-and-price code with quite a lot of other things
>>>> (stabilisation, heuristics, ...), and if the epsilon is too small the
>>>> convergence of column generation is very slow, and if it's too big
>>>> there
>>>> are some particular configurations of parameters for which optimal
>>>> columns are not generated. Moreover this also depends on the magnitude
>>>> of the data for different set of instances and I am trying to figure
>>>> out
>>>> the best epsilon to use.
>>>>
>>>> Thanks in advance!
>>>>
>>>> Alessia
>>>>
>>>>
>> --
>> Alessia Violin
>> Service Graphes et Optimisation Mathématique (G.O.M.)
>> Université Libre de Bruxelles
>> C.P. 210/01
>> Boulevard du Triomphe
>> B-1050 BRUXELLES
>> Tel: 02 650 58 80 - Fax: 02 650 59 70
>> Email: aviolin at ulb.ac.be
>> Webpage: http://homepages.ulb.ac.be/~aviolin/
>>
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>

-- 
Alessia Violin
Service Graphes et Optimisation Mathématique (G.O.M.)
Université Libre de Bruxelles
C.P. 210/01
Boulevard du Triomphe
B-1050 BRUXELLES
Tel: 02 650 58 80 - Fax: 02 650 59 70
Email: aviolin at ulb.ac.be
Webpage: http://homepages.ulb.ac.be/~aviolin/