[Cbc] Improving performance for binary model

[Rui Patrocínio]

Hi John and others,

  I'm trying to export the preprocessed model with '-preprocess save' 
(getting a 'presolved.mps') file. Redoing the preprocess on the model of 
the presolved.mps file is not making it smaller. It's possible that I'm 
missing something. Is there any other way to export the preprocessed 
model to reproduce what you are seeing?

Best regards,

Rui


On 11/23/2019 10:00 AM, John Forrest wrote:
> My guess is that Cbc is very bad at handling symmetry.  There is a lot 
> of symmetry and trying some of the ways that Cbc can deal with 
> symmetry I can get a solution of 296773 fairly quickly, but after an 
> hour it does not seem to be closing the gap.  The other area where Cbc 
> is failing somewhat is preprocessing - if I export the model several 
> times (each time doing presolve) then I can make it smaller - this 
> obviously wrong.
>
> John Forrest
>
> On 22/11/2019 15:44, Rui Patrocínio wrote:
>> Hi,
>>
>>   I'm trying to solve one instance of a problem that is taking a long 
>> time to obtain a good solution. Since all variables are binary, 
>> probing and implication cuts are doing some work and RINS and Vnd are 
>> apparently also improving solutions. For other instances of the 
>> problem we are solving, CBC has an acceptable performance but for 
>> this instance apparently there's something going wrong (~20 seconds 
>> to get the optimum solution with a commercial solver versus never 
>> getting the optimum solution with CBC).
>>
>>   If someone can take a look at the model and give me a hint of what 
>> is going on, I would appreciate it.
>>
>>   The model is at 
>> https://drive.google.com/open?id=1bd4jWONmoyAKIi0oLa-AU-ZTu7_8qhb6
>>
>> -- 
>> SISCOG - Sistemas Cognitivos, SA
>>
>> *Rui Patrocínio*
>>
>> _______________________________________________
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>>
>
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-- 
SISCOG - Sistemas Cognitivos, SA

*Rui Patrocínio*
Scheduling Team Leader

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