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Re: [Bug-glpk] FPUMP heuristic pass bug GLPK4.60


From: Noli Sicad
Subject: Re: [Bug-glpk] FPUMP heuristic pass bug GLPK4.60
Date: Wed, 6 Apr 2016 21:29:22 +1000

I think this instance of the model is quite hard to solve.

I run glpsol for more than 1 hour and it did not find an initial
solution. Only fpump found a solution at pass 9 but I aborted it. I am
running it again.

I also run cbc-solver for 1 hour and 2 hours with same model. No
solution as well.

Noli

On 4/6/16, Andrew Makhorin <address@hidden> wrote:
>> OK. It is feature but it seems not a good feature.
>
>> I tried to modify the npass (default 5) to npass <=10 and fpump finds
>> a solution in npass 9 and it starts again from pass 1 to  pass 10. It
>> takes a long time to finish the job.
>>
>
> Well, all primal heuristic work in this way--usually it is reasonable to
> spent some time to find a good initial solution rather than to spent a
> lot of time to close a large integrality gap during the b&b search. The
> only question is when to stop. May be to add a time limit like for PROXY
> heuristic. On the other hand, if your instance is not hard, i.e. if the
> b&b solver finds an initial solution quickly, using primal heuristic(s)
> is not needed.
>
>
>



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