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


From: Andrew Makhorin
Subject: Re: [Bug-glpk] FPUMP heuristic pass bug GLPK4.60
Date: Wed, 06 Apr 2016 14:19:58 +0300

> > 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.
> 

Also you can run glpsol with the option "--save filename" to save the
best integer feasible solutions found to a file and cancel the solver at
any time you want. Then you may use that saved solution as an initial
one with the option "--use filename",





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