[Scip] Problem solving a large problems with many binary variables

[Alan Porto Bontempo]

Thanks All for reply,

How can I load a .sol file in scip command line?

I can read the problem but I did not found any command to evaluate the
problem with the given solution.

Thanks.




2014-07-15 12:55 GMT-03:00 <michael.winkler at zib.de>:

> Hi Alan,
>
> > Hi,
> >
> > I have a large problem to solve:
> >
> > original problem has 3646 variables (503 bin, 0 int, 0 impl, 3143 cont)
> > and
> > 7619 constraints
> >
> > I know this problem has a solution because gurobi solve it very fast and
> > scip says me it is infeasible.
> >
>
> This does not necessary mean that the problem is feasible (nor that it is
> infeasible). Probably your model is numerically not well-conditioned or
> there is a bug. Maybe you can send the model to me directly and I can have
> a look.
>
> Most of your changed parameters do not influence the result of SCIPs run.
>
> > For now i am using this sets of configurations:
> >
> > # maximal time in seconds to run
> > # [type: real, range: [0,1.79769313486232e+308], default: 1e+20]
> > limits/time = 1000
> >
> > # solving stops, if the absolute gap = |primalbound - dualbound| is below
> > the given value
> > # [type: real, range: [0,1.79769313486232e+308], default: 0]
> > limits/absgap = 1e-5
> >
> > # solving stops, if the relative gap = |primal -
> > dual|/MIN(|dual|,|primal|)
> > is below the given value
> > # [type: real, range: [0,1.79769313486232e+308], default: 0]
> > limits/gap = 0.0001
> >
> > # maximal number of nodes to process (-1: no limit)
> > # [type: longint, range: [-1,9223372036854775807], default: -1]
> > limits/nodes = 40000
> >
> > # maximal number of total nodes (incl. restarts) to process (-1: no
> limit)
> > # [type: longint, range: [-1,9223372036854775807], default: -1]
> > limits/totalnodes = 200000
> >
>
> All the above only lead to an early termination of the optimization
> process. (Also the totalnodes of 200000 are certainly not reached because
> the nodelimit of 40000 per run will be enough.)
>
> > # maximal memory usage in MB; reported memory usage is lower than real
> > memory usage!
> > # [type: real, range: [0,1.79769313486232e+308], default: 1e+20]
> > limits/memory = 250
> >
>
> This can change the solution path in the B&B tree, but will most likely
> also lead to a early termination.
>
> > # feasibility tolerance for constraints
> > # [type: real, range: [1e-17,0.001], default: 1e-06]
> > numerics/feastol = 1e-8
> >
>
> By decreasing the feasibility tolerance values above, you force SCIP to
> solve your model "more correctly". Maybe you want to relax the feasibility
> tolerance to allow slightly violated solutions?
>
> > What other configurations i can set to try to make my problem feasible?
> Or
> > what changes can I make to its set of configurations?
> >
>
> If you send us/me the model, maybe we/I can say more.
>
> > In the gurobi solution there are many small negative values, how do i
> > allow
> > this kind of things in scip?
> >
>
> Does this mean, that these values are slighty outside the bounds? Then
> maybe decreasing the feasibility tolerance can help, but actually there is
> no guarantee to find such a solution.
>
> You should also check if Gurobis solution is feasible by copying the
> solution into a .sol file and reading it into SCIP (after the problem was
> read). Then start optimizing, and the solution will then be checked.
>
> Best, Michael
>
> > Thanks.
> >
> > --
> > Até.
> >
> > Alan Porto Bontempo
> > _______________________________________________
> > Scip mailing list
> > Scip at zib.de
> > http://listserv.zib.de/mailman/listinfo/scip
> >
>
>
>


-- 
Até.

Alan Porto Bontempo
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