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

[michael.winkler at zib.de]

"read yourfilename.sol" in the interactive shell

Best, Micha

> 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
>