Or-tools: Passing solver parameters

[prezaei85]

Currently, SetSolverSpecificParametersAsString() does not work, at least in C# for SCIP. I have passed "limits/time = 60" to limit optimization time to 60 seconds or set "limits/totalnodes = 100" to limit the number of nodes, but none of them work successfully. There seems to be no other way to pass parameters also to other solvers, e.g., CPLEX, right now. Solving MIP problems usually requires to pass at least some solver tuning parameters to improve performance.

[lperron]

For time limits, you can use MpSolver.SetTimeLimit(int64 time_limit_in_ms).

Now I wonder why it does not work as the function is implemented. I will
have a look.
Laurent Perron | Operations Research | [email protected] | (33) 1 42 68 53
00

Le jeu. 5 avr. 2018 à 16:52, Pooya Rezaei [e-mail] a
écrit :

Currently, SetSolverSpecificParametersAsString() does not work, at least
in C# for SCIP. I have passed "limits/time = 60" to limit optimization time
to 60 seconds or set "limits/totalnodes = 100" to limit the number of
nodes, but none of them work successfully. There seems to be no other way
to pass parameters also to other solvers, e.g., CPLEX, right now. Solving
MIP problems usually requires to pass at least some solver tuning
parameters to improve performance.

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[amirmm11]

Any update? I also want to know how to pass solver parameters. I'd really appreciate if someone can help me.

[praveenxrao]

Hello, any update? I am trying to set GAP limit but unable to find a way to set it. Help is appreciated. Thank you

[prezaei85]

Relative MIP Gap is probably the only parameter that can be set directly using SetDoubleParam, and does not need to be passed as string. For other parameters, there is still no way.

namespace Google.OrTools.LinearSolver
{
    public class MPSolverParameters : IDisposable
    {
        public static readonly int RELATIVE_MIP_GAP;
        protected bool swigCMemOwn;

        public MPSolverParameters();

        ~MPSolverParameters();

        public static double kDefaultPrimalTolerance { get; }

        public virtual void Dispose();
        public double GetDoubleParam(int param);
        public void SetDoubleParam(int param, double value);
    }
}

[praveenxrao]

Thanks for the feedback Pooya.
I am trying to do this in Python and cannot find any attribute ‘SetDoubleParam’ in the solver object.

Any thoughts?

Thanks

Here is my code snippet:

 solver = pywraplp.Solver('ScheduleBuilder',
pywraplp.Solver.CBC_MIXED_INTEGER_PROGRAMMING)
#solver.SetTimeLimit(4000)
 solver.SetDoubleParam(solver.RELATIVE_MIP_GAP, 0.02)
gap = solver.GetDoubleParam(solver.RELATIVE_MIP_GAP)
print("GAP param: %f" % gap)

From: Pooya Rezaei [e-mail]
Reply-To: google/or-tools [e-mail]
Date: Thursday, May 17, 2018 at 10:34 AM
To: google/or-tools [e-mail]
Cc: "Rao, Praveen" [e-mail], Comment [e-mail]
Subject: Re: [google/or-tools] Passing solver parameters (#644)

Relative MIP Gap is probably the only parameter that can be set directly using SetDoubleParam, and does not need to passed as string. For other parameters, there is still no way.

namespace Google.OrTools.LinearSolver
{
public class MPSolverParameters : IDisposable
{
public static readonly int RELATIVE_MIP_GAP;
protected bool swigCMemOwn;

public MPSolverParameters();



~MPSolverParameters();



public static double kDefaultPrimalTolerance { get; }



public virtual void Dispose();

public double GetDoubleParam(int param);

public void SetDoubleParam(int param, double value);

}

}

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[prezaei85]

It is not under Solver. It is under MPSolverParameters. You need to instantiate that object, set MIP Gap and then pass MPSolverParameters to the Solve() method.

[lperron]

I assume this is fixed.

[danmarinescu]

See my answer here #603 for how to use SetSolverSpecificParametersAsString (with CPLEX, same concept might also apply to SCIP)

[rlloretb]

Any news on how to pass any solver parameters for SCIP solver? I mean not just time limit and relative MIP gap.

[lperron]

Relative mip gap can be set directly on the solver.

create a MPSolverParameters,
SetDoubleParam(MPSolverParameters.RELATIVE_MIP_GAP, value)

then pass to Solve(parameters)
Laurent Perron | Operations Research | [email protected] | (33) 1 42 68 53
00

Le ven. 10 mai 2019 à 05:36, rlloretb [e-mail] a écrit :

Any news on how to pass any solver parameters for SCIP solver? I mean not
just time limit and relative MIP gap.

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[rlloretb]

And what about any other command that it is not time_limit or relative_MIP_gap (via set SetSolverSpecificParametersAsString?)
I am particularly interested in CBC and SCIP.