Unable to set Solver Specific Parameter for XPRESS in JAVA

[SnehasishChar]

Version: 9.9.3963
Language: Java

Solver: XPRESS

OS: Windows

I am trying to update the value of the control parameters of XPRESS solver to improve the performance. But the values are not updating accordingly for some specific parameter..

I am trying to update in the following way:

String mipAbsStop = "MIPABSSTOP " + eps_optimal_absolute;
String optimalityTol = "OPTIMALITYTOL " + eps_optimal_absolute;
String mipRelStop = "MIPRELSTOP " + eps_optimal_relative;
String maxTime = "SOLTIMELIMIT " + solveTimeLimit;
String heurEmp = "HEUREMPHASIS " + 1;
String cutStrategy = "CUTSTRATEGY " + 1;
String feasTol = "FEASTOL " + eps_optimal_absolute;
String solverParams = optimalityTol + " " + mipRelStop + " " + maxTime + " " + heurEmp + " "
		+ cutStrategy + " " + mipAbsStop + " " + feasTol;

solver.setSolverSpecificParametersAsString(solverParams);

The values that are not getting set is as follows:

• OPTIMALITYTOL
• FEASTOL

[lperron]

try with \n after each parameter

[SnehasishChar]

try with \n after each parameter

Still not working. @lperron

[lperron]

This is the code. You can try to reverse engineer what it parses :-) PS: we did not write it. This is an external contribution. ```c++ bool XpressInterface::SetSolverSpecificParametersAsString( const std::string& parameters) { if (parameters.empty()) return true; std::vector<std::pair<std::string, std::string> > paramAndValuePairList; std::stringstream ss(parameters); std::string paramName; while (std::getline(ss, paramName, ' ')) { std::string paramValue; if (std::getline(ss, paramValue, ' ')) { paramAndValuePairList.push_back(std::make_pair(paramName, paramValue)); } else { LOG(ERROR) << "No value for parameter " << paramName << " : function " << __FUNCTION__ << std::endl; return false; } } ScopedLocale locale; for (auto& paramAndValuePair : paramAndValuePairList) { setParamIfPossible_MACRO(mapIntegerControls_, XPRSsetintcontrol, std::stoi); setParamIfPossible_MACRO(mapDoubleControls_, XPRSsetdblcontrol, std::stod); setParamIfPossible_MACRO(mapStringControls_, XPRSsetstrcontrol, stringToCharPtr); setParamIfPossible_MACRO(mapInteger64Controls_, XPRSsetintcontrol64, std::stoll); LOG(ERROR) << "Unknown parameter " << paramName << " : function " << __FUNCTION__ << std::endl; return false; } return true; } ```

[pet-mit]

Hello @SnehasishChar
This was happening because OPTIMALITYTOL & FEASTOL were set by the MPSolverParameters object, which overrides the solver-specific parameters (in current released versions).
It has been fixed here: #4244, so still not released. It will be fixed in the next version of or-tools.
Meanwhile, you can use MPSolverParameters.primalTolerance to set FEASTOL, and MPSolverParameters.dualTolerance to set OPTIMALITYTOL.

Here is an example in Java :

solver.setSolverSpecificParametersAsString(solverParams);
MPSolverParameters params = new MPSolverParameters();
params.setDoubleParam(MPSolverParameters.DoubleParam.PRIMAL_TOLERANCE, eps1); // FEASTOL
params.setDoubleParam(MPSolverParameters.DoubleParam.DUAL_TOLERANCE, eps2); // OPTIMALITYTOL
solver.solve(params);

Hope this helps!

PS: this is currently true for all XPRESS parameters that can be set through MPSolverParameters, not only these 2

@lperron I just saw this, don't hesitate to tag us next time :)