[Coin-symphony] jssp.mod in glpk distribution

[Menal Guzelsoy]

Kendall,

Can you send me the mod file?

Menal.

Quoting Kendall Bailey <krbailey at gmail.com>:

> I'm working on an AMPL driver for the OSI interface, including the
> OsiSymSolverInterface.  I've used AMPL v9.1.2 to generate a binary
> problem file from the jssp.mod that's included with GLPK.  It's a job
> shop scheduling problem.  I can solve it with CPLEX,
> OsiCbcSolverInterface and OsiGlpkSolverInterface.  Each returns a
> slightly different solution, but all three find the optimal objective
> value to be 55.  When I try OsiSymSolverInterface, it claims to find a
> proven optimal solution, but the objective is 69.
>
> Since I've just substituted Sym in for Cbc or Glpk and found such
> different results, I thought I ask if there's known gotcha's for using
> OsiSymSolverInterface that might explain it.  Below is the code to do
> the solve, once the constraint matrix, objective and bounds are
> retrieved from the AMPL file.  Thanks for any help!
>
> (by the way, solve times were: cplex - 0.5sec, glpk - 1.5min, cbc - 1hour)
>
> I can supply the jssp.mod and/or jssp.nl.
>
> Thanks,
> Kendall
>
>
>   solver->loadProblem(*matrix,LUv,Uvx,objective,LUrhs,Urhsx);
>
>   for( int i = 0; i < numIntegerVars; ++i )
>   {
>      // continuous vars come first, followed by binary and then
>      // other integer vars.
>      solver->setInteger( numContinuousVars + i );
>   }
>
>   solver->initialSolve();
>   if( numIntegerVars )
>   {
>      // solve for integer vars if there are any
>      solver->branchAndBound();
>   }
>
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