Matrix files

If the optimization process with Xpress Optimizer is started from within a Mosel program, or if the solving procedure is part of the application into which a Mosel model has been embedded, then the problem matrix is loaded in memory into the solver without writing it out to a file (which would be expensive in terms of running time). However, in certain cases it may still be required to be able to produce a matrix. With Xpress, the user has the choice between two matrix formats: extended MPS and extended LP format, the latter being in general more easily human-readable since constraints are printed in algebraic form.

With Mosel, there are several possibilities for generating a matrix:

1. With a matrix generation statement in the model file:
   to create an MPS matrix for our problem add the line

     exportprob(EP_MPS, "folio", Return)

   for an LP format matrix (which we intend to maximize at some point) add the line

     exportprob(EP_MAX, "folio", Return)

   immediately before or instead of the optimization statement.
2. From a Java application after having executed the model file:
   

     XPRMModel model;
     model.exportProblem("m", "folio");

   This will output the matrix in MPS format. To print with LP format change the first argument of exportProblem:

     model.exportProblem("p", "folio");