Algorithm choice and parameter settings

The performance of the underlying solution algorithm has, strictly speaking, nothing to do with the efficiency of Mosel. But for completeness' sake the reader may be reminded that the subroutines getparam and setparam can be used to access and modify the current settings of parameters of Mosel and also those provided by modules, such as solvers.

The list of parameters defined by a module can be obtained with the Mosel command

With Xpress Optimizer (module mmxprs) you may try re-setting the following control parameters for the algorithm choice:

• LP: XPRS_PRESOLVE
• MIP: XPRS_PREPROBING, XPRS_MIPPRESOLVE, XPRS_CUTSTRATEGY, XPRS_HEURSTRATEGY, XPRS_SBEFFORT, XPRS_NODESELECTION
• Other useful parameters are the criteria for stopping the MIP search: XPRS_MAXNODE, XPRS_MAXMIPSOL, XPRS_MAXTIME, the cutoff value (XPRS_MIPADDCUTOFF, XPRS_MIPABSCUTOFF), and various tolerance settings (e.g. XPRS_MIPTOL).

Refer to the Xpress Optimizer Reference Manual for more detail.

You may also add priorities or preferred branching directions with the procedure setmipdir (documented in the chapter on mmxprs in the Mosel Reference Manual).