AIMMS Solver Configuration

The trivial approach to change which solver should be used for each type of problem is to make use of the Solver Configuration screen. You can access this configuration screen via Menu > Settings > Solver Configuration…

The picture above shows an example screenshot, where CPLEX 12.4 is used as the default solver for problems of the type LP. By double-clicking on any of the X’s in the LP column, you can make the corresponding solver the default for LP problems. Any changes you make to the default solvers via this configuration screen are persistent between your AIMMS sessions: if you close your AIMMS application and start it again, the same default settings are used.

Alternatively, you can modify the default solvers programmatically in an AIMMS procedure. You can do so by modifying the contents of the predefined AIMMS element parameter CurrentSolver. This element parameter is indexed over the IndexMathematicalProgrammingTypes and has the range AllSolvers. This means that for each mathematical program type, you can select one solver.

Changes made to this element parameter are not persistent, meaning you will loose any changes you made to it after closing AIMMS if you do not store it yourself. Note that the element parameter CurrentSolver is not stored when saving a case.

To change the default solver for LP problems to GUROBI 5.0 for all subsequent solve statements, you can use the following code in a procedure:

if StringToElement(AllSolvers, "GUROBI 5.0") then
	CurrentSolver('LP') := StringToElement(AllSolvers, "GUROBI 5.0") ; 
else
	raise error "Solver GUROBI 5.0 is not present" ; 
endif ;

Note that I am using the function StringToElement to avoid using single quoted elements (e.g. ‘GUROBI 5.0′). This way, opening the AIMMS project will not result in a compilation error in case GUROBI 5.0 is not present in the set AllSolvers.

Please keep in mind that the values of CurrentSolver are used as defaults: You can also still override these defaults for each separate solve statement in the following way:

!Solve TransportModel Math Program with the solver CPLEX 12.2 regardless
!of what the default solver for this problem type is.
solve TransportModel where solver:='CPLEX 12.2' ;