APM.SOLVER - APMonitor Option

 Type: Integer, Input
 Default Value: 3
 Description: Solver options
              0 = Benchmark All Solvers
              1-5 = Available Solvers Depends on License

SOLVER selects the solver to use in an attempt to find a solution. There are free solvers: 1: APOPT, 2: BPOPT, 3: IPOPT distributed with the public version of the software. There are additional solvers that are not included with the public version and require a commercial license. IPOPT is generally the best for problems with large numbers of degrees of freedom or when starting without a good initial guess. BPOPT has been found to be the best for systems biology applications. APOPT is generally the best when warm-starting from a prior solution or when the number of degrees of freedom (Number of Variables - Number of Equations) is less than 2000. APOPT is also the only solver that handles Mixed Integer problems. Use option 0 to compare all available solvers.

Options for solvers can be set using configuration parameters such as MAX_ITER or else by creating an options file such as ipopt.opt or apopt.opt. Below is an example of setting options for the APOPT solver for a mixed integer nonlinear programming solution. The File...End File section creates a new apopt.opt file when APMonitor compiles the model file.

 File apopt.opt
   minlp_maximum_iterations 10000 
   minlp_max_iter_with_int_sol 500 
   minlp_as_nlp 1 
   minlp_branch_method 3 
   minlp_gap_tol 1.0e-2 
   minlp_integer_tol 1.0e-2 
   minlp_integer_max 2.0e9 
   minlp_integer_leaves 1 
   minlp_print_level 1 
   nlp_maximum_iterations 500 
   objective_convergence_tolerance 1.0e-6 
   constraint_convergence_tolerance 1.0e-6 
 End File

Refer to Options for apopt.opt for additional details for the APOPT solver and Options for ipopt.opt for additional details for the IPOPT solver.