Documentation

C Parameter Examples

The C interface defines a symbolic constant for each parameter. The symbolic constant name is prefixed by GRB_type_PAR_, where type is either INT, DBL, or STR. This is followed by the capitalized parameter name. For example, the symbolic constant for the integer Threads parameter (found in C header file gurobi_c.h) is:

#define GRB_INT_PAR_THREADS "Threads"

The routine you use to modify a parameter value depends on the type of the parameter. For a double-valued parameter, you would use GRBsetdblparam.

Note that a model gets its own copy of the environment when it is created. Changes to the original environment have no effect on the copy, and vice versa. Use GRBgetenv to retrieve the environment associated with a model if you would like to change the parameter value for that model.

To set the TimeLimit parameter for a model, you'd do:

  error = GRBsetdblparam(GRBgetenv(model), GRB_DBL_PAR_TIMELIMIT, 100.0);

If you'd prefer to use a string for the parameter name, you can also do:

  error = GRBsetdblparam(GRBgetenv(model), "TimeLimit", 100.0);

The case of the string is ignored, as are underscores. Thus, TimeLimit and TIME_LIMIT are equivalent.

Use GRBgetdblparam to query the current value of a (double) parameter:

  double currentvalue;
  error = GRBgetdblparam(modelenv, "TimeLimit", &currentvalue);