Monitoring Progress - Logging and Callbacks#

void GRBmsg(GRBenv *env, const char *message)#

Write a message to the console and the log file.

Arguments:

  • env – The environment whose log file should receive the message.

  • message – The message to be written.

Note

This call has no effect unless the OutputFlag parameter is set. In addition, it is ignored from within a MESSAGE callback (see WHERE values) and logging callback. The console logging can be controled with LogToConsole.

Example:
error = GRBmsg(env, "Add this message to the log");
int GRBsetcallbackfunc(GRBmodel *model, int (*cb)(GRBmodel *model, void *cbdata, int where, void *usrdata), void *usrdata)#

Set up a user callback function. Note that a model can only have a single callback method, so this call will replace an existing callback. To disable a previously set callback, call this function with a cb argument of NULL.

When solving a model using multiple threads, the user callback is only ever called from a single thread, so you don’t need to worry about the thread-safety of your callback.

A few parameters are callback settable. These parameters can be modified from within a callback call using GRBcbsetdblparam, GRBcbsetintparam, GRBcbsetstrparam, or GRBcbsetparam depending on the parameter type.

Return value:

A non-zero return value indicates that a problem occurred while setting the user callback. Refer to the Error Codes table for a list of possible return values. Details on the error can be obtained by calling GRBgeterrormsg.

Arguments:

  • model – The model in which the callback should be installed.

  • cb – A function pointer to the user callback function. The callback will be called regularly from the Gurobi Optimizer. The where argument to the callback function will indicate where in the optimization process the callback was invoked. Possible values are described in the Callback Codes section. The user callback can then call a number of routines to retrieve additional details about the state of the optimization (e.g., GRBcbget), or to inject new information (e.g., GRBcbcut, GRBcbsolution). The user callback function should return 0 if no error was encountered, or it can return one of the Gurobi Error Codes if the user callback would like the optimization to stop and return an error result.

  • usrdata – An optional pointer to user data that will be passed back to the user callback function each time it is invoked (in the usrdata argument).

Example:
int mycallback(GRBmodel *model, void *cbdata, int where, void *usrdata);
error = GRBsetcallbackfunc(model, mycallback, NULL);
int GRBgetcallbackfunc(GRBmodel *model, int (**cb)(GRBmodel *model, void *cbdata, int where, void *usrdata))#

Retrieve the current user callback function.

Return value:

A non-zero return value indicates that a problem occurred while retrieving the user callback. Refer to the Error Codes table for a list of possible return values. Details on the error can be obtained by calling GRBgeterrormsg.

Arguments:

  • model – The model in which the callback should be installed.

  • cb – A function pointer to the user callback function.

Example:
int (*mycallback)(GRBmodel *model, void *cbdata, int where, void *usrdata);
error = GRBgetcallbackfunc(model, &mycallback);
int GRBcbget(void *cbdata, int where, int what, void *resultP)#

Retrieve additional information about the progress of the optimization. Note that this routine can only be called from within a user callback function.

Return value:

A non-zero return value indicates that a problem occurred while retrieving the requested data. Refer to the Error Codes table for a list of possible return values. Details on the error can be obtained by calling GRBgeterrormsg.

Arguments:

  • cbdata – The cbdata argument that was passed into the user callback by the Gurobi Optimizer. This argument must be passed unmodified from the user callback to GRBcbget().

  • where – The where argument that was passed into the user callback by the Gurobi Optimizer. This argument must be passed unmodified from the user callback to GRBcbget().

  • what – The data requested by the user callback. Valid values are described in the Callback Codes section.

  • resultP – The location in which the requested data should be placed.

Example:
if (where == GRB_CB_MIP) {
  double nodecount;
  error = GRBcbget(cbdata, where, GRB_CB_MIP_NODECNT, (void *) &nodecount);
  if (error) return 0;
  printf("MIP node count is %d\n", nodecount);
}
void GRBversion(int *majorP, int *minorP, int *technicalP)#

Return the Gurobi library version number (major, minor, and technical).

Arguments:

  • majorP – The location in which the major version number should be placed. May be NULL.

  • minorP – The location in which the minor version number should be placed. May be NULL.

  • technicalP – The location in which the technical version number should be placed. May be NULL.

Example:
int major, minor, technical;
GRBversion(&major, &minor, &technical);
printf("Gurobi library version %d.%d.%d\n", major, minor, technical);