CPXXsetinfocallbackfunc and CPXsetinfocallbackfunc

Description

The routine CPXXsetinfocallbackfunc/CPXsetinfocallbackfunc sets the user-written callback routine that CPLEX calls regularly during the optimization of a mixed integer program and during certain cut generation routines.

This routine enables the user to create a separate callback function to be called during the solution of mixed integer programming problems (MIPs). Unlike any other callback routines, this user-written callback function only retrieves information about MIP search. It does not control the search, though it allows the search to terminate. The user-written callback function is allowed to call only two other routines: CPXXgetcallbackinfo/CPXgetcallbackinfo and CPXXgetcallbackincumbent/CPXgetcallbackincumbent.

The prototype for the callback function is identical to that of CPXXsetmipcallbackfunc/CPXsetmipcallbackfunc.

Arguments

env

A pointer to the CPLEX environment, as returned by CPXXopenCPLEX/CPXopenCPLEX.

callback

A pointer to a user-written callback function. Setting callback to NULL will prevent any callback function from being called during optimization. The call to callback will occur after every node during optimization and during certain cut generation routines. This function must be written by the user. Its prototype is explained in the Callback description.

cbhandle

A pointer to user private data. This pointer will be passed to the callback function.

Return

Example

 status = CPXsetinfocallbackfunc (env, mycallback, NULL);

Callback description

 int CPXPUBLIC
 callback (CPXCENVptr env,
           void *cbdata,
           int wherefrom,
           void *cbhandle);
 

This is the user-written callback routine.

Callback return value

A nonzero return value terminates the optimization. That is, if the user-written callback function returns nonzero, it signals that CPLEX should terminate optimization.

Callback arguments

env

A pointer to the CPLEX environment that was passed into the associated optimization routine.

cbdata

A pointer passed from the optimization routine to the user-written callback function that identifies the problem being optimized. The only purpose for the cbdata pointer is to pass it to the routine CPXXgetcallbackinfo/CPXgetcallbackinfo.

wherefrom

An integer value reporting from which optimization algorithm the user-written callback function was called. Possible values and their meaning appear in the table.

cbhandle

A pointer to user private data as passed to CPXXsetinfocallbackfunc/CPXsetinfocallbackfunc.