The Callable Library supports callbacks so that you can define functions that will be called at crucial points in your application:

• during the presolve process;

• once per iteration in a linear programming routine;

• once before a node is processed in a mixed integer optimization (if the end-user is licensed for the ILOG CPLEX Mixed Integer Optimizer).

In addition, callback functions can call CPXgetcallbackinfo() to retrieve information about the progress of an optimization algorithm. They can also return a value to indicate whether an optimization should be aborted. CPXgetcallbackinfo() is the only routine of the Callable Library that a user-defined callback may call. (Of course, calls to routines not in the Callable Library are permitted.)

Using Callbacks describes callback facilities in greater detail.