Originally posted by: joehuchette

Is there any way to force CPLEX to use the user callback I add to the model? I'm working on a Julia interface to CPLEX via the C API and am attempting to verify my code works as expected. However, at the moment I seem to add the user callback without error, but the callback does not seem to be invoked, even with moderately-sized problems. Is there a particular parameter configuration (or some other trick) that forces invocation of the user callback? Thanks. 

There is no way to force invocation of the cut callback since that is not needed. If a callback is installed then CPLEX will always invoke it at the appropriate stages of the solution process.

A cut callback will not be invoked if the problem is solved before the cut loop is entered, so what you need for testing is a model that does not solve at/before the root node. Does any of your test models go into the Branch-and-Bound phase? If you have a model for which CPLEX does Branch-and-Bound but does not invoke the cut callback, could you post the CPLEX log here?