ILOG CPLEX 11.0 User's Manual > Advanced Programming Techniques > Using Optimization Callbacks > Query or Diagnostic Callbacks

Query or diagnostic callbacks allow you to monitor an ongoing optimization, and optionally to abort it (that is, to terminate it). Query callbacks access more detailed information about the current optimization than do informational callbacks. As a side effect, query or diagnostic callbacks may slow progress. Furthermore, query or diagnostic callbacks make assumptions about the traversal of a conventional branch &  cut tree; those assumptions about a mixed integer program (MIP) may be incorrect during during dynamic search or during deterministic search in parallel optimization. For more detail about this point, see Query Callbacks and Dynamic Search and Query Callbacks and Deterministic Parallel Search.