Run-Time Analysis and Instrumentation for Communication Overlap Potential

Blocking communication can be runtime optimized into non-blocking communication using memory protection and replacement of MPI functions. All such optimizations come with overhead, meaning no automatic optimization can reach the performance level of hand-optimized code.In this paper, we present a method for using previously published runtime optimizers to instrument a program, including measured speedup gains and overhead.The results are connected with the program symbol table and presented to the user as a series of source code transformations. Each series indicates which optimizations were performed and what the expected saving in wallclock time is if the optimization is done by hand.