Parallel program debugging with on-the-fly anomaly detection

An approach for parallel debugging that coordinates static analysis with efficient on-the-fly access anomaly detection is described. On-the-fly instrumentation mechanisms are being developed for the structured synchronization primitives of Parallel Computing Forum (PCF) Fortran, the emerging standard for parallel Fortran. The proposed instrumentation techniques guarantee that one can isolate schedule-dependent behavior in a schedule-independent fashion. The result is that a single-instrumented execution will either report sources of schedule-dependent behavior, or it will validate that all executions of the program on the same data compute the same result. When an instrumented execution is being used solely to find sources of schedule-dependent behavior, its cost can be reduced by slicing out computations that do not contribute to race conditions. Ongoing efforts to incorporate the proposed debugging approach in the ParaScope environment are described