Visualization of Affect-Relations of Message Races for Debugging MPI Programs

Detecting unaffected races is important for debugging MPI parallel programs, because unaffected races can cause the occurrence of affected races which do not need to be debugged. However, the previous techniques can not dis- cern unaffected races from affected races so that program- mers will be easily overwhelmed by the vast information of race detection. In this paper, we present a new visualiza- tion which lets programmers know which race is affected or not. For this, our technique checks whether any message racing toward a race is affected or not based on happen- before relation, and also checks which process influences a race during an execution. After the execution, it visualizes the affect-relations of the detected races. Therefore, our vi- sualization helps for programmers to effectively distinguish unaffected races from affected races, and to debug MPI par- allel programs.