PDG - A PROCESS-LEVEL DEBUGGER FOR CONCURRENT PROGRAMS IN THE GRAPE PARALLEL PROGRAMMING ENVIRONMENT

In this paper, we describe the process-level debugger of GRAPE, our hi erarchical graphical programming environment for concurrent programs. Its unique feature is that it clearly separates the identification of erroneous processes, which we call process-level debugging, from the e xact localisation of the bug at the source-level. This divide-and-conq uer approach is absolutely necessary for debugging complex parallel pr ograms in a fast and systematic way. Our process-level debugging appro ach is based on an animation of the program's behaviour on its hierarc hical graphical representations. Graphical views are used that reflect the programmer's mental picture of the actual application. Hierarchy allows us to employ a top-down debugging approach in which we successi vely refine the search-space by zooming in on suspect processes first- time-right. During animation a debugging kernel implementing a record- replay mechanism guarantees reproducible behaviour.