A scalable debugger for massively parallel message-passing programs

In a message-passing program, there are at least as many threads as processors, and the programmer must deal with large numbers of them on a massively parallel machine. On our target machine, the CM-5, we had previously developed Prism, a programming environment that supports debugging, data visualization, and performance analysis of data-parallel programs. We discuss how our new version, Node Prism, extends Prism's capabilities for message-passing programs. It looks and feels like the data-parallel version, but it uses new methods for user-debugger interaction that promote greater understanding of parallel programs. It offers scalable expression, execution, and interpretation of all debugging operations, making it easier to debug and understand message-passing programs.<<ETX>>