Wrappers for Tracing Collective Communication Functions

Effectively and efficiently implementing parallel programs for computer systems with a large number of processing elements involves the investigation of occurring communication between processes. The communication entails messages that are passed between participating processing elements. Analysing, debugging and tuning of parallel programs is very complex due to the dynamic behaviour of the communication. Recording the communication events during the execution of a parallel program together with a time stamp assists a programmer in analysing the parallel program by enabling the reconstruction of the dynamic behaviour of the communication. An automatic instrumentation process changes the parallel program for recording all important events, including the communication events. In association with Cray Research the Zentralinstitut fur Angewandte Mathematik at the Forschungszentrum Ji.ilich implements an instrumentation module for the Performance Analysis Tool (PAT) for the Cray T3E parallel computer systems. Next to Point-to-Point communication, the collective communication functions of th