Visualization of message passing parallel programs with the TOPSYS parallel programming environment

Parallel programming is orders of magnitudes more complex than writing sequential programs. This is particularly true for programming distributed memory multiprocessor architectures based on message passing programming models. Apart from understanding the sequential parts of the parallel program, new degrees of freedom lead to additional problems. Understanding the synchronization and communication behavior of parallel programs is the most critical issue in programming distributed memory multiprocessors. The paper describes methods and tools for visualization and animation of the dynamic execution of parallel programs. Based on an evaluation and classification of existing visualization environments, the visualization and animation tool VISTOP (VISualization TOol for Parallel Systems) is presented as part of the integrated tool environment TOPSY S (TOols for Parallel SYStems) for programming distributed memory multiprocessors. VISTOP supports the interactive on-line visualization of message passing programs based on various views; in particular, a process graph based concurrency view for detecting synchronization and communication bugs.