What to Draw? When to Draw? An Essay on Parallel Program Visualization

Parallel programs are difficult to understand and the research community is determined to provide tools to help improve that understanding. As a result, there is intense interest in using visualization to understand the execution of parallel programs. But visualization is like the surgeon’s knife: properly used it will quickly cut to the essentials; improper use brings colorful but disastrous results. The results from a visualization are almost always visually appealing, but I claim that they only occasionally are useful in debugging a program or improving its performance.