Is it me, or is it the machine?

Sometimes programmers do a good job but the execution does not report the expected performance. The first step to improve the performance is to understand what’s going on, and flexible tools like Paraver are key to face unknown problems that can be anywhere. During the tools trainings I use to ask for a code from the attendees to be used for the demo, but sometimes no example is provided. In these cases, I run the Lulesh benchmark. As a result, I have collected Paraver traces of Lulesh running on many different systems. The talk will present the high variability I have observed on the achieved performance with the same source code, as well as the ability of our performance tools to pinpoint what is causing the loose of performance.