Score-P and OMPT: Navigating the perils of callback-driven parallel runtime introspection

Abstract

Event-based performance analysis aims at modeling the behavior of parallel applications through a series of state transitions during execution. Different approaches to obtain such transition points for OpenMP programs include source-level instrumentation (e.g., OPARI) and callback-driven runtime support (e.g., OMPT). In this paper, we revisit a previous evaluation and comparison of OPARI and an LLVM OMPT implementation—now updated to the OpenMP 5.0 specification—in the context of Score-P. We describe the challenges faced while trying to use OMPT as a drop-in replacement for the existing instrumentation-based approach and the changes in event order that could not be avoided. Furthermore, we provide details on Score-P measurements using OPARI and OMPT as event sources with the EPCC and SPEC OpenMP benchmark suites.