Add configure-time CELERITAS_OPENMP switch to change threading
#1222
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sethrj
added
core
amandalund
approved these changes
May 7, 2024
Co-authored-by: Amanda Lund <alund@anl.gov>
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Event-level OpenMP was added in #774 to more accurately represent the behavior of Geant4 integration. Unfortunately we found that OpenMP isn't up to the task of efficiently threading both track-parallel and event-parallel (see also #1073). This adds a configure option to switch between track-level parallelism (inside a kernel) and event-level (for now, only in celer-sim). Since track-level parallelism isn't ideal for CPU (striding, integration, etc.) the default is set to event-level, and furthermore a warning is emitted at configure time if track-level parallelism is enabled alongside Geant4 MT (see #1056).
Supersedes #1220