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slcs-jsc / mptrac

Massive-Parallel Trajectory Calculations (MPTRAC) is a Lagrangian particle dispersion model for the analysis of atmospheric transport processes in the free troposphere and stratosphere.
GNU General Public License v3.0
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Performance degradation with Stage 2024 on JUWELS Booster? #22

Closed lars2015 closed 10 months ago

lars2015 commented 1 year ago

Describe the bug

MPTRAC nightly builds (https://datapub.fz-juelich.de/slcs/mptrac/nightly_builds/) show that the runtime of the physics timers on JUWELS Booster significantly increased on 3 Nov 2023, when the new stage 2024 was enabled. Switching back to stage 2023 on 10 Nov reproduced the original runtime:

plot_phys

Additionally, the new stage causes an issue in gpu_test sample.tab output:

Bildschirmfoto vom 2023-11-10 08-04-13

To Reproduce

Rerun the test case at: /p/fastdata/slmet/slmet111/model_data/mptrac/nightly_builds/juwels-booster/run.sh

Expected behavior

Need to further investigate this issue and find the root cause.

Maybe next to updating the software stage also other changes of the JUWELS Booster system config were introduced?

lars2015 commented 10 months ago

The performance degradation was found to be related to an issue with the new version of the NVIDIA C compiler applying vectorization to a specific loop in module_mixing_help() that was prevented in the previous version.

The problem has been fixed by manually disabling vectorization for the loop:

https://github.com/slcs-jsc/mptrac/blob/a50a0581cb1df2a3ab1f4c8559330b9418d248b9/src/trac.c#L2013