Add Mfprelaxed to NVHPC builds#1651
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Pull request overview
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Adds the NVHPC Fortran compiler flag -Mfprelaxed to mitigate a performance regression introduced in NVHPC 24.7 affecting WENO/Riemann kernels.
Changes:
- Enable
-Mfprelaxedfor NVHPC Fortran compilation via CMake generator expressions.
sbryngelson
previously approved these changes
Jul 17, 2026
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #1651 +/- ##
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- Coverage 60.95% 59.57% -1.39%
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Files 83 83
Lines 20003 21111 +1108
Branches 2983 3128 +145
==========================================
+ Hits 12193 12576 +383
- Misses 5782 6433 +651
- Partials 2028 2102 +74 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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sbryngelson
approved these changes
Jul 17, 2026
Member
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good job |
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Description
This PR adds the
Mfprelaxesflag to NVHPC builds to fix a code-gen change in NVHPC 24.7 that caused a slowdown in the WENO and Riemann kernels. See https://forums.developer.nvidia.com/t/nvfortran-openacc-performance-regression-weno5-reconstruction-kernel-1-7x-slower-since-24-7-24-5-good-24-7-first-bad/376982 for details.Type of change (delete unused ones)
Testing
Relying on CI for testing. This change demonstrated the expected performance improvement with
examples/3D_performance_test.AI code reviews
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