Use popcnt intrinsic for bitcount #1011
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Profiling of the test suite showed a large amount of time (nearly 1/3) devoted to computing of bitcounts used as checksums for diagnostics. This patch replaces the bit loop with the popcnt intrinsic, which produces the same result and uses the hardware assembly instruction when available (e.g. popcnt in x86). This change appears to have reduced the runtime of the test suite from 4.5 minutes to under 3 minutes.
Codecov Report
@@ Coverage Diff @@
## dev/gfdl #1011 +/- ##
============================================
+ Coverage 40.49% 43.16% +2.66%
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Files 213 213
Lines 62355 62352 -3
============================================
+ Hits 25253 26915 +1662
+ Misses 37102 35437 -1665
Continue to review full report at Codecov.
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It looks like total test time dropped from 14.5 to 12 minutes. Still dominated by other stuff (VM boot, building (esp. FMS), CodeCov uploads, etc). But this seems like an improvement. Gaea regression testing: https://gitlab.gfdl.noaa.gov/ogrp/MOM6/pipelines/9072 |
adcroft
approved these changes
Oct 1, 2019
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Gaea tests have passed. |
adcroft
approved these changes
Oct 1, 2019
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Profiling of the test suite showed a large amount of time (nearly 1/3)
devoted to computing of bitcounts used as checksums for diagnostics.
This patch replaces the bit loop with the popcnt intrinsic, which
produces the same result and uses the hardware assembly instruction when
available (e.g. popcnt in x86).
Note that popcnt is a Fortran 2008 feature.
This change appears to have reduced the runtime of the test suite from
4.5 minutes to under 3 minutes.