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Description
This issue tracks my investigation into why mom5 is significantly slower when compiled with oneAPI. For starters, I compared the timings from the logfile.0000.out for two runs - the released config (with ifort, atmosphere layout 16x13, ocean layout 14x14) and one of the faster oneAPI versions that still used 416 cores (atmosphere layout 12x13, ocean layout 19x13)
Two functions (assuming the time for one doesn't include the other) - (Ocean shortwave) and (Ocean shortwave penetrate) together contribute to nearly 200 seconds of slowdown.
Here's the list of the functions that stood out as taking significantly more time with oneAPI:
Comparing the last 204 lines from logfile.00000.out
Generated from vimdiff'ing last_204_lines_ocean_logfile_000000_out_pr98-29-atm-layout-12x13-ocean-layout-19x13-cice4-12.txt and last_204_lines_ocean_logfile_000000_out_Jun20-released-config.txt in /g/data/tm70/ms2335/performance_optimisation_runs/classic/access-esm1p6/intel@19.0.3.199+target-x86-v4/sapphirerapids (or, via symlink, as /home/593/ms2335/perf-opt-classic-esm1.6/sapphirerapids)
| function | time with ifort | time with ifx |
|---|---|---|
| (Ocean update density) | 68.753486 | 130.024669 |
| (Ocean shortwave) | 23.124541 | 117.218480 |
| (Ocean surface flux) | 41.250250 | 189.090736 |
| (Ocean barotropic dynamics) | 46.788131 | 152.962205 |
| (Ocean diagnostics) | 62.194185 | 98.986182 |
| (Ocean tracer halo updates) | 275.070814 | 322.911296 |
| (Ocean sum ocean surface) | 88.946095 | 127.932427 |
| (Ocean tracer tmask limit) | 22.219161 | 82.341906 |
| (Ocean tracer: advection) | 233.915603 | 264.396445 |
| (Ocean generic tracer: source) | 781.969017 | 851.825148 |
| (Ocean neutral: diffuse) | 345.828021 | 418.568721 |
| (Ocean ndiffuse: fx-flux) | 64.232973 | 117.111274 |
| (Ocean ndiffuse: fy-flux) | 59.803690 | 109.397266 |
| (Ocean advect: MDFL-sweby-cui) | 37.223727 | 63.833007 |
| (Ocean shortwave penetrate) | 15.296601 | 103.740304 |
| (Ocean tracer_diag: total water | 5.859774 | 37.781129 |