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Further performance improvements for FP math#905

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isaacbrodsky merged 6 commits intouber:masterfrom
heshpdx:master
Sep 19, 2024
Merged

Further performance improvements for FP math#905
isaacbrodsky merged 6 commits intouber:masterfrom
heshpdx:master

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@heshpdx heshpdx commented Sep 9, 2024

I was requested to dig further in the spirit of !852 so I spent time inspecting other parts of the code. This PR unlocks more FDIV->FMUL opportunities. I inspected the assembly and confirmed that each of the changes did result in a transformation of FDIV to FMUL.

Here are the perf outliers, with the majority of other tests in the noise (since likely they do not exercise the changed code).

Grid path cells shows 4.3% upside, as measured on a Ampere Altra in the OCI Cloud, using gcc-10 out of the box. Regular h3 cmake build.
mainline:

$ ./build/bin/benchmarkGridPathCells 
        -- gridPathCellsNear: 39.136827 microseconds per iteration (10000 iterations)
        -- gridPathCellsFar: 1799.592192 microseconds per iteration (1000 iterations)

branch:

$ ./build_fast/bin/benchmarkGridPathCells 
        -- gridPathCellsNear: 37.556445 microseconds per iteration (10000 iterations)
        -- gridPathCellsFar: 1724.603344 microseconds per iteration (1000 iterations)

The experimental polygon to cells overlapping is also an outlier, 1-2%:

mainline:

        -- polygonToCellsSF_Overlapping: 5817.474534 microseconds per iteration (500 iterations)
        -- polygonToCellsAlameda_Overlapping: 13169.533630 microseconds per iteration (500 iterations)
        -- polygonToCellsSouthernExpansion_Overlapping: 381815.775600 microseconds per iteration (10 iterations)

branch:

        -- polygonToCellsSF_Overlapping: 5773.028512 microseconds per iteration (500 iterations)
        -- polygonToCellsAlameda_Overlapping: 12886.969474 microseconds per iteration (500 iterations)
        -- polygonToCellsSouthernExpansion_Overlapping: 377545.843300 microseconds per iteration (10 iterations)

@heshpdx
Further performance improvements for FP math
4604d1f 
More FDIV->FMUL opportunities unlocked, following in the
spirit of #852
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coveralls commented Sep 9, 2024 •
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Coverage Status

coverage: 98.824% (-0.002%) from 98.826%
when pulling b7542c3 on heshpdx:master
into a1037eb on uber:master.

nrabinowitz
nrabinowitz approved these changes Sep 10, 2024
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Thanks for these optimizations!

@heshpdx @nrabinowitz
Update src/h3lib/lib/localij.c
dd45fbe 
Co-authored-by: Nick Rabinowitz <public@nickrabinowitz.com>
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heshpdx commented Sep 18, 2024

Looks like the CIFuzz is broken. Do we need to update that runner?

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isaacbrodsky commented Sep 18, 2024

Looks like the CIFuzz is broken. Do we need to update that runner?

I'm addressing it in #907. You may need to rebase or merge that change in too

@isaacbrodsky isaacbrodsky merged commit 4899d29 into uber:master Sep 19, 2024
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@nrabinowitz nrabinowitz nrabinowitz approved these changes

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