Symmetry

2026-05-27 09:33:36 +02:00
parent bd371cd8e5
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+# Optimization: SoA (float version)
+
+- **Author**: Smail
+- **Predecessor**: variant_float_inlining_SoA.cpp
+- **File(s)**: variants/variant_float_inlining_SoA_symmetry.cpp
+- **Status**: TBD
+
+## What this changes
+
+Implemented a LUT for calculating the distances since they are symmetric. Saves n_p/2 sqrt
+
+## Code (relevant snippet)
+
+
+See `variants/variant_float_inlining_SoA.cpp`.
+
+## Benchmark
+
+Conditions: min of N runs (TBD), N_ITER=1000, -O3 -march=native -flto.
+Diff is vs `variant_float_inlining`.
+
+### x86
+
+**Machine**: TBD
+
+**Frequency**: TBD
+
+| N    | W(n) [Flops] | T(n) [Cycles] | Performance [Flops/Cycle] | Diff vs Predecessor |
+| ---- | ------------ | ------------- | ------------------------- | ------------------- |
+| 50   |              |               |                           |                     |
+| 100  |              |               |                           |                     |
+| 200  |              |               |                           |                     |
+| 500  |              |               |                           |                     |
+
+### ARM (Apple)
+
+**Machine**: TBD
+
+**Frequency**: TBD
+
+| N    | W(n) [Flops] | T(n) [Cycles] | Performance [Flops/Cycle] | Diff vs Predecessor |
+| ---- | ------------ | ------------- | ------------------------- | ------------------- |
+| 50   |              |               |                           |                     |
+| 100  |              |               |                           |                     |
+| 200  |              |               |                           |                     |
+| 500  |              |               |                           |                     |
+
+## Analysis
+
+Layout change only, so the expectation is roughly no win on its own. The
+float scalar loop already auto-vectorises in pieces with `-O3
+-march=native`, so SoA doesnt buy much over what the AoS version was
+already doing. The real payoff lands in the AVX2 child.
+
+Verify passes against `baseline_float_n60_i500.csv` (from
+`variant_float_baseline`) at the 1cm tolerance.
+
+## Takeaway
+
+Setup step for the AVX2 variant.