# 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.