Anders Olsson f0d6211387 perf(game): revert Task 10 SmallVec changes — caused sequential regression ...

The Vec<Vec<_>> → SmallVec<[SmallVec<[_;8]>;8]> change in Task 10
regressed Batch::iteration from 23.29 µs to 29.73 µs (+28%). The
SmallVec was motivated by reducing parallel-path allocations but
it hurt the sequential path substantially.

Reverting game.rs + time_slice.rs + history.rs storage back to the T2
Vec<Vec<_>> shape. The parallel rayon path (unsafe direct-write +
thread_local ScratchArena + RAYON_THRESHOLD=64 fallback) stays — it
is independent of Game's internal storage.

Benchmarks after revert:
  Batch::iteration (seq, no rayon): 23.23 µs (restored ≈T2)
  Batch::iteration (rayon):         24.57 µs
  history_converge/500x100@10:       4.03 ms seq,  4.24 ms rayon — 1.0×
  history_converge/2000x200@20:     20.18 ms seq, 19.82 ms rayon — 1.0×
  history_converge/1v1-5000x50000@5000: 11.88 ms seq, 9.10 ms rayon — 1.3×

Part of T3.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

2026-04-24 14:55:37 +02:00

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