- The vertical inverse 5/3 lifts whole rows at once (`inverse_lift` with samples `w` values wide)
instead of gathering each column through a strided iterator and scattering it back: the same
integer arithmetic, sequential memory. The horizontal pass is the same function with w = 1.
- `0^n 1` codes are counted with one `leading_zeros` over the next MAX_DPT + 1 bits instead of bit by
bit (same bits consumed, same errors); each line reserves its values up front.
- Colour reconstruction reads plane rows as slices and runs over rows in parallel (it was one
thread per tile: 4 threads on a full-frame file whatever the machine).
Best of 5 on 4 CPUs, previous and new decoder alternating: ILCE-7RM6 FF HQ 0.56 → 0.46 s,
FF Compressed 0.54 → 0.38 s, APS-C HQ 0.34 → 0.23 s, APS-C Compressed 0.35 → 0.24 s
(docs/arw6-compression.md → Timings). The decoded mosaic is identical (hash of every sample) on
the 8 ARW6 corpus files and 2 private full-frame photos (ISO 100, ISO 12800); the pinned corpus
sums still match.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
