- 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>
The 2668-entry table read off the black-box oracle's output is gone.
arw6_curve.rs now builds the 4096-entry table at first use from our own
measurement: piecewise linear through knots u_k = 128 k, c_k = u_k for
k <= 11 and 356.89 + 655.646 ln(k - 6) above, rounded half up, fitted to
the 7 same-exposure lossless (LJ92) / ARW6 pairs of the CC0 ILCE-7RM6 set.
A unit test pins the whole table (sum 27776336, weighted 92792980288),
its anchors, the identity through 1408 and strict monotonicity.
The corpus sums become regression values of the new output; the 12-bit
codes before the curve stay verified against the oracle (Phase 0).
docs/arw6-compression.md describes the curve, how it was measured, its
uncertainty, the structure and x2-scale evidence, why it is not in the
file, and the after-the-fact comparison with the oracle's curve; the
tracker and docs no longer call the output bit-exact against LibRaw.
Co-Authored-By: Claude <noreply@anthropic.com>
docs/superpowers/ held the working spec and plan, which pointed at the
local plan/ folder. The ARW6 module docs now cite the sections of
docs/arw6-compression.md, which gains the facts they relied on from the
spec: the NP field of word 0, the stream header word layout and how the
first half's residual lines are counted.
Co-Authored-By: Claude <noreply@anthropic.com>
`cargo xtask corpus --download` now fetches one full-frame Compressed and
one APS-C Compressed HQ file (about 94 MB) instead of all 12 (about
630 MB); the corpus test checks those two and the lossless-sibling
regression test is gone, since nothing would download those files.
docs/arw6-compression.md keeps the full table with source paths and
SHA-256, says which two xtask fetches and how to fetch the rest with
`curl -L`, and records the CC0 1.0 statement of RawDB's set record
(accessed 2026-10-10).
Co-Authored-By: Claude <noreply@anthropic.com>
The RawDB entries in xtask carry their SHA-256 as the third field, which
`cargo xtask corpus --download` checks; the corpus test keeps only the
sensor sum checks.
Co-Authored-By: Claude <noreply@anthropic.com>
