Dehaze cost 22.9 ms of a 2560x1600 frame on the reference laptop RTX 3050,
and 54.1 ms at 3840x2160, with the memory clock held at 810 MHz by the power
cap (graphics 1762 MHz). It ran five passes: a run and a span erosion along
x, the same along y, and the recovery. At those clocks a detail pass costs
what it reads and writes, not what it taps: a pass with an empty body -
one render-sized rgba16float read and write - measured 4.0 ms, and each
dehaze pass 4.4-4.6 ms, so the taps were about 2 ms of the 22 and the four
hand-offs between passes were the rest.
Each axis is now one pass that takes the minimum over the whole window
directly, and the recovery rides in the y pass, which already holds the
veil and the pixel's own colour. That is 36 texture reads per pixel at
2560x1600 in place of 12, nearly all of them cache hits, and two passes in
place of five.
The picture is the same bits. A minimum is exact in any order, and the
window is the one Split always covered, the surplus pixel on the far side
included (Split::first and Split::width). The veil crossing the removed
hand-offs was already exactly representable in rgba16float - a minimum of
channels read from rgba16float, floored at zero - so storing it between
passes never rounded anything that the fused form now keeps unrounded.
Measured with a scratch probe that renders the synthetic 60 MP frame from
examples/frame_budget.rs, only a detail parameter moving so the fused pass
is reused, 30 frames per scene after six of warm-up, five runs of each
binary alternated, median of the per-run p50:
scene before after
dehaze 2560 fit 22.88 ms 9.06 ms
dehaze 2560 1:1 23.41 ms 9.52 ms
dehaze 3840 fit 54.09 ms 28.12 ms
all detail 2560 fit 53.11 ms 39.97 ms (NR, sharpen, clarity,
all detail 2560 1:1 67.48 ms 56.42 ms texture, dehaze)
every op 2560 fit 57.59 ms 44.19 ms (with film)
every op 2560 1:1 71.83 ms 57.93 ms
controls without dehaze (NR, sharpen, clarity, texture): within +-2%
The rgba8 output hashed identically before and after for every scene -
dehaze alone, all five detail operations, every operation with film, and
each other detail operation alone - at fit and 1:1, at 2560x1600,
3840x2160, 1917x1203 and 333x211: 64 of 64.
dtourolle
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