The pre-scan measured the spot width on all 60 frames of its sample every
time. The radius that measurement feeds is a three-way choice - R1ForWidth
moves only where 2*r80 crosses 4.5 and 5.5 - and 29 of 37 measurable
crystals sit more than 0.29 px clear of both switches, so most of the
sample is spent confirming a bucket the first few frames already picked.
Measure instead on a growing share of it - every eighth frame, then every
fourth, every second, all of it - and stop at the first tier whose answer
has settled: within 0.40 px of what the smaller sample said AND 0.25 px
clear of both switches. Both conditions are load-bearing. Clearance alone
loses the crystal whose r80 is 0.07 px from a switch, because its small
samples read across it; the step test alone lets a sample settle on a
switch and stop there. Both bounds sit interior to a two-dimensional
region that is right on 38 of 38, and every candidate was re-scored at all
eight phase offsets of the tier ladder.
The tiers are sized in worker-rounds rather than frames: a first tier of
five frames occupies eight workers as long as one of eight does. A {12,4,
2,1} ladder measures 11% fewer frames than {8,4,2,1} and is 11% slower.
Over the rotation battery this reads 1215 of 2280 frames - 21 crystals
stop at 15, 4 at 30, 13 still run all 60 - and the chosen r1 is identical
on 38 of 38, as is the beam-stop mask the reordered loop also touches.
The pass feeds nothing else into the run, so every merged intensity is
unchanged by construction and no battery is required. Cost over the
battery goes 15.6 s to 10.1 s, median 0.18 s to 0.14 s per data set.
Note for anyone optimising this further: the measurement itself is 0.54%
of the pre-scan's cycles. The cost is the decode, preprocessing and spot
finding each frame needs before it - 64% of the pass - because the
beam-stop projection decodes on the GPU and never materialises the frame
on the host. Cutting frames is the only lever short of harvesting the
width from the two-pass run's first GPU pass.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CHMmeM1d489zvNFT7ZMN2P
leonarski_fandClaude Opus 5
1bb4cecbd1
