The floor below which a frame's partial scale is not credible (MIN_CREDIBLE_SCALE_RATIO = 0.02) was
read off the MEDIAN fitted scale - in the loop's smoothing window, in its step, and in the guard
after it (DropCollapsedScales). On a sweep that spent most of its turn out of the beam the median is
itself a dead frame, and it walks: an empty frame's scale has no fixed point above zero, so the dead
frames slide toward zero round after round, the median and the floor slide with them, and frames on
the floor cross it, re-enter the window at their neighbours' scale (3x up in one round) and cross it
again. The loop then has no fixed point, and which frames reach the merge depends on the round it
stops on.
The floor is now read off the run's typical frame (TypicalFrameScale), which is what the loop pins
its gauge to - inside the loop it is the constant 0.02, so it stands still. The fulls' guard keeps
the median (their scales are not gauge-pinned). Dropped frames still carry the median scale, so the
sweep ledger reads them as before.
lyso_x06da_half_image (1800 frames, two thirds weak or out of the beam; median frame at 1/5.7 of the
typical one): traced, the final loop's floor fell 2.4x and every spike in its step was one frame
re-entering the window; the R_meas 287% -> 685% of the rc178 loop fixes was the same non-settling
loop ended by two stopping rules (delta-CC1/2 split the weak stretch differently, 206 frames at
1/20-1/50 of the median merged or not). The pre-pass P1 loop that crept to the cap is the geometry
pre-pass, which commits nothing here.
battery --only, before (rc178-aa-tol5 f217f180a) -> after, GPU:
- lyso_x06da_half_image: R_meas 689% -> 81%, CC1/2 0.932 -> 0.971, REFRES CC1/2 0.484 -> 0.911,
ISa 4.13 -> 4.22, model R-free 0.3302 -> 0.3271, CC_model 0.826 -> 0.829; final loop's smallest
step 5.6e-3 -> 1.8e-4. --no-gpu gives the same numbers.
- lcystine_x10sa_25keV: R_meas 0.396 -> 0.202, ISa 4.45 -> 8.49, CC1/2 0.9987 -> 0.9998.
- lyso_x10sa_strong: R_meas 0.238 -> 0.151, ISa 5.51 -> 5.74, R-free 0.3653 -> 0.3658,
CC_model 0.859 -> 0.857, d_min 1.354 -> 1.344.
- insu_I_x06da_ref: R_meas 0.347 -> 0.290, R-free and ISa unchanged.
- 7mzt: CC1/2 0.967 -> 0.983, CC_model 0.532 -> 0.548, R-free 0.4183 -> 0.4197, d_min 3.18 -> 3.21.
- unchanged: lyso_x06da_ref, myob_x06da_split, myob_x06da_powder_2, thau_bl1a_4p6keV, 6o2h,
3meb, 9z72, 9o0h. Space groups identical on all 13.
Tests: [RotationScale], AndersonMixing* pass.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PXc1zD1yxHqaR1DGdCTHL4
leonarski_fandClaude Opus 5.5
2a5d303886