The partials and fulls scaling loops are alternating least squares that converge linearly:
over the rc176 battery's 2527 loops a round shrinks the step by a median 0.86 (partials) and
0.93 (fulls), up to 0.98, so the 1e-3 step tolerance stopped them 0.6% / 1.4% (median) and up to
17% (fulls p90) short of their fixed point, and 313 of them were stopped as "stalled" when they
were only slow - a stalled fulls loop also skipped ShrinkToRestrained.
Each round is now accelerated in log G by type-II Anderson mixing (Walker & Ni 2011), depth 5,
each frame weighted by its observation count as in the step test; frames below the credible floor
take the plain round's scale. The history is dropped when the weighted residual grows or the set
of fitted frames changes (new AndersonMixing class, unit-tested on a synthetic slow ALS loop). The
mixed scales are gauge-pinned again before the rescale, and the stop test is unchanged: it reads
the round's residual F(x) - x, so "stalled" now means a loop that does not settle under
acceleration either.
Measured (CPU, -N 8): 4nwv 311 -> 82 iterations over 9 loops, 9v16 76 iterations over 11 loops,
the same counts as the env-gated prototype on tail-solver; no history restart fired on either.
Depth 3/5/8 give 92/91/90 iterations on 4nwv. A restart on a change of the fulls loop's
cross-validated lambda was tried and gave nothing (83 vs 82). Same space group and merging
statistics on 4nwv and 9v16.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PXc1zD1yxHqaR1DGdCTHL4
