Each crystal's (psi_x, psi_y) tilt was refined by a Ceres problem rebuilt for every inner
iteration: one auto-differentiated residual block and one Cauchy loss per reflection. With the
scaling reference cleaned up it was 70% of the stills scale/merge. The same objective - Cauchy
on the sigma-weighted intensity residuals plus the Gaussian prior on the tilt, the tilt bounded -
is now minimised by a small Levenberg-Marquardt on the rho'-reweighted 2x2 normal equations,
the tilt applied to all reflections through one rotation matrix and the Jacobian taken by
central differences.
It reaches the same answer to optimizer precision: on the new synthetic test
(StillsPartialityRefine_RecoversTheTilt) partiality error 0.0559 -> 0.03019 with Ceres and
0.03016 with this, mean tilt 0.02065 vs 0.02067 deg; on two 25k-frame XFEL runs (--mode scale)
CC1/2, I/sigma, R_pim and the CC against a deposited lysozyme model agree to 0.0005, mean
|dpsi| 0.023 deg on both. Scale+merge 6.9 -> 3.0 s (--mode scale, loaded box).
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 5.5
3c4d730f89