[us-commits] [ehb54/ultrascan3] 17b638: Guard recompute_errors mode 'I' against negative/z...

[emre brookes]

  Branch: refs/heads/ehb54-issue-966
  Home:   https://github.com/ehb54/ultrascan3
  Commit: 17b63846933b108cf79aa0781ecab9fe533859f5
      https://github.com/ehb54/ultrascan3/commit/17b63846933b108cf79aa0781ecab9fe533859f5
  Author: ehb54 <brookes at uthscsa.edu>
  Date:   2026-07-13 (Mon, 13 Jul 2026)

  Changed paths:
    M us_somo/develop/include/us_saxs_util.h
    M us_somo/develop/src/us_saxs_util_static.cpp

  Log Message:
  -----------
  Guard recompute_errors mode 'I' against negative/zero-crossing intensities

On background-subtracted or extrapolated curves I(q) crosses zero, and the
signed intensity term sigma+a*I could go negative, blowing up the a search
and emitting negative sigma (observed factors -13..1087 on real data). Use
sigma+a*|I| so the term is always >= sigma > 0. Add a general safety clamp
so no mode ever writes a non-positive or non-finite sigma (degenerate factor
falls back to 1). Modes C and N are unchanged.

Implements ehb54/ultrascan-tickets#966

Co-Authored-By: Claude Fable 5 <noreply at anthropic.com>



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