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Keep von Mises pdf stable after norm_const access#3225

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FlorianPfaff merged 3 commits into
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fix-von-mises-stable-pdf-cache
Jun 27, 2026
Merged

Keep von Mises pdf stable after norm_const access#3225
FlorianPfaff merged 3 commits into
mainfrom
fix-von-mises-stable-pdf-cache

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@FlorianPfaff

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Summary

  • keep automatically computed von Mises normalizers from changing pdf() to the unstable unscaled evaluation path
  • preserve explicit norm_const behavior for callers that provide one
  • add a regression test for large-concentration PDF evaluation after norm_const has been accessed

Bug fixed

For large concentrations, norm_const can overflow because it uses the unscaled Bessel function iv(0, kappa). Accessing dist.norm_const therefore cached inf; later dist.pdf() switched to exp(kappa * cos(...)) / norm_const, which evaluates to inf / inf at the mode and returns nan. The default pdf() path is already stable via ive, so the fix keeps auto-computed normalizers on that scaled path.

Validation

  • python -m py_compile src/pyrecest/distributions/circle/von_mises_distribution.py tests/distributions/test_von_mises_distribution.py on the patched files
  • Reproduced the numerical failure locally with SciPy/NumPy formulas (kappa=1000, mode point): unscaled path produced nan, scaled path stayed finite
  • Full repository test suite was not run because the execution sandbox cannot resolve github.com to clone/install the repository

@FlorianPfaff FlorianPfaff enabled auto-merge (squash) June 27, 2026 10:04
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✅ JSON prettier 7 0 0 0 1.03s
✅ JSON v8r 7 0 0 5.3s
✅ MARKDOWN markdownlint 68 0 0 0 1.93s
✅ MARKDOWN markdown-table-formatter 68 0 0 0 0.62s
✅ PYTHON black 1044 48 0 0 66.88s
✅ PYTHON isort 1044 69 0 0 5.55s
✅ REPOSITORY checkov yes no no 51.12s
✅ REPOSITORY gitleaks yes no no 7.39s
✅ REPOSITORY git_diff yes no no 0.2s
✅ REPOSITORY secretlint yes no no 34.21s
✅ REPOSITORY syft yes no no 4.1s
✅ REPOSITORY trivy-sbom yes no no 11.23s
✅ REPOSITORY trufflehog yes no no 21.47s
✅ YAML prettier 11 0 0 0 0.77s
✅ YAML v8r 11 0 0 12.7s
✅ YAML yamllint 11 0 0 0.57s

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@FlorianPfaff FlorianPfaff merged commit fae8dbb into main Jun 27, 2026
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