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Add Fejér-1 sampling and high-bandlimit Clenshaw–Curtis transforms - #428

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mwyau:enh/compact-cc-f1-analysis
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mwyau wants to merge 1 commit into
astro-informatics:mainfrom
mwyau:enh/compact-cc-f1-analysis

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@mwyau

@mwyau mwyau commented Oct 24, 2026 •

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Summary

Add Fejér's first-rule (f1) sampling and high-bandlimit Clenshaw–Curtis (cc) analysis, following Appendix A of Reinecke, Belkner & Carron (2023).

  • Add F1 sampling (L × 2L) and FFT-based quadrature weights following Waldvogel (2006).
  • Support high-bandlimit analysis through meridional Fourier extension and interpolation, requiring ntheta >= L+1 for CC and ntheta >= L for F1.
  • Infer latitude dimensions during forward analysis and add optional ntheta for inverse synthesis. Existing grid defaults remain unchanged.
  • Support NumPy/JAX scalar and spin-weighted transforms.

Testing

  • Local full test suite: 5,526 passed, 1,539 skipped (Python 3.13).
  • Reduced-grid CC/F1 tests, including L=72 comparisons against DUCC, nonzero-spin transforms, precomputations, JAX differentiation, and iterative refinement.
  • Pre-commit checks passed.

Related

@mwyau
mwyau force-pushed the enh/compact-cc-f1-analysis branch from 1730649 to 165cd30 Compare October 24, 2026 23:51
@mwyau
mwyau force-pushed the enh/compact-cc-f1-analysis branch from 165cd30 to 7ee17f9 Compare October 24, 2026 23:54
@mwyau
mwyau marked this pull request as ready for review October 25, 2026 01:33

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