Degree-13 odd-polynomial coefficients: erf(x) ≈ x·Σ cₖ·x^(2k) on
[0, 3], constrained least-squares (equality constraint P(3) = 1),
fitted against the exact erf on a 6000-point grid. The tail
coefficients are the toFixed(9) roundings of the fit; c₀ is then
RE-SOLVED against the rounded tail so the printed set itself satisfies
P(3) = 1 to 1e-9 (plain rounding of all seven broke the constraint by
9.5e-5). These printed values are what both shader backends and
erfPoly evaluate; the f64 mirror matches a float32-chained
evaluation to within ~7e-6 (accumulated rounding across the Horner
steps — 1% of the fit error). Max abs error vs the exact erf: 5.4e-4.
Degree-13 odd-polynomial coefficients: erf(x) ≈ x·Σ cₖ·x^(2k) on [0, 3], constrained least-squares (equality constraint P(3) = 1), fitted against the exact erf on a 6000-point grid. The tail coefficients are the
toFixed(9)roundings of the fit; c₀ is then RE-SOLVED against the rounded tail so the printed set itself satisfies P(3) = 1 to 1e-9 (plain rounding of all seven broke the constraint by 9.5e-5). These printed values are what both shader backends anderfPolyevaluate; the f64 mirror matches a float32-chained evaluation to within ~7e-6 (accumulated rounding across the Horner steps — 1% of the fit error). Max abs error vs the exact erf: 5.4e-4.