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Avoid producing erf(x) = NaN for large |x|.

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This commit is contained in:
Rasmus Munk Larsen 2024-10-04 12:15:23 -07:00
parent 44b16f48cb
commit a097f728fe
1 changed files with 4 additions and 2 deletions
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6
unsupported/Eigen/src/SpecialFunctions/SpecialFunctionsImpl.h
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@ -298,7 +298,9 @@ EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T generic_fast_erf_float(const T& x) {
const T beta_10 = pset1<T>(3.89185734093189239501953125000e-05f);
// Since the polynomials are odd/even, we need x^2.
const T x2 = pmul(x, x);
// Since erf(4) == 1 in float, we clamp x^2 to 16 to avoid
// computing Inf/Inf below.
const T x2 = pmin(pset1<T>(16.0f), pmul(x, x));
// Evaluate the numerator polynomial p.
T p = pmadd(x2, alpha_11, alpha_9);
@ -307,13 +309,13 @@ EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T generic_fast_erf_float(const T& x) {
p = pmadd(x2, p, alpha_3);
p = pmadd(x2, p, alpha_1);
p = pmul(x, p);
// Evaluate the denominator polynomial p.
T q = pmadd(x2, beta_10, beta_8);
q = pmadd(x2, q, beta_6);
q = pmadd(x2, q, beta_4);
q = pmadd(x2, q, beta_2);
q = pmadd(x2, q, beta_0);
const T r = pdiv(p, q);
// Clamp to [-1:1].