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Factorize the 4 copies of tanh implementations, make numext::tanh consistent with array::tanh, enable fast tanh in fast-math mode only.

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This commit is contained in:
Gael Guennebaud
2016-08-23 14:23:08 +02:00
parent 82147cefff
commit a4c266f827
6 changed files with 89 additions and 193 deletions
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46
Eigen/src/Core/arch/SSE/MathFunctions.h
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@@ -517,52 +517,10 @@ Packet2d prsqrt<Packet2d>(const Packet2d& x) {
}
// Hyperbolic Tangent function.
// Doesn't do anything fancy, just a 13/6-degree rational interpolant which
// is accurate up to a couple of ulp in the range [-9, 9], outside of which the
// fl(tanh(x)) = +/-1.
template <>
EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS EIGEN_UNUSED Packet4f
ptanh<Packet4f>(const Packet4f& _x) {
// Clamp the inputs to the range [-9, 9] since anything outside
// this range is +/-1.0f in single-precision.
_EIGEN_DECLARE_CONST_Packet4f(plus_9, 9.0f);
_EIGEN_DECLARE_CONST_Packet4f(minus_9, -9.0f);
const Packet4f x = pmax(p4f_minus_9, pmin(p4f_plus_9, _x));
// The monomial coefficients of the numerator polynomial (odd).
_EIGEN_DECLARE_CONST_Packet4f(alpha_1, 4.89352455891786e-03f);
_EIGEN_DECLARE_CONST_Packet4f(alpha_3, 6.37261928875436e-04f);
_EIGEN_DECLARE_CONST_Packet4f(alpha_5, 1.48572235717979e-05f);
_EIGEN_DECLARE_CONST_Packet4f(alpha_7, 5.12229709037114e-08f);
_EIGEN_DECLARE_CONST_Packet4f(alpha_9, -8.60467152213735e-11f);
_EIGEN_DECLARE_CONST_Packet4f(alpha_11, 2.00018790482477e-13f);
_EIGEN_DECLARE_CONST_Packet4f(alpha_13, -2.76076847742355e-16f);
// The monomial coefficients of the denominator polynomial (even).
_EIGEN_DECLARE_CONST_Packet4f(beta_0, 4.89352518554385e-03f);
_EIGEN_DECLARE_CONST_Packet4f(beta_2, 2.26843463243900e-03f);
_EIGEN_DECLARE_CONST_Packet4f(beta_4, 1.18534705686654e-04f);
_EIGEN_DECLARE_CONST_Packet4f(beta_6, 1.19825839466702e-06f);
// Since the polynomials are odd/even, we need x^2.
const Packet4f x2 = pmul(x, x);
// Evaluate the numerator polynomial p.
Packet4f p = pmadd(x2, p4f_alpha_13, p4f_alpha_11);
p = pmadd(x2, p, p4f_alpha_9);
p = pmadd(x2, p, p4f_alpha_7);
p = pmadd(x2, p, p4f_alpha_5);
p = pmadd(x2, p, p4f_alpha_3);
p = pmadd(x2, p, p4f_alpha_1);
p = pmul(x, p);
// Evaluate the denominator polynomial p.
Packet4f q = pmadd(x2, p4f_beta_6, p4f_beta_4);
q = pmadd(x2, q, p4f_beta_2);
q = pmadd(x2, q, p4f_beta_0);
// Divide the numerator by the denominator.
return pdiv(p, q);
ptanh<Packet4f>(const Packet4f& x) {
return internal::generic_fast_tanh_float(x);
}
} // end namespace internal