diff options
author | Benoit Steiner <benoit.steiner.goog@gmail.com> | 2015-03-02 09:38:47 -0800 |
---|---|---|
committer | Benoit Steiner <benoit.steiner.goog@gmail.com> | 2015-03-02 09:38:47 -0800 |
commit | 4fd7f47692ca689559999f05def578bfe4e9f545 (patch) | |
tree | fabc697b9acaa95bb263bb031d3434ad31c32f62 /Eigen/src/Core/arch/SSE/MathFunctions.h | |
parent | ae73859a0aabb389be20df4106fd541c7942bcde (diff) |
Added an optimized version of rsqrt for SSE and AVX that is used when EIGEN_FAST_MATH is defined.
Diffstat (limited to 'Eigen/src/Core/arch/SSE/MathFunctions.h')
-rw-r--r-- | Eigen/src/Core/arch/SSE/MathFunctions.h | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/Eigen/src/Core/arch/SSE/MathFunctions.h b/Eigen/src/Core/arch/SSE/MathFunctions.h index f9cb93bfc..3b8b7303f 100644 --- a/Eigen/src/Core/arch/SSE/MathFunctions.h +++ b/Eigen/src/Core/arch/SSE/MathFunctions.h @@ -470,12 +470,46 @@ Packet4f psqrt<Packet4f>(const Packet4f& x) { return _mm_sqrt_ps(x); } template<> EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS EIGEN_UNUSED Packet2d psqrt<Packet2d>(const Packet2d& x) { return _mm_sqrt_pd(x); } +#if EIGEN_FAST_MATH + +template<> EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS EIGEN_UNUSED +Packet4f prsqrt<Packet4f>(const Packet4f& _x) { + _EIGEN_DECLARE_CONST_Packet4f_FROM_INT(inf, 0x7f800000); + _EIGEN_DECLARE_CONST_Packet4f_FROM_INT(nan, 0x7fc00000); + _EIGEN_DECLARE_CONST_Packet4f(one_point_five, 1.5f); + _EIGEN_DECLARE_CONST_Packet4f(minus_half, -0.5f); + _EIGEN_DECLARE_CONST_Packet4f_FROM_INT(flt_min, 0x00800000); + + Packet4f neg_half = pmul(_x, p4f_minus_half); + + // select only the inverse sqrt of positive normal inputs (denormals are + // flushed to zero and cause infs as well). + Packet4f le_zero_mask = _mm_cmple_ps(_x, p4f_flt_min); + Packet4f x = _mm_andnot_ps(le_zero_mask, _mm_rsqrt_ps(_x)); + + // Fill in NaNs and Infs for the negative/zero entries. + Packet4f neg_mask = _mm_cmplt_ps(_x, _mm_setzero_ps()); + Packet4f zero_mask = _mm_andnot_ps(neg_mask, le_zero_mask); + Packet4f infs_and_nans = _mm_or_ps(_mm_and_ps(neg_mask, p4f_nan), + _mm_and_ps(zero_mask, p4f_inf)); + + // Do a single step of Newton's iteration. + x = pmul(x, pmadd(neg_half, pmul(x, x), p4f_one_point_five)); + + // Insert NaNs and Infs in all the right places. + return _mm_or_ps(x, infs_and_nans); +} + +#else + template<> EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS EIGEN_UNUSED Packet4f prsqrt<Packet4f>(const Packet4f& x) { // Unfortunately we can't use the much faster mm_rqsrt_ps since it only provides an approximation. return _mm_div_ps(pset1<Packet4f>(1.0f), _mm_sqrt_ps(x)); } +#endif + template<> EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS EIGEN_UNUSED Packet2d prsqrt<Packet2d>(const Packet2d& x) { // Unfortunately we can't use the much faster mm_rqsrt_pd since it only provides an approximation. |