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Update comment for fast sqrt.

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This commit is contained in:
Rasmus Munk Larsen 2016-10-04 15:09:11 -07:00
parent 765615609d
commit 7f67e6dfdb
1 changed files with 5 additions and 3 deletions
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8
Eigen/src/Core/arch/AVX/MathFunctions.h
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@ -355,9 +355,11 @@ pexp<Packet4d>(const Packet4d& _x) {
// Functions for sqrt.
// The EIGEN_FAST_MATH version uses the _mm_rsqrt_ps approximation and one step
// of Newton's method, at a cost of 1-2 bits of precision as opposed to the
// exact solution. The main advantage of this approach is not just speed, but
// also the fact that it can be inlined and pipelined with other computations,
// further reducing its effective latency.
// exact solution. It does not handle +inf, or denormalized numbers correctly.
// The main advantage of this approach is not just speed, but also the fact that
// it can be inlined and pipelined with other computations, further reducing its
// effective latency. This is similar to Quake3's fast inverse square root.
// For detail see here: http://www.beyond3d.com/content/articles/8/
#if EIGEN_FAST_MATH
template <>
EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS EIGEN_UNUSED Packet8f