From f41b1f1666e91dc674a42fed9c444c91f483133f Mon Sep 17 00:00:00 2001
From: Benoit Steiner <benoit.steiner.goog@gmail.com>
Date: Thu, 26 Feb 2015 09:42:41 -0800
Subject: Added support for fast reciprocal square root computation.

---
 Eigen/src/Core/functors/UnaryFunctors.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'Eigen/src/Core/functors')

diff --git a/Eigen/src/Core/functors/UnaryFunctors.h b/Eigen/src/Core/functors/UnaryFunctors.h
index ec42e6850..a3b5f50b1 100644
--- a/Eigen/src/Core/functors/UnaryFunctors.h
+++ b/Eigen/src/Core/functors/UnaryFunctors.h
@@ -224,6 +224,25 @@ struct functor_traits<scalar_sqrt_op<Scalar> >
   };
 };
 
+/** \internal
+  * \brief Template functor to compute the reciprocal square root of a scalar
+  * \sa class CwiseUnaryOp, Cwise::rsqrt()
+  */
+template<typename Scalar> struct scalar_rsqrt_op {
+  EIGEN_EMPTY_STRUCT_CTOR(scalar_rsqrt_op)
+  EIGEN_DEVICE_FUNC inline const Scalar operator() (const Scalar& a) const { using std::sqrt; return Scalar(1)/sqrt(a); }
+  typedef typename packet_traits<Scalar>::type Packet;
+  inline Packet packetOp(const Packet& a) const { return internal::prsqrt(a); }
+};
+
+template<typename Scalar>
+struct functor_traits<scalar_rsqrt_op<Scalar> >
+{ enum {
+    Cost = 5 * NumTraits<Scalar>::MulCost,
+    PacketAccess = packet_traits<Scalar>::HasRsqrt
+  };
+};
+
 /** \internal
   * \brief Template functor to compute the cosine of a scalar
   * \sa class CwiseUnaryOp, ArrayBase::cos()
-- 
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