From 4213b63f5ce33d3f904674ee7b0cabd6934dda6b Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Wed, 4 Apr 2018 15:12:43 +0200
Subject: Factories code between numext::hypot and scalar_hyot_op functor.

---
 Eigen/src/Core/MathFunctionsImpl.h       | 20 ++++++++++++--------
 Eigen/src/Core/functors/BinaryFunctors.h | 25 +++++++++----------------
 2 files changed, 21 insertions(+), 24 deletions(-)

(limited to 'Eigen')

diff --git a/Eigen/src/Core/MathFunctionsImpl.h b/Eigen/src/Core/MathFunctionsImpl.h
index 034cfad7b..cc2ac0700 100644
--- a/Eigen/src/Core/MathFunctionsImpl.h
+++ b/Eigen/src/Core/MathFunctionsImpl.h
@@ -66,6 +66,17 @@ T generic_fast_tanh_float(const T& a_x)
   return pdiv(p, q);
 }
 
+template<typename RealScalar>
+EIGEN_STRONG_INLINE
+RealScalar positive_real_hypot(const RealScalar& x, const RealScalar& y)
+{
+  EIGEN_USING_STD_MATH(sqrt);
+  RealScalar p, qp;
+  p = numext::maxi(x,y);
+  if(p==RealScalar(0)) return RealScalar(0);
+  qp = numext::mini(y,x) / p;    
+  return p * sqrt(RealScalar(1) + qp*qp);
+}
 
 template<typename Scalar>
 struct hypot_impl
@@ -74,14 +85,7 @@ struct hypot_impl
   static inline RealScalar run(const Scalar& x, const Scalar& y)
   {
     EIGEN_USING_STD_MATH(abs);
-    EIGEN_USING_STD_MATH(sqrt);
-    RealScalar _x = abs(x);
-    RealScalar _y = abs(y);
-    RealScalar p, qp;
-    p = numext::maxi(_x,_y);
-    if(p==RealScalar(0)) return RealScalar(0);
-    qp = numext::mini(_y,_x) / p;    
-    return p * sqrt(RealScalar(1) + qp*qp);
+    return positive_real_hypot(abs(x), abs(y));
   }
 };
 
diff --git a/Eigen/src/Core/functors/BinaryFunctors.h b/Eigen/src/Core/functors/BinaryFunctors.h
index 96747bac7..3eae6b8ca 100644
--- a/Eigen/src/Core/functors/BinaryFunctors.h
+++ b/Eigen/src/Core/functors/BinaryFunctors.h
@@ -255,7 +255,7 @@ struct scalar_cmp_op<LhsScalar,RhsScalar, cmp_NEQ> : binary_op_base<LhsScalar,Rh
 
 
 /** \internal
-  * \brief Template functor to compute the hypot of two scalars
+  * \brief Template functor to compute the hypot of two \b positive \b and \b real scalars
   *
   * \sa MatrixBase::stableNorm(), class Redux
   */
@@ -263,22 +263,15 @@ template<typename Scalar>
 struct scalar_hypot_op<Scalar,Scalar> : binary_op_base<Scalar,Scalar>
 {
   EIGEN_EMPTY_STRUCT_CTOR(scalar_hypot_op)
-//   typedef typename NumTraits<Scalar>::Real result_type;
-  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Scalar operator() (const Scalar& _x, const Scalar& _y) const
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Scalar operator() (const Scalar &x, const Scalar &y) const
   {
-    EIGEN_USING_STD_MATH(sqrt)
-    Scalar p, qp;
-    if(_x>_y)
-    {
-      p = _x;
-      qp = _y / p;
-    }
-    else
-    {
-      p = _y;
-      qp = _x / p;
-    }
-    return p * sqrt(Scalar(1) + qp*qp);
+    // This functor is used by hypotNorm only for which it is faster to first apply abs
+    // on all coefficients prior to reduction through hypot.
+    // This way we avoid calling abs on positive and real entries, and this also permits
+    // to seamlessly handle complexes. Otherwise we would have to handle both real and complexes
+    // through the same functor...
+    return internal::positive_real_hypot(x,y);
   }
 };
 template<typename Scalar>
-- 
cgit v1.2.3