From a0e8577b49693df630b9b35b0fee2c89a9ec12ad Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Fri, 18 Oct 2013 14:56:36 +0200
Subject: Fix bug #684: optimize vectorization of array-scalar and scalar-array

---
 Eigen/src/Core/Functors.h               | 41 +++++++++++++++++++++++++++++++--
 Eigen/src/plugins/ArrayCwiseBinaryOps.h |  8 +++----
 2 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/Eigen/src/Core/Functors.h b/Eigen/src/Core/Functors.h
index 69d95ea30..d0e05fcf2 100644
--- a/Eigen/src/Core/Functors.h
+++ b/Eigen/src/Core/Functors.h
@@ -22,6 +22,7 @@ namespace internal {
   * \sa class CwiseBinaryOp, MatrixBase::operator+, class VectorwiseOp, DenseBase::sum()
   */
 template<typename Scalar> struct scalar_sum_op {
+//   typedef Scalar result_type;
   EIGEN_EMPTY_STRUCT_CTOR(scalar_sum_op)
   EIGEN_STRONG_INLINE const Scalar operator() (const Scalar& a, const Scalar& b) const { return a + b; }
   template<typename Packet>
@@ -45,8 +46,8 @@ struct functor_traits<scalar_sum_op<Scalar> > {
   * \sa DenseBase::count(), DenseBase::any(), ArrayBase::cast(), MatrixBase::cast()
   */
 template<> struct scalar_sum_op<bool> : scalar_sum_op<int> {
-	EIGEN_DEPRECATED
-	scalar_sum_op() {}
+  EIGEN_DEPRECATED
+  scalar_sum_op() {}
 };
 
 
@@ -689,6 +690,42 @@ template<typename Scalar>
 struct functor_traits<scalar_add_op<Scalar> >
 { enum { Cost = NumTraits<Scalar>::AddCost, PacketAccess = packet_traits<Scalar>::HasAdd }; };
 
+/** \internal
+  * \brief Template functor to subtract a fixed scalar to another one
+  * \sa class CwiseUnaryOp, Array::operator-, struct scalar_add_op, struct scalar_rsub_op
+  */
+template<typename Scalar>
+struct scalar_sub_op {
+  typedef typename packet_traits<Scalar>::type Packet;
+  inline scalar_sub_op(const scalar_sub_op& other) : m_other(other.m_other) { }
+  inline scalar_sub_op(const Scalar& other) : m_other(other) { }
+  inline Scalar operator() (const Scalar& a) const { return a - m_other; }
+  inline const Packet packetOp(const Packet& a) const
+  { return internal::psub(a, pset1<Packet>(m_other)); }
+  const Scalar m_other;
+};
+template<typename Scalar>
+struct functor_traits<scalar_sub_op<Scalar> >
+{ enum { Cost = NumTraits<Scalar>::AddCost, PacketAccess = packet_traits<Scalar>::HasAdd }; };
+
+/** \internal
+  * \brief Template functor to subtract a scalar to fixed another one
+  * \sa class CwiseUnaryOp, Array::operator-, struct scalar_add_op, struct scalar_sub_op
+  */
+template<typename Scalar>
+struct scalar_rsub_op {
+  typedef typename packet_traits<Scalar>::type Packet;
+  inline scalar_rsub_op(const scalar_rsub_op& other) : m_other(other.m_other) { }
+  inline scalar_rsub_op(const Scalar& other) : m_other(other) { }
+  inline Scalar operator() (const Scalar& a) const { return m_other - a; }
+  inline const Packet packetOp(const Packet& a) const
+  { return internal::psub(pset1<Packet>(m_other), a); }
+  const Scalar m_other;
+};
+template<typename Scalar>
+struct functor_traits<scalar_rsub_op<Scalar> >
+{ enum { Cost = NumTraits<Scalar>::AddCost, PacketAccess = packet_traits<Scalar>::HasAdd }; };
+
 /** \internal
   * \brief Template functor to compute the square root of a scalar
   * \sa class CwiseUnaryOp, Cwise::sqrt()
diff --git a/Eigen/src/plugins/ArrayCwiseBinaryOps.h b/Eigen/src/plugins/ArrayCwiseBinaryOps.h
index 5c8c476ee..65d198749 100644
--- a/Eigen/src/plugins/ArrayCwiseBinaryOps.h
+++ b/Eigen/src/plugins/ArrayCwiseBinaryOps.h
@@ -162,16 +162,16 @@ operator+(const Scalar& scalar,const EIGEN_CURRENT_STORAGE_BASE_CLASS<Derived>&
   *
   * \sa operator+(), operator-=()
   */
-inline const CwiseUnaryOp<internal::scalar_add_op<Scalar>, const Derived>
+inline const CwiseUnaryOp<internal::scalar_sub_op<Scalar>, const Derived>
 operator-(const Scalar& scalar) const
 {
-  return *this + (-scalar);
+  return CwiseUnaryOp<internal::scalar_sub_op<Scalar>, const Derived>(derived(), internal::scalar_sub_op<Scalar>(scalar));;
 }
 
-friend inline const CwiseUnaryOp<internal::scalar_add_op<Scalar>, const CwiseUnaryOp<internal::scalar_opposite_op<Scalar>, const Derived> >
+friend inline const CwiseUnaryOp<internal::scalar_rsub_op<Scalar>, const Derived>
 operator-(const Scalar& scalar,const EIGEN_CURRENT_STORAGE_BASE_CLASS<Derived>& other)
 {
-  return (-other) + scalar;
+  return CwiseUnaryOp<internal::scalar_rsub_op<Scalar>, const Derived>(other.derived(), internal::scalar_rsub_op<Scalar>(scalar));;
 }
 
 /** \returns an expression of the coefficient-wise && operator of *this and \a other
-- 
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