add fixed power unary operation

2025-08-11 03:09:01 +08:00 · 2022-08-16 21:32:36 +00:00 · 2022-08-16 21:32:36 +00:00 · 76a669fb45
commit 76a669fb45
parent 39fcc89798
9 changed files with 391 additions and 39 deletions
--- a/Eigen/src/Core/GlobalFunctions.h
+++ b/Eigen/src/Core/GlobalFunctions.h
@ -109,23 +109,25 @@ namespace Eigen
    *
    * \relates ArrayBase
    */
+    
+template <typename Derived, typename ScalarExponent>
+using GlobalUnaryPowReturnType = std::enable_if_t<
+    !internal::is_arithmetic<Derived>::value && internal::is_arithmetic<ScalarExponent>::value,
+    CwiseUnaryOp<internal::scalar_unary_pow_op<typename Derived::Scalar, ScalarExponent>, const Derived> >;
+
 #ifdef EIGEN_PARSED_BY_DOXYGEN
-  template<typename Derived,typename ScalarExponent>
-  inline const CwiseBinaryOp<internal::scalar_pow_op<Derived::Scalar,ScalarExponent>,Derived,Constant<ScalarExponent> >
-  pow(const Eigen::ArrayBase<Derived>& x, const ScalarExponent& exponent);
+template <typename Derived, typename ScalarExponent>
+EIGEN_DEVICE_FUNC inline const GlobalUnaryPowReturnType<Derived, ScalarExponent>
+pow(const Eigen::ArrayBase<Derived>& x, const ScalarExponent& exponent);
 #else
-  template <typename Derived,typename ScalarExponent>
-  EIGEN_DEVICE_FUNC inline
-    const EIGEN_EXPR_BINARYOP_SCALAR_RETURN_TYPE(Derived,typename internal::promote_scalar_arg<typename Derived::Scalar
-                                                 EIGEN_COMMA ScalarExponent EIGEN_COMMA
-                                                 EIGEN_SCALAR_BINARY_SUPPORTED(pow,typename Derived::Scalar,ScalarExponent)>::type,pow)
-  pow(const Eigen::ArrayBase<Derived>& x, const ScalarExponent& exponent)
-  {
-    typedef typename internal::promote_scalar_arg<typename Derived::Scalar,ScalarExponent,
-                                                  EIGEN_SCALAR_BINARY_SUPPORTED(pow,typename Derived::Scalar,ScalarExponent)>::type PromotedExponent;
-    return EIGEN_EXPR_BINARYOP_SCALAR_RETURN_TYPE(Derived,PromotedExponent,pow)(x.derived(),
-           typename internal::plain_constant_type<Derived,PromotedExponent>::type(x.derived().rows(), x.derived().cols(), internal::scalar_constant_op<PromotedExponent>(exponent)));
-  }
+template <typename Derived, typename ScalarExponent>
+EIGEN_DEVICE_FUNC inline const typename std::enable_if<
+    !internal::is_arithmetic<Derived>::value && internal::is_arithmetic<ScalarExponent>::value,
+    CwiseUnaryOp<internal::scalar_unary_pow_op<typename Derived::Scalar, ScalarExponent>, const Derived> >::type
+pow(const Eigen::ArrayBase<Derived>& x, const ScalarExponent& exponent) {
+  return CwiseUnaryOp<internal::scalar_unary_pow_op<typename Derived::Scalar, ScalarExponent>, const Derived>(
+      x.derived(), internal::scalar_unary_pow_op<typename Derived::Scalar, ScalarExponent>(exponent));
+}
 #endif

  /** \returns an expression of the coefficient-wise power of \a x to the given array of \a exponents.
--- a/Eigen/src/Core/arch/Default/GenericPacketMathFunctions.h
+++ b/Eigen/src/Core/arch/Default/GenericPacketMathFunctions.h
@ -1690,6 +1690,225 @@ struct pchebevl {
  }
 };

+namespace unary_pow {
+template <typename ScalarExponent, bool IsIntegerAtCompileTime = NumTraits<ScalarExponent>::IsInteger>
+struct is_odd {
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE ScalarExponent run(const ScalarExponent& x) {
+    ScalarExponent xdiv2 = x / ScalarExponent(2);
+    ScalarExponent floorxdiv2 = numext::floor(xdiv2);
+    return xdiv2 != floorxdiv2;
+  }
+};
+template <typename ScalarExponent>
+struct is_odd<ScalarExponent, true> {
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE ScalarExponent run(const ScalarExponent& x) {
+    return x % ScalarExponent(2);
+  }
+};
+
+template <typename Packet, typename ScalarExponent,
+          bool BaseIsIntegerType = NumTraits<typename unpacket_traits<Packet>::type>::IsInteger>
+struct do_div {
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet run(const Packet& x, const ScalarExponent& exponent) {
+    typedef typename unpacket_traits<Packet>::type Scalar;
+    const Packet cst_pos_one = pset1<Packet>(Scalar(1));
+    return exponent < 0 ? pdiv(cst_pos_one, x) : x;
+  }
+};
+
+template <typename Packet, typename ScalarExponent>
+struct do_div<Packet, ScalarExponent, true> {
+  // pdiv not defined, nor necessary for integer base types
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet run(const Packet& x, const ScalarExponent& exponent) {
+    EIGEN_UNUSED_VARIABLE(exponent);
+    return x;
+  }
+};
+
+template <typename Packet, typename ScalarExponent>
+static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet int_pow(const Packet& x, const ScalarExponent& exponent) {
+  typedef typename unpacket_traits<Packet>::type Scalar;
+  const Packet cst_pos_one = pset1<Packet>(Scalar(1));
+  if (exponent == 0) return cst_pos_one;
+  Packet result = x;
+  Packet y = cst_pos_one;
+  ScalarExponent m = numext::abs(exponent);
+  while (m > 1) {
+    bool odd = is_odd<ScalarExponent>::run(m);
+    if (odd) y = pmul(y, result);
+    result = pmul(result, result);
+    m = numext::floor(m / ScalarExponent(2));
+  }
+  result = pmul(y, result);
+  result = do_div<Packet, ScalarExponent>::run(result, exponent);
+  return result;
+}
+
+template <typename Packet>
+static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet gen_pow(const Packet& x,
+                                                            const typename unpacket_traits<Packet>::type& exponent) {
+  const Packet exponent_packet = pset1<Packet>(exponent);
+  return generic_pow_impl(x, exponent_packet);
+}
+
+template <typename Packet, typename ScalarExponent>
+static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet handle_nonint_int_errors(const Packet& x, const Packet& powx,
+                                                                             const ScalarExponent& exponent) {
+  typedef typename unpacket_traits<Packet>::type Scalar;
+
+  // non-integer base, integer exponent case
+
+  const bool exponent_is_odd = is_odd<ScalarExponent>::run(exponent);
+  const bool exponent_is_neg = exponent < 0;
+
+  const Packet exp_is_odd = exponent_is_odd ? ptrue(x) : pzero(x);
+  const Packet exp_is_neg = exponent_is_neg ? ptrue(x) : pzero(x);
+
+  const Scalar pos_zero = Scalar(0);
+  const Scalar neg_zero = -Scalar(0);
+  const Scalar pos_one = Scalar(1);
+  const Scalar pos_inf = NumTraits<Scalar>::infinity();
+  const Scalar neg_inf = -NumTraits<Scalar>::infinity();
+
+  const Packet cst_pos_zero = pset1<Packet>(pos_zero);
+  const Packet cst_neg_zero = pset1<Packet>(neg_zero);
+  const Packet cst_pos_one = pset1<Packet>(pos_one);
+  const Packet cst_pos_inf = pset1<Packet>(pos_inf);
+  const Packet cst_neg_inf = pset1<Packet>(neg_inf);
+
+  const Packet abs_x = pabs(x);
+  const Packet abs_x_is_zero = pcmp_eq(abs_x, cst_pos_zero);
+  const Packet abs_x_is_one = pcmp_eq(abs_x, cst_pos_one);
+  const Packet abs_x_is_inf = pcmp_eq(abs_x, cst_pos_inf);
+
+  const Packet x_has_signbit = pcmp_eq(por(pand(x, cst_neg_inf), cst_pos_inf), cst_neg_inf);
+  const Packet x_is_neg = pandnot(x_has_signbit, abs_x_is_zero);
+  const Packet x_is_neg_zero = pand(x_has_signbit, abs_x_is_zero);
+
+  if (exponent == 0) {
+    return cst_pos_one;
+  }
+
+  Packet pow_is_pos_inf = pand(pandnot(abs_x_is_zero, x_is_neg_zero), pand(exp_is_odd, exp_is_neg));
+  pow_is_pos_inf = por(pow_is_pos_inf, pand(abs_x_is_zero, pandnot(exp_is_neg, exp_is_odd)));
+  pow_is_pos_inf = por(pow_is_pos_inf, pand(pand(abs_x_is_inf, x_is_neg), pandnot(pnot(exp_is_neg), exp_is_odd)));
+  pow_is_pos_inf = por(pow_is_pos_inf, pandnot(pandnot(abs_x_is_inf, x_is_neg), exp_is_neg));
+
+  Packet pow_is_neg_inf = pand(x_is_neg_zero, pand(exp_is_neg, exp_is_odd));
+  pow_is_neg_inf = por(pow_is_neg_inf, pand(pand(abs_x_is_inf, x_is_neg), pandnot(exp_is_odd, exp_is_neg)));
+
+  Packet pow_is_pos_zero = pandnot(abs_x_is_zero, exp_is_neg);
+  pow_is_pos_zero = por(pow_is_pos_zero, pand(pand(abs_x_is_inf, x_is_neg), pandnot(exp_is_neg, exp_is_odd)));
+  pow_is_pos_zero = por(pow_is_pos_zero, pand(pandnot(abs_x_is_inf, x_is_neg), exp_is_neg));
+
+  Packet pow_is_neg_zero = pand(x_is_neg_zero, pandnot(exp_is_odd, exp_is_neg));
+  pow_is_neg_zero = por(pow_is_neg_zero, pand(pand(abs_x_is_inf, x_is_neg), pand(exp_is_odd, exp_is_neg)));
+
+  Packet result = pselect(pow_is_neg_inf, cst_neg_inf, powx);
+  result = pselect(pow_is_neg_zero, cst_neg_zero, result);
+  result = pselect(pow_is_pos_zero, cst_pos_zero, result);
+  result = pselect(pow_is_pos_inf, cst_pos_inf, result);
+  result = pselect(pandnot(abs_x_is_one, x_is_neg), cst_pos_one, result);
+  return result;
+}
+
+template <typename Packet, typename ScalarExponent>
+static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet handle_nonint_nonint_errors(const Packet& x, const Packet& powx,
+                                                                                const ScalarExponent& exponent) {
+  typedef typename unpacket_traits<Packet>::type Scalar;
+
+  // non-integer base and exponent case
+
+  const bool exponent_is_fin = (numext::isfinite)(exponent);
+  const bool exponent_is_nan = (numext::isnan)(exponent);
+  const bool exponent_is_neg = exponent < 0;
+  const bool exponent_is_inf = !exponent_is_fin && !exponent_is_nan;
+
+  const Packet exp_is_neg = exponent_is_neg ? ptrue(x) : pzero(x);
+  const Packet exp_is_inf = exponent_is_inf ? ptrue(x) : pzero(x);
+
+  const Scalar pos_zero = Scalar(0);
+  const Scalar pos_one = Scalar(1);
+  const Scalar pos_inf = NumTraits<Scalar>::infinity();
+  const Scalar neg_inf = -NumTraits<Scalar>::infinity();
+  const Scalar nan = NumTraits<Scalar>::quiet_NaN();
+
+  const Packet cst_pos_zero = pset1<Packet>(pos_zero);
+  const Packet cst_pos_one = pset1<Packet>(pos_one);
+  const Packet cst_pos_inf = pset1<Packet>(pos_inf);
+  const Packet cst_neg_inf = pset1<Packet>(neg_inf);
+  const Packet cst_nan = pset1<Packet>(nan);
+
+  const Packet abs_x = pabs(x);
+  const Packet abs_x_is_zero = pcmp_eq(abs_x, cst_pos_zero);
+  const Packet abs_x_is_lt_one = pcmp_lt(abs_x, cst_pos_one);
+  const Packet abs_x_is_gt_one = pcmp_lt(cst_pos_one, abs_x);
+  const Packet abs_x_is_one = pcmp_eq(abs_x, cst_pos_one);
+  const Packet abs_x_is_inf = pcmp_eq(abs_x, cst_pos_inf);
+
+  const Packet x_has_signbit = pcmp_eq(por(pand(x, cst_neg_inf), cst_pos_inf), cst_neg_inf);
+  const Packet x_is_neg = pandnot(x_has_signbit, abs_x_is_zero);
+  const Packet x_is_neg_zero = pand(x_has_signbit, abs_x_is_zero);
+
+  if (exponent_is_nan) {
+    return pselect(pandnot(abs_x_is_one, x_is_neg), cst_pos_one, cst_nan);
+  }
+
+  Packet pow_is_pos_zero = pandnot(abs_x_is_zero, exp_is_neg);
+  pow_is_pos_zero = por(pow_is_pos_zero, pand(abs_x_is_gt_one, pand(exp_is_inf, exp_is_neg)));
+  pow_is_pos_zero = por(pow_is_pos_zero, pand(abs_x_is_lt_one, pandnot(exp_is_inf, exp_is_neg)));
+  pow_is_pos_zero = por(pow_is_pos_zero, pand(abs_x_is_inf, exp_is_neg));
+
+  const Packet pow_is_pos_one = pand(abs_x_is_one, exp_is_inf);
+
+  Packet pow_is_pos_inf = pand(abs_x_is_zero, exp_is_neg);
+  pow_is_pos_inf = por(pow_is_pos_inf, pand(abs_x_is_lt_one, pand(exp_is_inf, exp_is_neg)));
+  pow_is_pos_inf = por(pow_is_pos_inf, pand(abs_x_is_gt_one, pandnot(exp_is_inf, exp_is_neg)));
+  pow_is_pos_inf = por(pow_is_pos_inf, pandnot(abs_x_is_inf, exp_is_neg));
+
+  const Packet pow_is_nan = pandnot(pandnot(x_is_neg, abs_x_is_inf), exp_is_inf);
+
+  Packet result = pselect(pow_is_pos_inf, cst_pos_inf, powx);
+  result = pselect(pow_is_pos_one, cst_pos_one, result);
+  result = pselect(pow_is_pos_zero, cst_pos_zero, result);
+  result = pselect(pow_is_nan, cst_nan, result);
+  result = pselect(pandnot(abs_x_is_one, x_is_neg), cst_pos_one, result);
+  return result;
+}
+}  // end namespace unary_pow
+
+template <typename Packet, typename ScalarExponent,
+          bool BaseIsIntegerType = NumTraits<typename unpacket_traits<Packet>::type>::IsInteger,
+          bool ExponentIsIntegerType = NumTraits<ScalarExponent>::IsInteger>
+struct unary_pow_impl;
+
+template <typename Packet, typename ScalarExponent>
+struct unary_pow_impl<Packet, ScalarExponent, false, false> {
+  typedef typename unpacket_traits<Packet>::type Scalar;
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet run(const Packet& x, const ScalarExponent& exponent) {
+    const bool exponent_is_integer = (numext::isfinite)(exponent) && numext::round(exponent) == exponent;
+    if (exponent_is_integer) {
+      Packet result = unary_pow::int_pow(x, exponent);
+      result = unary_pow::handle_nonint_int_errors(x, result, exponent);
+      return result;
+    } else {
+      Packet result = unary_pow::gen_pow(x, exponent);
+      result = unary_pow::handle_nonint_nonint_errors(x, result, exponent);
+      return result;
+    }
+  }
+};
+
+template <typename Packet, typename ScalarExponent>
+struct unary_pow_impl<Packet, ScalarExponent, false, true> {
+  typedef typename unpacket_traits<Packet>::type Scalar;
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet run(const Packet& x, const ScalarExponent& exponent) {
+    Packet result = unary_pow::int_pow(x, exponent);
+    result = unary_pow::handle_nonint_int_errors(x, result, exponent);
+    return result;
+  }
+};
+
 } // end namespace internal
 } // end namespace Eigen

--- a/Eigen/src/Core/functors/UnaryFunctors.h
+++ b/Eigen/src/Core/functors/UnaryFunctors.h
@ -1070,6 +1070,70 @@ struct functor_traits<scalar_logistic_op<T> > {
  };
 };

+template <typename Scalar, typename ScalarExponent, bool BaseIsIntegerType = NumTraits<Scalar>::IsInteger,
+          bool ExponentIsIntegerType = NumTraits<ScalarExponent>::IsInteger>
+struct scalar_unary_pow_op {
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE scalar_unary_pow_op(const ScalarExponent& exponent) : m_exponent(exponent) {
+    EIGEN_STATIC_ASSERT((is_arithmetic<ScalarExponent>::value), EXPONENT_MUST_BE_ARITHMETIC);
+  }
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Scalar operator()(const Scalar& a) const {
+    EIGEN_USING_STD(pow);
+    return pow(a, m_exponent);
+  }
+
+ private:
+  const ScalarExponent m_exponent;
+  scalar_unary_pow_op() {}
+};
+
+template <typename Scalar, typename ScalarExponent>
+struct scalar_unary_pow_op<Scalar, ScalarExponent, false, false> {
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE scalar_unary_pow_op(const ScalarExponent& exponent) : m_exponent(exponent) {
+    EIGEN_STATIC_ASSERT((is_same<Scalar, ScalarExponent>::value), NON_INTEGER_EXPONENT_MUST_BE_SAME_TYPE_AS_BASE);
+    EIGEN_STATIC_ASSERT((is_arithmetic<ScalarExponent>::value), EXPONENT_MUST_BE_ARITHMETIC);
+  }
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Scalar operator()(const Scalar& a) const {
+    EIGEN_USING_STD(pow);
+    return pow(a, m_exponent);
+  }
+  template <typename Packet>
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Packet packetOp(const Packet& a) const {
+    return unary_pow_impl<Packet, ScalarExponent>::run(a, m_exponent);
+  }
+
+ private:
+  const ScalarExponent m_exponent;
+  scalar_unary_pow_op() {}
+};
+
+template <typename Scalar, typename ScalarExponent>
+struct scalar_unary_pow_op<Scalar, ScalarExponent, false, true> {
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE scalar_unary_pow_op(const ScalarExponent& exponent) : m_exponent(exponent) {
+    EIGEN_STATIC_ASSERT((is_arithmetic<ScalarExponent>::value), EXPONENT_MUST_BE_ARITHMETIC);
+  }
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Scalar operator()(const Scalar& a) const {
+    return unary_pow_impl<Scalar, ScalarExponent>::run(a, m_exponent);
+  }
+  template <typename Packet>
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Packet packetOp(const Packet& a) const {
+    return unary_pow_impl<Packet, ScalarExponent>::run(a, m_exponent);
+  }
+
+ private:
+  const ScalarExponent m_exponent;
+  scalar_unary_pow_op() {}
+};
+
+template <typename Scalar, typename ScalarExponent>
+struct functor_traits<scalar_unary_pow_op<Scalar, ScalarExponent>> {
+  enum {
+    GenPacketAccess = functor_traits<scalar_pow_op<Scalar, ScalarExponent>>::PacketAccess,
+    IntPacketAccess = !NumTraits<Scalar>::IsComplex && !NumTraits<Scalar>::IsInteger && packet_traits<Scalar>::HasMul && packet_traits<Scalar>::HasDiv && packet_traits<Scalar>::HasCmp,
+    PacketAccess = NumTraits<ScalarExponent>::IsInteger ? IntPacketAccess : (IntPacketAccess && GenPacketAccess),
+    Cost = functor_traits<scalar_pow_op<Scalar, ScalarExponent>>::Cost
+  };
+};
+
 } // end namespace internal

 } // end namespace Eigen
--- a/Eigen/src/Core/util/ForwardDeclarations.h
+++ b/Eigen/src/Core/util/ForwardDeclarations.h
@ -198,6 +198,8 @@ template<typename Scalar> struct scalar_constant_op;
 template<typename Scalar> struct scalar_identity_op;
 template<typename Scalar> struct scalar_sign_op;
 template<typename Scalar,typename ScalarExponent> struct scalar_pow_op;
+template <typename Scalar, typename ScalarExponent, bool BaseIsIntegerType, bool ExponentIsIntegerType>
+struct scalar_unary_pow_op;
 template<typename LhsScalar,typename RhsScalar=LhsScalar> struct scalar_hypot_op;
 template<typename LhsScalar,typename RhsScalar=LhsScalar> struct scalar_product_op;
 template<typename LhsScalar,typename RhsScalar=LhsScalar> struct scalar_quotient_op;
--- a/Eigen/src/plugins/ArrayCwiseBinaryOps.h
+++ b/Eigen/src/plugins/ArrayCwiseBinaryOps.h
@ -134,26 +134,6 @@ absolute_difference
  */
 EIGEN_MAKE_CWISE_BINARY_OP(pow,pow)

-#ifndef EIGEN_PARSED_BY_DOXYGEN
-EIGEN_MAKE_SCALAR_BINARY_OP_ONTHERIGHT(pow,pow)
-#else
-/** \returns an expression of the coefficients of \c *this rasied to the constant power \a exponent
-  *
-  * \tparam T is the scalar type of \a exponent. It must be compatible with the scalar type of the given expression.
-  *
-  * This function computes the coefficient-wise power. The function MatrixBase::pow() in the
-  * unsupported module MatrixFunctions computes the matrix power.
-  *
-  * Example: \include Cwise_pow.cpp
-  * Output: \verbinclude Cwise_pow.out
-  *
-  * \sa ArrayBase::pow(ArrayBase), square(), cube(), exp(), log()
-  */
-template<typename T>
-const CwiseBinaryOp<internal::scalar_pow_op<Scalar,T>,Derived,Constant<T> > pow(const T& exponent) const;
-#endif
-
-
 // TODO code generating macros could be moved to Macros.h and could include generation of documentation
 #define EIGEN_MAKE_CWISE_COMP_OP(OP, COMPARATOR) \
 template<typename OtherDerived> \
--- a/Eigen/src/plugins/ArrayCwiseUnaryOps.h
+++ b/Eigen/src/plugins/ArrayCwiseUnaryOps.h
@ -694,3 +694,32 @@ ndtri() const
 {
  return NdtriReturnType(derived());
 }
+
+template <typename ScalarExponent>
+using UnaryPowReturnType =
+    std::enable_if_t<internal::is_arithmetic<ScalarExponent>::value,
+                     CwiseUnaryOp<internal::scalar_unary_pow_op<Scalar, ScalarExponent>, const Derived>>;
+
+#ifndef EIGEN_PARSED_BY_DOXYGEN
+template <typename ScalarExponent>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const UnaryPowReturnType<ScalarExponent> pow(
+    const ScalarExponent& exponent) const {
+  return UnaryPowReturnType<ScalarExponent>(derived(), internal::scalar_unary_pow_op<Scalar, ScalarExponent>(exponent));
+#else
+/** \returns an expression of the coefficients of \c *this rasied to the constant power \a exponent
+ *
+ * \tparam T is the scalar type of \a exponent. It must be compatible with the scalar type of the given expression.
+ *
+ * This function computes the coefficient-wise power. The function MatrixBase::pow() in the
+ * unsupported module MatrixFunctions computes the matrix power.
+ *
+ * Example: \include Cwise_pow.cpp
+ * Output: \verbinclude Cwise_pow.out
+ *
+ * \sa ArrayBase::pow(ArrayBase), square(), cube(), exp(), log()
+ */
+template <typename ScalarExponent>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const UnaryPowReturnType<ScalarExponent> pow(
+    const ScalarExponent& exponent) const;
+#endif
+}
--- a/Eigen/src/plugins/MatrixCwiseUnaryOps.h
+++ b/Eigen/src/plugins/MatrixCwiseUnaryOps.h
@ -93,3 +93,13 @@ EIGEN_DOC_UNARY_ADDONS(cwiseArg,arg)
 EIGEN_DEVICE_FUNC
 inline const CwiseArgReturnType
 cwiseArg() const { return CwiseArgReturnType(derived()); }
+
+template <typename ScalarExponent>
+using CwisePowReturnType =
+    std::enable_if_t<internal::is_arithmetic<ScalarExponent>::value,
+                     CwiseUnaryOp<internal::scalar_unary_pow_op<Scalar, ScalarExponent>, const Derived>>;
+
+template <typename ScalarExponent>
+EIGEN_DEVICE_FUNC inline const CwisePowReturnType<ScalarExponent> cwisePow(const ScalarExponent& exponent) const {
+  return CwisePowReturnType<ScalarExponent>(derived(), internal::scalar_unary_pow_op<Scalar, ScalarExponent>(exponent));
+}
--- a/test/array_cwise.cpp
+++ b/test/array_cwise.cpp
@ -79,6 +79,50 @@ void pow_test() {
      }
    }
  }
+
+  typedef typename internal::make_integer<Scalar>::type Int_t;
+
+  // ensure both vectorized and non-vectorized paths taken
+  Index test_size = 2 * internal::packet_traits<Scalar>::size + 1;
+  
+  Array<Scalar, Dynamic, 1> eigenPow(test_size);
+  for (int i = 0; i < num_cases; ++i) {
+    Array<Scalar, Dynamic, 1> bases = x.col(i);
+    for (Scalar abs_exponent : abs_vals){
+      for (Scalar exponent : {-abs_exponent, abs_exponent}){
+        // test floating point exponent code path
+        eigenPow.setZero();
+        eigenPow = bases.pow(exponent);
+        for (int j = 0; j < num_repeats; j++){
+          Scalar e = static_cast<Scalar>(std::pow(bases(j), exponent));
+          Scalar a = eigenPow(j);
+          bool success = (a == e) || ((numext::isfinite)(e) && internal::isApprox(a, e, tol)) || ((numext::isnan)(a) && (numext::isnan)(e));
+          all_pass &= success;
+          if (!success) {
+            std::cout << "pow(" << x(i, j) << "," << y(i, j) << ")   =   " << a << " !=  " << e << std::endl;
+          }
+        }
+        // test integer exponent code path
+        bool exponent_is_integer = (numext::isfinite)(exponent) && (numext::round(exponent) == exponent) && (numext::abs(exponent) < static_cast<Scalar>(NumTraits<Int_t>::highest()));
+        if (exponent_is_integer)
+        {
+          Int_t exponent_as_int = static_cast<Int_t>(exponent);
+          eigenPow.setZero();
+          eigenPow = bases.pow(exponent_as_int);
+          for (int j = 0; j < num_repeats; j++){
+            Scalar e = static_cast<Scalar>(std::pow(bases(j), exponent));
+            Scalar a = eigenPow(j);
+            bool success = (a == e) || ((numext::isfinite)(e) && internal::isApprox(a, e, tol)) || ((numext::isnan)(a) && (numext::isnan)(e));
+            all_pass &= success;
+            if (!success) {
+              std::cout << "pow(" << x(i, j) << "," << y(i, j) << ")   =   " << a << " !=  " << e << std::endl;
+            }
+          }
+        }
+      }
+    }
+  }
+
  VERIFY(all_pass);
 }

--- a/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h
@ -331,10 +331,12 @@ class TensorBase<Derived, ReadOnlyAccessors>
      return choose(Cond<NumTraits<CoeffReturnType>::IsComplex>(), unaryExpr(internal::scalar_conjugate_op<Scalar>()), derived());
    }

-    EIGEN_DEVICE_FUNC
-    EIGEN_STRONG_INLINE const TensorCwiseUnaryOp<internal::bind2nd_op<internal::scalar_pow_op<Scalar,Scalar> >, const Derived>
-    pow(Scalar exponent) const {
-      return unaryExpr(internal::bind2nd_op<internal::scalar_pow_op<Scalar,Scalar> >(exponent));
+    template<typename ScalarExponent>
+    EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const std::enable_if_t<internal::is_arithmetic<ScalarExponent>::value,
+        TensorCwiseUnaryOp<internal::scalar_unary_pow_op<Scalar, ScalarExponent>, const Derived>>
+        pow(ScalarExponent exponent) const
+    {
+        return unaryExpr(internal::scalar_unary_pow_op<Scalar, ScalarExponent>(exponent));
    }

    EIGEN_DEVICE_FUNC