29 Numerics library [numerics]

29.10 Data-parallel types [simd]

29.10.7 basic_simd non-member operations [simd.nonmembers]

29.10.7.5 basic_simd reductions [simd.reductions]

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template<class T, class Abi, class BinaryOperation = plus<>> constexpr T reduce(const basic_simd<T, Abi>& x, BinaryOperation binary_op = {});
1
#
Constraints: BinaryOperation models reduction-binary-operation<T>.
2
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Preconditions: binary_op does not modify x.
3
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Returns: GENERALIZED_SUM(binary_op, simd<T, 1>(x[0]), …, simd<T, 1>(x[x.size() - 1])​)[0] ([numerics.defns]).
4
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Throws: Any exception thrown from binary_op.
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template<class T, class Abi, class BinaryOperation = plus<>> constexpr T reduce( const basic_simd<T, Abi>& x, const typename basic_simd<T, Abi>::mask_type& mask, BinaryOperation binary_op = {}, type_identity_t<T> identity_element = see below);
5
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Constraints:
  • (5.1)
    BinaryOperation models reduction-binary-operation<T>.
  • (5.2)
    An argument for identity_element is provided for the invocation, unless BinaryOperation is one of plus<>, multiplies<>, bit_and<>, bit_or<>, or bit_xor<>.
6
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Preconditions:
  • (6.1)
    binary_op does not modify x.
  • (6.2)
    For all finite values y representable by T, the results of y == binary_op(simd<T, 1>(identity_element), simd<T, 1>(y))[0] and y == binary_op(simd<T, 1>(y), simd<T, 1>(identity_element))[0] are true.
7
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Returns: If none_of(mask) is true, returns identity_element.
Otherwise, returns GENERALIZED_SUM(binary_op, simd<T, 1>(x[]), …, simd<T, 1>(x[]))[0] where are the selected indices of mask.
8
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Throws: Any exception thrown from binary_op.
9
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Remarks: The default argument for identity_element is equal to
  • (9.1)
    T() if BinaryOperation is plus<>,
  • (9.2)
    T(1) if BinaryOperation is multiplies<>,
  • (9.3)
    T(~T()) if BinaryOperation is bit_and<>,
  • (9.4)
    T() if BinaryOperation is bit_or<>, or
  • (9.5)
    T() if BinaryOperation is bit_xor<>.
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template<class T, class Abi> constexpr T reduce_min(const basic_simd<T, Abi>& x) noexcept;
10
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Constraints: T models totally_ordered.
11
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Returns: The value of an element x[j] for which x[i] < x[j] is false for all i in the range of [0, basic_simd<T, Abi>​::​size()).
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template<class T, class Abi> constexpr T reduce_min( const basic_simd<T, Abi>&, const typename basic_simd<T, Abi>::mask_type&) noexcept;
12
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Constraints: T models totally_ordered.
13
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Returns: If none_of(mask) is true, returns numeric_limits<T>​::​max().
Otherwise, returns the value of a selected element x[j] for which x[i] < x[j] is false for all selected indices i of mask.
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template<class T, class Abi> constexpr T reduce_max(const basic_simd<T, Abi>& x) noexcept;
14
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Constraints: T models totally_ordered.
15
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Returns: The value of an element x[j] for which x[j] < x[i] is false for all i in the range of [0, basic_simd<T, Abi>​::​size()).
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template<class T, class Abi> constexpr T reduce_max( const basic_simd<T, Abi>&, const typename basic_simd<T, Abi>::mask_type&) noexcept;
16
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Constraints: T models totally_ordered.
17
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Returns: If none_of(mask) is true, returns numeric_limits<V​::​value_type>​::​lowest().
Otherwise, returns the value of a selected element x[j] for which x[j] < x[i] is false for all selected indices i of mask.