29 Numerics library [numerics]

29.10 Data-parallel types [simd]

29.10.6 Class template basic_simd [simd.class]

29.10.6.2 basic_simd constructors [simd.ctor]

template<class U> constexpr explicit(see below) basic_simd(U&& value) noexcept;

Let From denote the type remove_cvref_t<U>.

Constraints: value_type satisfies constructible_from<U>.

Effects: Initializes each element to the value of the argument after conversion to value_type.

Remarks: The expression inside explicit evaluates to false if and only if U satisfies convertible_to<value_type>, and either

(4.1)
From is not an arithmetic type and does not satisfy constexpr-wrapper-like,
(4.2)
From is an arithmetic type and the conversion from From to value_type is value-preserving ([simd.general]), or
(4.3)
From satisfies constexpr-wrapper-like, remove_const_t<decltype(From::value)> is an arithmetic type, and From::value is representable by value_type.

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template<class U, class UAbi>
  constexpr explicit(see below) basic_simd(const basic_simd<U, UAbi>& x) noexcept;

Constraints: simd-size-v<U, UAbi> == size() is true.

Effects: Initializes the

i^{th}

element with static_cast<T>(x[i]) for all i in the range of [0, size()).

Remarks: The expression inside explicit evaluates to true if either

(7.1)
the conversion from U to value_type is not value-preserving, or
(7.2)
both U and value_type are integral types and the integer conversion rank ([conv.rank]) of U is greater than the integer conversion rank of value_type, or
(7.3)
both U and value_type are floating-point types and the floating-point conversion rank ([conv.rank]) of U is greater than the floating-point conversion rank of value_type.

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template<class G> constexpr explicit basic_simd(G&& gen);

Let From

_{i}

denote the type decltype(gen(integral_constant<simd-size-type, i>())).

Constraints: From

_{i}

satisfies convertible_to<value_type> for all i in the range of [0, size()).

In addition, for all i in the range of [0, size()), if From

_{i}

is an arithmetic type, conversion from From

_{i}

to value_type is value-preserving.

Effects: Initializes the

i^{th}

element with static_cast<value_type>(gen(integral_constant<simd-size-type, i>())) for all i in the range of [0, size()).

Remarks: gen is invoked exactly once for each i, in increasing order of i.

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template<class R, class... Flags>
  constexpr basic_simd(R&& r, flags<Flags...> = {});
template<class R, class... Flags>
  constexpr basic_simd(R&& r, const mask_type& mask, flags<Flags...> = {});

Let mask be mask_type(true) for the overload with no mask parameter.

Constraints:

(13.1)
R models ranges::contiguous_range and ranges::sized_range,
(13.2)
ranges::size(r) is a constant expression, and
(13.3)
ranges::size(r) is equal to size().

Mandates:

(14.1)
ranges::range_value_t<R> is a vectorizable type, and
(14.2)
if the template parameter pack Flags does not contain convert-flag, then the conversion from ranges::range_value_t<R> to value_type is value-preserving.

Preconditions:

(15.1)
If the template parameter pack Flags contains aligned-flag, ranges::data(r) points to storage aligned by alignment_v<basic_simd, ranges::range_value_t<R>>.
(15.2)
If the template parameter pack Flags contains overaligned-flag<N>, ranges::data(r) points to storage aligned by N.

Effects: Initializes the

i^{th}

element with mask[i] ? static_cast<T>(ranges::data(r)[i]) : T() for all i in the range of [0, size()).

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template<class R, class... Ts>
  basic_simd(R&& r, Ts...) -> see below;

Constraints:

(17.1)
R models ranges::contiguous_range and ranges::sized_range, and
(17.2)
ranges::size(r) is a constant expression.

Remarks: The deduced type is equivalent to simd<ranges::range_value_t<R>, ranges::size(r)>.

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template<simd-floating-point V>
  constexpr explicit(see below)
    basic_simd(const V& reals, const V& imags = {}) noexcept;

Constraints:

(19.1)
simd-complex<basic_simd> is modeled, and
(19.2)
V::size() == size() is true.

Effects: Initializes the

i^{th}

element with value_type(reals[i], imags[i]) for all i in the range [0, size()).

Remarks: The expression inside explicit evaluates to false if and only if the floating-point conversion rank of T::value_type is greater than or equal to the floating-point conversion rank of V::value_type.