std::experi...s_simd_mask(3)

🌸 std::experimental::is_simd, std::experimental::is_simd_mask 🌸

okay bestie so this is from the C++ Standard Libary manual, section 3, and it's genuinely one of those pages where the whole personality is "am I a SIMD type or not" — and honestly? iconic. Let's get into it 💅

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✨ NAME ✨

std::experimental::is_simd, std::experimental::is_simd_mask — literally just std::experimental::is_simd, std::experimental::is_simd_mask. That's the name. Periodt 🫶

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✨ SYNOPSIS ✨

so this whole thing lives in the header <experimental/simd> 🎀

template< class T >                   (1) (parallelism TS v2)
struct is_simd;
template< class T >                   (2) (parallelism TS v2)
struct is_simd_mask;

1. bestie, if T is a specialization of the simd class template, then this provides the member constant value equal true. For literally any other type, value is false. that's the whole job 💖
2. and if T is a specialization of the simd_mask class template, it provides the member constant value equal true. For any other type, value is false. slay ✨

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✨ TEMPLATE PARAMETERS ✨

• T — a type to check 👀

🌈 Helper variable template 🌈

template< class T >
(parallelism TS v2)
inline constexpr bool is_simd_v = is_simd<T>::value;
template< class T >
(parallelism TS v2)
inline constexpr bool is_simd_mask_v = is_simd_mask<T>::value;

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✨ INHERITED FROM std::integral_constant ✨

🦋 Member constants 🦋

• value — true if T is a simd/simd_mask type, false otherwise. [static] (public static member constant) ⭐

🦋 Member functions 🦋

• operator bool — converts the object to bool, returns value (public member function) 💜
• operator() — returns value (C++14) (public member function) 💜

🦋 Member types 🦋

• value_type → bool
• type → std::integral_constant<bool, value>

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🎀 NOTES 🎀

okay this is the part you actually need to read, ngl. is_simd_v<T> is necessary but not sufficient for testing whether T can be used as a SIMD type 😭

for example, is_simd_v<simd<bool>> is true, even though bool is not included in the permissible vectorizable types. the missing condition is std::is_constructible_v<T>, which is false for simd<bool>. so yeah — vibe check twice, bestie 💀

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🔥 EXAMPLE 🔥

// Run this code

#include <experimental/simd>
#include <iostream>
#include <string_view>

namespace stdx = std::experimental;

template<typename T>
void test_simd(std::string_view type_name)
{
    std::cout << std::boolalpha
              << "Type: " << type_name << '\n'
              << "  is_simd: " << stdx::is_simd_v<T> << '\n'
              << "  is_constructible: " << std::is_constructible_v<T> << '\n';
}

template<typename T>
void test_simd_mask(std::string_view type_name)
{
    std::cout << std::boolalpha
              << "Type: " << type_name << '\n'
              << "  is_simd_mask: " << stdx::is_simd_mask_v<T> << '\n'
              << "  is_constructible: " << std::is_constructible_v<T> << "\n\n";
}

int main()
{
    test_simd<int>("int");
    test_simd_mask<int>("int");

    test_simd<stdx::simd<float>>("simd<float>");
    test_simd_mask<stdx::simd_mask<float>>("simd_mask<float>");

    test_simd<stdx::simd<bool>>("simd<bool>");
    test_simd_mask<stdx::simd_mask<bool>>("simd_mask<bool>");
}

⭐ Output ⭐

Type: int
  is_simd: false
  is_constructible: true
Type: int
  is_simd_mask: false
  is_constructible: true

Type: simd<float>
  is_simd: true
  is_constructible: true
Type: simd_mask<float>
  is_simd_mask: true
  is_constructible: true

Type: simd<bool>
  is_simd: true
  is_constructible: false
Type: simd_mask<bool>
  is_simd_mask: true
  is_constructible: false

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see how simd<bool> is like "yes I'm a simd" but "no I'm not constructible"? that's the whole note. that's the drama. i told you so 🙈

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and that's the page!! 💖✨🎀🦋🌸💅🫶 sourced from http://cppreference.com, dated 2024.06.10, and yeah that's the std::experi...s_simd_mask(3) footer — go forth and type-trait responsibly, bestie 👑