std::experimental:: where_expression

The class template where_expression abstracts the notion of selected elements of a given lvalue of arithmetic or data-parallel type. Selected elements are the elements of the lvalue (of type V ) for which the corresponding element of the mask (of type M ) is true. Operators applied to objects of type where_expression<M, V> are applied only to selected elements. All other elements are left unchanged.

Use the where function to construct where_expression objects.

Template parameters

Valid combinations of ( M , V ) are:

• ( simd_mask < T, Abi > , simd < T, Abi > ) ,
• ( simd_mask < T, Abi > , simd_mask < T, Abi > ) ,
• ( bool , T ) .

Member functions

Example

#include <cstddef>
#include <experimental/simd>
#include <iostream>
namespace stdx = std::experimental;
 
void print(auto const& a)
{
    for (std::size_t i{}; i != std::size(a); ++i)
        std::cout << a[i] << ' ';
    std::cout << '\n';
}
 
template<class A>
stdx::simd<int, A> my_abs(stdx::simd<int, A> x)
{
    where(x < 0, x) = -x;
    return x;
}
 
int main()
{
    const stdx::native_simd<int> a([](int i) { return i - 2; });
    print(a);
    const auto b = my_abs(a);
    print(b);
}

-2 -1 0 1 
2 1 0 1