Matrix product always falls back to native implementation #248
Description
I am trying to implement HPX backend for matrix_product.
I am not certainly clear with this section of code (below).
The following always evalutes to false right ?
Because both qualified lookup and unqualified lookup of matrix_product return void, so the second part of the expression always evaluates to false and hence whole std::enable_if_t is false.
template <class Exec, class A_t, class B_t, class C_t>
struct is_custom_matrix_product_avail<
Exec, A_t, B_t, C_t,
std::enable_if_t<
std::is_void_v<
decltype(
matrix_product(
std::declval<Exec>(),
std::declval<A_t>(),
std::declval<B_t>(),
std::declval<C_t>()))
>
&& !std::is_same_v< // see #218
decltype(
std::experimental::linalg::matrix_product(
std::declval<Exec>(),
std::declval<A_t>(),
std::declval<B_t>(),
std::declval<C_t>())),
decltype(
matrix_product(
std::declval<Exec>(),
std::declval<A_t>(),
std::declval<B_t>(),
std::declval<C_t>()))
>
&& !linalg::impl::is_inline_exec_v<Exec>
>
>
: std::true_type{};Which makes this : https://github.com/kokkos/stdBLAS/blob/main/include/experimental/__p1673_bits/blas3_matrix_product.hpp#L757 always false and hence falls backs to native sequential implementation.