reverse_in_subgroups

auto eve::reverse_in_subgroups = detail::named_shuffle_1<reverse_in_subgroups_t> {}

inlineconstexpr

Defined in Header

#include <eve/module/core.hpp>

As any named shuffle, allows to pass a group size, to treat multiple elements as one. Group size has to be 0 < G <= T::size() Subgroup size has to be 1 <= SubG <= T::size() / G

Note

SubG == T::size() makes this function equivalent eve::reverse.

template <simd_value T, std::ptrdiff_t G, std::ptrdiff_t SubG>
T reverse_in_subgroups(T x, eve::fixed<G>, eve::fixed<SubG>);  // (1)
 
template <simd_value T, std::ptrdiff_t SubG>
T reverse_in_subgroups(T x, eve::fixed<SubG>); // (2)

Parameters

• x - simd_value to shuffle
• G - (optional) - number of elements to treat as one.
• SubG - size of a subgroup

(2) calls (1) with G == 1; (1) within each SubG reverses positions elements

Return value

Returns x where each subgroup is reversed.

Example

#include <eve/module/core.hpp>
 
#include <tts/tts.hpp>
 
using w_t = eve::wide<std::uint32_t, eve::fixed<4>>;
 
int
main()
{
  w_t x {0, 1, 2, 3};
 
  TTS_EXPECT(eve::all(w_t {0, 1, 2, 3} == eve::reverse_in_subgroups(x, eve::lane<1>)));
  TTS_EXPECT(eve::all(w_t {1, 0, 3, 2} == eve::reverse_in_subgroups(x, eve::lane<2>)));
  TTS_EXPECT(eve::all(w_t {3, 2, 1, 0} == eve::reverse_in_subgroups(x, eve::lane<4>)));
 
  TTS_EXPECT(
      eve::all(w_t {2, 3, 0, 1} == eve::reverse_in_subgroups(x, eve::lane<2>, eve::lane<2>)));
}