axpby.hpp

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#pragma once

#include <cute/config.hpp>

#include <cute/tensor.hpp>
#include <cute/tensor_predicate.hpp>

namespace cute
{

//
// Accept mutable temporaries
//
template <class Alpha,
          class XEngine, class XLayout,
          class Beta,
          class YEngine, class YLayout,
          class PrdTensor = TrivialPredTensor>
CUTE_HOST_DEVICE
void
axpby(Alpha                    const& alpha,
      Tensor<XEngine, XLayout> const& x,
      Beta                     const& beta,
      Tensor<YEngine, YLayout>     && y,
      PrdTensor                const& p = {})
{
  return axpby(alpha, x, beta, y, p);
}

//
// AXPBY
//
template <class Alpha,
          class XEngine, class XLayout,
          class Beta,
          class YEngine, class YLayout,
          class PrdTensor = TrivialPredTensor>
CUTE_HOST_DEVICE
void
axpby(Alpha                    const& alpha,
      Tensor<XEngine, XLayout> const& x,
      Beta                     const& beta,
      Tensor<YEngine, YLayout>      & y,
      PrdTensor                const& p = {})
{
  auto isBetaZero = [&] () {
    if constexpr (is_complex<Beta>::value) {
      return beta.real() == Int<0>{} && beta.imag() == Int<0>{};
    }
    else {
      return beta == Int<0>{};
    }

    CUTE_GCC_UNREACHABLE;
  } ();

  CUTE_UNROLL
  for (int i = 0; i < size(x); ++i) {
    if (p(i)) {
      y(i) = (isBetaZero ? alpha * x(i) : alpha * x(i) + beta * y(i));
    }
  }
}

} // end namespace cute