flash-attention/csrc/cutlass/include/cute/numeric/complex.hpp

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#pragma once

#include <cutlass/complex.h>
#include <cute/util/type_traits.hpp>
#include <cute/numeric/numeric_types.hpp>

namespace cute
{

using cutlass::complex;
using cutlass::is_complex;
using cutlass::RealType;
using cutlass::real;
using cutlass::imag;
using cutlass::conj;

template <class T>
static constexpr auto is_complex_v = is_complex<T>::value;

/// Fused multiply-add for complex numbers
template <class T>
CUTE_HOST_DEVICE constexpr
void
fma(complex<T>      & d,
    complex<T> const& a,
    complex<T> const& b,
    complex<T> const& c)
{
  fma(d.real(),  a.real(), b.real(), c.real());
  fma(d.imag(),  a.real(), b.imag(), c.imag());
  fma(d.real(), -a.imag(), b.imag(), d.real());
  fma(d.imag(),  a.imag(), b.real(), d.imag());
}

/// Fused multiply-add for triplets
template <class T>
CUTE_HOST_DEVICE constexpr
void
fma(complex<T> const& a,
    complex<T> const& b,
    complex<T>      & c)
{
  return fma(c, a, b, c);
}

} // end namespace cute