cutlass/cutlass/fragment_multiply_add.h

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/*! \file
    \brief Defines multiply-add operations on fragments within a thread.
*/
#pragma once

#include <cutlass/fragment.h>

namespace cutlass {
namespace gemm {

////////////////////////////////////////////////////////////////////////////////////////////////////

template <typename Scalar_>
struct FragmentMultiplyAdd {
  /// The shape of the instruction.
  typedef Shape<1, 1, 1, 1> InstructionShape;
  /// The type for A.
  typedef Scalar_ ScalarA;
  /// The type for B.
  typedef Scalar_ ScalarB;
  /// The type for C and D.
  typedef Scalar_ ScalarC;

  /// Ctor.
  CUTLASS_DEVICE FragmentMultiplyAdd() {}

  /// Multiply : d = a*b.
  template <typename FragmentB_, typename FragmentCd_>
  CUTLASS_DEVICE void multiply(Scalar_ a, FragmentB_ const& b, FragmentCd_& d) {
    int const kReduction = FragmentB_::kElements / FragmentCd_::kElements;
    for (int j = 0; j < FragmentCd_::kElements; ++j) {
      d[j] = a * b[j * kReduction + 0];
      for (int k = 1; k < kReduction; ++k) {
        d[j] += a * b[j * kReduction + k];
      }
    }
  }

  /// Multiply : d = a*b + c.
  template <typename FragmentB_, typename FragmentCd_>
  CUTLASS_DEVICE void multiply_add(Scalar_ a,
                                   FragmentB_ const& b,
                                   FragmentCd_ const& c,
                                   FragmentCd_& d) {
    int const kReduction = FragmentB_::kElements / FragmentCd_::kElements;
    for (int j = 0; j < FragmentCd_::kElements; ++j) {
      d[j] = a * b[j * kReduction + 0] + c[j];
      for (int k = 1; k < kReduction; ++k) {
        d[j] += a * b[j * kReduction + k];
      }
    }
  }
};

////////////////////////////////////////////////////////////////////////////////////////////////////

#if !defined(__CUDACC_RTC__) || defined(CUTLASS_NVRTC_HAS_FP16)
template <>
struct FragmentMultiplyAdd<half> {
  /// The shape of the instruction.
  typedef Shape<1, 1, 2, 1> InstructionShape;
  /// The type for A.
  typedef half ScalarA;
  /// The type for B.
  typedef half ScalarB;
  /// The type for C and D.
  typedef half ScalarC;

  /// Ctor.
  CUTLASS_DEVICE FragmentMultiplyAdd() {}

  /// Multiply : d = a*b.
  template <typename FragmentB_, typename FragmentCd_>
  CUTLASS_DEVICE void multiply(half a, FragmentB_ const& b, FragmentCd_& d) {
#if defined(__CUDACC__) && __CUDA_ARCH__ >= 530

    // Assemble a half2 from a.
    __half2 const a_half2 = __half2half2(a);
    // The input.
    __half2 const* b_half2 = reinterpret_cast<__half2 const*>(&b[0]);
    // The output.
    __half2* d_half2 = reinterpret_cast<__half2*>(&d[0]);

    int const kReduction = FragmentB_::kElements / FragmentCd_::kElements;
    for (int j = 0; j < FragmentCd_::kElements / 2; ++j) {
      d_half2[j] = __hmul2(a_half2, b_half2[j * kReduction + 0]);
      for (int k = 1; k < kReduction; ++k) {
        d_half2[j] = __hfma2(a_half2, b_half2[j * kReduction + k], d_half2[j]);
      }
    }
#endif
  }

  /// Multiply : d = a*b + c.
  template <typename FragmentB_, typename FragmentCd_>
  CUTLASS_DEVICE void multiply_add(half a,
                                   FragmentB_ const& b,
                                   FragmentCd_ const& c,
                                   FragmentCd_& d) {
#if defined(__CUDACC__) && __CUDA_ARCH__ >= 530
    // Assemble a half2 from a.
    __half2 const a_half2 = __half2half2(a);
    // The inputs.
    __half2 const* b_half2 = reinterpret_cast<__half2 const*>(&b[0]);
    __half2 const* c_half2 = reinterpret_cast<__half2 const*>(&c[0]);
    // The output.
    __half2* d_half2 = reinterpret_cast<__half2*>(&d[0]);

    int const kReduction = (FragmentB_::kElements / FragmentCd_::kElements);
    for (int j = 0; j < FragmentCd_::kElements / 2; ++j) {
      d_half2[j] = __hfma2(a_half2, b_half2[j * kReduction + 0], c_half2[j]);
      for (int k = 1; k < kReduction; ++k) {
        d_half2[j] = __hfma2(a_half2, b_half2[j * kReduction + k], d_half2[j]);
      }
    }
#endif
  }
};

#endif

////////////////////////////////////////////////////////////////////////////////////////////////////

}  // namespace gemm
}  // namespace cutlass