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/*! \file
    \brief Specialization implementing multiply-add operation on half-precision floating point
   fragments.
*/
#pragma once

#include <cutlass/fragment.h>

#include <cutlass/gemm/thread_multiply_add.h>

namespace cutlass {
namespace gemm {

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

/// Template performing matrix multiply-add operation within a thread
template <typename AccumulatorsPerThread_, typename ThreadsPerWarp_>
struct ThreadMultiplyAdd<AccumulatorsPerThread_, ThreadsPerWarp_, half, half, half> {
  /// The shape of the instruction.
  typedef Shape<1, 1, 2, 1> InstructionShape;
  /// The number of accumulators per thread.
  typedef AccumulatorsPerThread_ AccumulatorsPerThread;
  /// The number of threads per warp.
  typedef ThreadsPerWarp_ ThreadsPerWarp;
  /// The number of accumulators per warp.
  typedef typename ShapeMul<AccumulatorsPerThread, ThreadsPerWarp>::Shape AccumulatorsPerWarp;
  /// The type for A.
  typedef half ScalarA;
  /// The fragment for A.
  typedef Fragment<ScalarA, AccumulatorsPerThread::kW> FragmentA;
  /// The type for B.
  typedef half ScalarB;
  /// The fragment for B.
  typedef Fragment<ScalarB, AccumulatorsPerThread::kH> FragmentB;
  /// The type for C and D.
  typedef half ScalarC;
  /// The accumulators.
  typedef Fragment<half, AccumulatorsPerThread::kH * AccumulatorsPerThread::kW> Accumulators;

  /// Make sure there's an even number of elements in both dimensions.
  static_assert(AccumulatorsPerThread::kH % 2 == 0, "Invalid size");
  static_assert(AccumulatorsPerThread::kW % 2 == 0, "Invalid size");

  /// Ctor.
  CUTLASS_DEVICE ThreadMultiplyAdd() {}

  /// Multiply : d = a*b + c.
  CUTLASS_DEVICE void multiply_add(FragmentA const& a,
                                   FragmentB const& b,
                                   Accumulators const& c,
                                   Accumulators& d) {
#if defined(__CUDACC__) && __CUDA_ARCH__ >= 530
    // The inputs.
    __half2 const* a_half2 = reinterpret_cast<__half2 const*>(&a[0]);
    __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]);

    for (int j = 0; j < AccumulatorsPerThread::kH / 2; ++j) {
      for (int i = 0; i < AccumulatorsPerThread::kW / 2; ++i) {
        // The offsets in the output fragment.
        int const k0 = (2 * j + 0) * (AccumulatorsPerThread::kW / 2) + i;
        int const k1 = (2 * j + 1) * (AccumulatorsPerThread::kW / 2) + i;

        // Compute the product a[i] * b[j].H0_H0.
        d_half2[k0] = __hfma2(a_half2[i], __low2half2(b_half2[j]), c_half2[k0]);
        // Compute the product a[i] * b[j].H1_H1.
        d_half2[k1] = __hfma2(a_half2[i], __high2half2(b_half2[j]), c_half2[k1]);
      }
    }
#endif
  }
};

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

}  // namespace gemm
}  // namespace cutlass
