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

// File:        dotproductavx.cpp

// Description: Architecture-specific dot-product function.

// Author:      Ray Smith

//

// (C) Copyright 2015, Google Inc.

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

// http://www.apache.org/licenses/LICENSE-2.0

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

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

#if !defined(__AVX__)

#  if defined(__i686__) || defined(__x86_64__)

#    error Implementation only for AVX capable architectures

#  endif

#else

#  include <immintrin.h>

#  include <cstdint>

#  include "dotproduct.h"

namespace tesseract {

// Computes and returns the dot product of the n-vectors u and v.

// Uses Intel AVX intrinsics to access the SIMD instruction set.

#if defined(FAST_FLOAT)

float DotProductAVX(const float *u, const float *v, int n) {

  const unsigned quot = n / 8;

  const unsigned rem = n % 8;

  __m256 t0 = _mm256_setzero_ps();

  for (unsigned k = 0; k < quot; k++) {

    __m256 f0 = _mm256_loadu_ps(u);

    __m256 f1 = _mm256_loadu_ps(v);

    f0 = _mm256_mul_ps(f0, f1);

    t0 = _mm256_add_ps(t0, f0);

    u += 8;

    v += 8;

  }

  alignas(32) float tmp[8];

  _mm256_store_ps(tmp, t0);

  float result = tmp[0] + tmp[1] + tmp[2] + tmp[3] + tmp[4] + tmp[5] + tmp[6] + tmp[7];

  for (unsigned k = 0; k < rem; k++) {

    result += *u++ * *v++;

  }

  return result;

}

#else

double DotProductAVX(const double *u, const double *v, int n) {

  const unsigned quot = n / 8;

  const unsigned rem = n % 8;

  __m256d t0 = _mm256_setzero_pd();

  __m256d t1 = _mm256_setzero_pd();

  for (unsigned k = 0; k < quot; k++) {

    __m256d f0 = _mm256_loadu_pd(u);

    __m256d f1 = _mm256_loadu_pd(v);

    f0 = _mm256_mul_pd(f0, f1);

    t0 = _mm256_add_pd(t0, f0);

    u += 4;

    v += 4;

    __m256d f2 = _mm256_loadu_pd(u);

    __m256d f3 = _mm256_loadu_pd(v);

    f2 = _mm256_mul_pd(f2, f3);

    t1 = _mm256_add_pd(t1, f2);

    u += 4;

    v += 4;

  }

  t0 = _mm256_hadd_pd(t0, t1);

  alignas(32) double tmp[4];

  _mm256_store_pd(tmp, t0);

  double result = tmp[0] + tmp[1] + tmp[2] + tmp[3];

  for (unsigned k = 0; k < rem; k++) {

    result += *u++ * *v++;

  }

  return result;

}

#endif

} // namespace tesseract.

#endif