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///////////////////////////////////////////////////////////////////////
// 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__)
/* willus mode -- don't throw an error -- just skip */
/*
# 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
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