chundoong-lab-ta/SHPC2022/hw2/vectordot/vectordot.c

#include <immintrin.h>
#include <math.h>

float vectordot_naive(float *A, float *B, int N) {
  float c = 0.f;
  for (int i = 0; i < N; ++i) {
    c += A[i] * B[i];
  }
  return c;
}

float vectordot_fma(float *A, float *B, int N) {
  float c = 0.f;
  /*
  TODO: FILL IN HERE
  */

  __m256 sum = _mm256_setzero_ps();
  for (int i = 0; i < N; i = i + 8) {
    __m256 A_ = _mm256_load_ps(A + i);
    __m256 B_ = _mm256_load_ps(B + i);
    sum = _mm256_fmadd_ps(A_, B_, sum);
  }
  const __m128 hiQuad = _mm256_extractf128_ps(sum, 1);
  const __m128 loQuad = _mm256_castps256_ps128(sum);
  const __m128 sumQuad = _mm_add_ps(loQuad, hiQuad);

  const __m128 loDual = sumQuad;
  const __m128 hiDual = _mm_movehl_ps(sumQuad, sumQuad);
  const __m128 sumDual = _mm_add_ps(loDual, hiDual);

  const __m128 lo = sumDual;
  const __m128 hi = _mm_shuffle_ps(sumDual, sumDual, 0x1);
  const __m128 res = _mm_add_ss(lo, hi);

  c = _mm_cvtss_f32(res);

  return c;
}