float fvec_inner_product()

in lattices/lattice_utils.cpp [259:291]

• 28 lines of code
• 4 McCabe index (conditional complexity)

float fvec_inner_product (const float * x,
                          const float * y,
                          size_t d)
{
    __m256 msum1 = _mm256_setzero_ps();

    while (d >= 8) {
        __m256 mx = _mm256_loadu_ps (x); x += 8;
        __m256 my = _mm256_loadu_ps (y); y += 8;
        msum1 = _mm256_add_ps (msum1, _mm256_mul_ps (mx, my));
        d -= 8;
    }

    __m128 msum2 = _mm256_extractf128_ps(msum1, 1);
    msum2 +=       _mm256_extractf128_ps(msum1, 0);

    if (d >= 4) {
        __m128 mx = _mm_loadu_ps (x); x += 4;
        __m128 my = _mm_loadu_ps (y); y += 4;
        msum2 = _mm_add_ps (msum2, _mm_mul_ps (mx, my));
        d -= 4;
    }

    if (d > 0) {
        __m128 mx = masked_read (d, x);
        __m128 my = masked_read (d, y);
        msum2 = _mm_add_ps (msum2, _mm_mul_ps (mx, my));
    }

    msum2 = _mm_hadd_ps (msum2, msum2);
    msum2 = _mm_hadd_ps (msum2, msum2);
    return  _mm_cvtss_f32 (msum2);
}