int
drid_moments(float* coords, int32_t index, int32_t* partners, int32_t n_partners, double* moments)
{
int32_t i;
float d;
moments_t onlinemoments;
__m128 x, y, r, r2, s;
moments_clear(&onlinemoments);
x = load_float3(&coords[3 * index]);
for (i = 0; i < n_partners; i++) {
y = load_float3(&coords[3 * partners[i]]);
r = _mm_sub_ps(x, y); /* x - y */
r2 = _mm_mul_ps(r, r); /* (x - y)**2 */
/* horizontal add the components of d2 with */
/* two instructions. note: it's critical */
/* here that the last entry of x1 and x2 was 0 */
/* so that d2.w = 0 */
s = _mm_add_ps(r2, _mm_movehl_ps(r2, r2));
s = _mm_add_ss(s, _mm_shuffle_ps(s, s, 1));
/* store into a regular float. I tried using _mm_rsqrt_ps, but it's not
accurate to pass the tests */
_mm_store_ss(&d, s);
moments_push(&onlinemoments, 1.0 / sqrt((double) d));
}
moments[0] = moments_mean(&onlinemoments);
moments[1] = sqrt(moments_second(&onlinemoments));
moments[2] = cbrt(moments_third(&onlinemoments));
return 1;
}
/* Initializes moments M for calculating moment MAX_MOMENT and
lower moments. */
static void
init_moments (struct moments *m, enum moment max_moment)
{
assert (m != NULL);
assert (max_moment == MOMENT_MEAN || max_moment == MOMENT_VARIANCE
|| max_moment == MOMENT_SKEWNESS || max_moment == MOMENT_KURTOSIS);
m->max_moment = max_moment;
moments_clear (m);
}