Speedup when threshold < 1

[SamGG]

Hi,
I read the following code and I am wondering about the following proposal.

FlowSOM/src/som.c

Lines 120 to 141 in 1e5650e

	nearest = 0;
	/* calculate distances in x and y spaces, and keep track of the
	nearest code */
	for (cd = 0; cd < ncodes; cd++) {
	xdists[cd] = distf(&data[i], &codes[cd], px, n, ncodes);
	if (xdists[cd] < xdists[nearest]) nearest = cd;
	}
	if (threshold < 1.0) threshold = 0.5;
	alpha = alphas[0] - (alphas[0] - alphas[1]) * (double)k/(double)niter;
	for (cd = 0; cd < ncodes; cd++) {
	if(nhbrdist[cd + ncodes*nearest] > threshold) continue;
	for(j = 0; j < px; j++) {
	tmp = data[i + j*n] - codes[cd + j*ncodes];
	change += fabs(tmp);
	codes[cd + j*ncodes] += tmp * alpha;
	}
	}
	threshold -= thresholdStep;

When threshold reaches 1, only the best matching unit is updated. The loop L131-L139 looking for the nearest units below the threshold is useless. Only the calculation of the inner loop L134-L138 is needed with cd being nearest. The code at L128 is a weird shortcut IMHO. With the default parameters (grid xdim = ydim = 10, radius is 6), the gain applies in the last 2 loops out of 10 (rlen = 10).
Let me know if there is something I misunderstood.