what does no_residual_list for?

[Lowtec-Sam]

Forward:
if aps[i][1] >= ans[i][0]:
self.no_residual_list.append(i)
Backward:
for triplet-pair in no_residual_list, gradient is set to zeros

Does "aps[i][1] >= ans[i][0]" mean the distance between anchor and positive sample is larger than the distance between anchor and negative sample？ If so, why drop these hard pairs (larger loss pair)?

Another question, u use the sort the positive and negative samples according to the distance between them and anchor, but all these pairs are sent to tripletloss layer, what does this for?