I usually monitor the percentange of correct triplets in each batch. With that I mean the triplets where the distance between the anchor and the negative is bigger than the distance between the anchor and the positive by the margin.
Pytorch triplet loss does not provide tools to monitor that, but you can code it easily as I do in here 109.
I’m the author of the blog post you link Understanding Ranking Loss, Contrastive Loss, Margin Loss, Triplet Loss, Hinge Loss and all those confusing names 165