I am trying to use caffe to implement triplet loss described in Schroff, Kalenichenko and Philbin "FaceNet: A Unified Embedding for Face Recognition and Clustering", 2015.
I am new to this so how to calculate the gradient in back propagation?
I assume you define the loss layer as
layer {
name: "tripletLoss"
type: "TripletLoss"
bottom: "anchor"
bottom: "positive"
bottom: "negative"
...
}
Now you need to compute a gradient w.r.t each of the "bottom"s.
The loss is given by:
The gradient w.r.t the "anchor" input (fa
):
The gradient w.r.t the "positive" input (fp
):
The gradient w.r.t the "negative" input (fn
):
The original calculation (I leave here for sentimental reasons...)
Please see comment correcting the last term.
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