How to implement this custom NN layer (implement the Accumulate function in the layer)?

Question

I will use this function layer to definte a custom LossFunction in the net. How do I construct a NetGraph to implement this function?

Answer 1

The Documentation page for Accumulate provides us with a hint, namely that:

Accumulate is equivalent to a particular case of FoldList:

In[1]:= FoldList[Plus, {a, b, c, d}] == Accumulate[{a, b, c, d}]
Out[1]= True

With this in mind, we turn to the new structural net operators, NetFoldOperator, and in-fact the very first example is this particular case!

core =NetGraph[{Plus}, {{NetPort["Input"], NetPort["State"]} -> 1}];
fold = NetFoldOperator[core];
fold[Range[10]]
Out[30]= {1., 3., 6., 10., 15., 21., 28., 36., 45., 55.}