NNUE is a 4 layer (1 input + 3 dense) integer only neural network.

It's just over 82,000 parameters.[1] That's a very shallow, small NN - by comparison something like EfficientNet-B1[2] is 7.8M parameters, and that's considered a small network.

[1] https://www.chessprogramming.org/Stockfish_NNUE#NNUE_Structu...

[2] https://proceedings.mlr.press/v97/tan19a/tan19a.pdf

I am involved in lc0 development and fairly aware of SF dev. NNUE is a very small (3 layer dense) cpu only net.