Thanks! For WebGL, credit goes to https://github.com/waylonflinn/weblas. I only really use GEMM, but it works quite well. In keras.js, convolution is implemented with the oft-used im2col transformation to turn it into a matrix multiply followed by reshape. Convolution kernels directly GLSL could potentially provide speed gains I'm sure, but I can't even imagine writing it for tensors of arbitrary shape.

They mentioned they used the weblas library/module.

See code for example https://github.com/transcranial/keras-js/blob/master/src/Ten... or code on weblas github repo.