lerp is currently only dispatched for float and double as seen here 9. I don’t know, if half would not yield stable results or if there are other limitations.
Maybe @ngimel knows the reason.
As a workaround, you could transform your data back to a FloatTensor, apply lerp, and transform it back, if you are using a manual approach. If you are using torch.cuda.amp, you could disable autocast for this particular operation.