Add TrackedArray support for repeat(x; inner, outer)

[staticfloat]

This makes it really easy to do things like make Upsample layers, which are pretty useful for autoencoders.

[MikeInnes]

This looks good, but it'd be worth considering how we make this work with the GPU eventually. Is there a more broadcast-y way to do this, or do we need an inverse-repeat kernel?

[staticfloat]

Yeah, this is pretty straightforward, so I imagine writing a GPU-friendly kernel wouldn't be too hard; just some index processing.

What does a "more broadcast-y" way mean? I'm not sure how to think about a "broadcasted" kernel in this context, since the index of the input data and the index of the output data are not the same. Additionally, it's not a one-to-one mapping; each input will be written to an output multiple times.

[MikeInnes]

Yeah I just meant using existing GPU-friendly primitives; you can sometimes hack broadcasting to do stuff like this (e.g. kronecker products) but it sounds like that's not really the case here. I'm sure we can figure out the kernel later anyway.

[staticfloat]

I suppose you could write a massively parallel version where you construct a source index from every destination index, then run A[dest_idxs] .= B[src_idxs].

[MikeInnes]

@americast might be worth looking at what this needs to work on the GPU.

@staticfloat thanks for the patch!

[americast]

Sure, will have a look 👍

…

On Wed 6 Jun, 2018, 22:05 Mike J Innes, ***@***.***> wrote: @americast <https://github.com/americast> might be worth looking at what this needs to work on the GPU. @staticfloat <https://github.com/staticfloat> thanks for the patch! — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#270 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AWD4xg5av2fK7fy0UA7ipJi8dMFVoZAiks5t6AS3gaJpZM4UJmMt> .