Scatter log softmax operation

[mallamanis]

Would you be open for me to contribute a scatter_log_softmax operation in the library? It's a few lines of code using the existing APIs that'd be nice to have in this library, rather than somewhere else.

Adding scatter_logsumexp of #71 would also seem a reasonable step if you're okay with scatter_log_softmax.

[rusty1s]

The main problem with this is that this is not really a scatter_* operation, it just uses scatter_* ops under the hood. I am generally open to it, but we need to distinguish those kinds of ops.

[mallamanis]

Certainly agree that it's not an "primitive" scatter_* operation. It's nevertheless an op that I find myself needing relatively frequently that it'd like to encapsulate in some library to reuse. One suggestion is to put such functions in a pytorch_scatter.composite sub-package.

If pytorch-scatter is or isn't the right place for this, it's up to you as the owner to decide :) Let me know.

[rusty1s]

I like this idea. We can start by adding scatter_softmax and scatter_log_softmax to torch_scatter.composite and adding scatter_logsumexp to the main package.

[mallamanis]

Great! And thanks for your prompt responses. I aim to get some time to work on a PR later today or tomorrow morning.