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NVIDIA / MinkowskiEngine

Minkowski Engine is an auto-diff neural network library for high-dimensional sparse tensors
https://nvidia.github.io/MinkowskiEngine
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Is it possible to calculate the second derivatives of sparse tensor operations? #242

Open wisclmy0611 opened 3 years ago

wisclmy0611 commented 3 years ago

Hi Choy. Thanks for your great work on this project! I'm trying to calculate the second derivatives of sparse tensor operations (e.g. sparse convolution). I found that the backward operation of sparse convolution doesn't itself have a backward operation, which makes it impossible to calculate the second derivative. Are there some quick hacks I can use to calculate it then? For example, if the current C++/CUDA code can be reused, I could write a backward function that itself has a backward function calling into the existing C++/CUDA code.

https://github.com/NVIDIA/MinkowskiEngine/blob/21f3930d8bb7d27e844b21aeaf7c1a444576d853/MinkowskiEngine/MinkowskiConvolution.py#L38-L111

chrischoy commented 3 years ago

Unfortunately, it currently doesn't support it, but it would be great if you could make a PR for this!