`None` Default Arguments about extension-cpp HOT 8 CLOSED

@rusty1s you can now pass None if you use at::optional<at::Tensor> in C++ (and at::nullopt or nullptr as the C++ default type)

from extension-cpp.

Hi, we don't currently provide a way of creating a "void"/"None" Tensor in our C++ extension API. Would it be enough for you to use something like at::empty(torch::CPU(at::kDouble), {0})); as the default argument and then check with .numel() == 0 whether or not it is empty? This would work both in the function prototype and for the py::arg() = ... .

Let me know whether this would be sufficient for you.

from extension-cpp.

Thanks! python setup.py install now works perfectly.

However, calling the function in Python with a None argument gives the following error message:

incompatible function arguments. The following argument types are supported:
1. (tensor1: at::Tensor, tensor2 = tensor([], dtype=torch.float64)) -> at::Tensor

Invoked with: tensor([2, 2]), None

from extension-cpp.

from extension-cpp.

Yeah, I see. Actually, I wanted to pass None, but I guess I'm fine with the proposed solution (unless you know of an easy way to allow for None arguments). Thanks again!

from extension-cpp.

I will keep the possibility of None converting to an undefined Tensor in mind as we expand the extension API. Thanks for posting the issue! I'll mark it as resolved.

from extension-cpp.

@goldsborough how about we expose torch::optional and let Nones bind to that?

from extension-cpp.

Yes that's a good idea, I'll do that

from extension-cpp.