if it is {-1, 1} it is not probably not affine quantization, what would you quantize 0 into?

I am trying to follow the XNOR-Net 6 paper and its variant which quantizes the filter weights W into B such that W approximates aB where a is a real valued scalar. Thus, by the equation (4) in that paper, Bi = +1 if Wi >= 0 and Bi = -1 if Wi < 0.
I am looking at the ATen code, it seems to be that if we want to add the support such binary quantization scheme, we will have to recompile PyTorch locally in order to have the new ATen library takes effect. Is there any way I can do it using the official PyTorch distribution without re-compilation?