* update fuser to match ATen-formatted JIT ops
* fix concat optimizations and add test
* allow onnx export to work with single-export functions
* fix onnx handling of multi-return nodes.
* nits, format, vision test update
* fix add constant
* fix driver init issues
* Add missing Neg symbolic.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Approach is based on the approach of THC's pointwiseApply{1,2,3} family of kernels,
but doesn't have any dependencies on that code.
Adjacent contiguous dimensions of input tensors are compressed to reduce the complexity of indexing math.
For the completely contiguous case, the indexing logic simplifies to just the linear index.
In simple tests, this code matched or beat the equivalent from THC.
