Closed
Description
We should make our slicing and assignment ops more general to capture more of the functionality of numpy slicing, and add __getitem__ sugar for all of it. Specifically,
- We should have a 2.5 dimensional set of ops, with dimensions (1) get vs. set, (2) slice type, and for the assignment ops (3) the update op. Currently we have
slice,assign_update,assign_add,assign_sub,gather,scatter_update,scatter_add,scatter_sub. We should also haveassign_slice_update,assign_slice_add,assign_slice_sub. - Both slicing and slice assignment should support strides, with no performance cost if strides aren't used.
- Ideally, the slice ops should support negative indexing a la Python. Since the slice parameters are already CPU, this is implementable with near zero cost. The unfortunate bit is that since we picked the wrong format for specifying ranges (start + length instead of start : end), negative indexing might be awkward. Thus, it might be best left to a separate bug.
- Support numpy-like boolean indexing.
- Generalize
gatherandscatter_*to take an array of input index tensors, efficiently broadcast them, and do multidimensional indexing similar to numpy. - Make
__getitem__provide sugar for all of the above. Ideally we'd have something idiomatically similar at least to__setitem__, but this is problematic since the returned assignment op is important to have,__setitem__does not return a value, and the nice range sugar is available only inside indexing / assignment calls.
@ebrevdo: I'm assigning this to you for now since you might get to it first, but feel free to grab only the piece of it that you need for now.