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joschu / cgt

Computation Graph Toolkit

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Negative step when slicing

joschu opened this issue · comments

commented

Currently you can't do x[::-1] or x[:,::-1]. Currently x[start:stop:step] produces a GetSli Op with those arguments, however some of the logic assumes that step is positive. We have two choices

  1. generalize GetSli to work with negative step
  2. assume that if a symbolic value for step is provided, it's positive. If it's negative at runtime, throw an exception. If it's non-symbolic and negative, use a Flip Op.
commented

oops, somehow issue got created twice