[TOPI] Fast mode in take op

Currently topi.take supports two modes, “clip” and “wrap”, following the numpy take convention (https://docs.scipy.org/doc/numpy/reference/generated/numpy.take.html). However, the clipping operation makes the take op 30% slower when the input shape is sufficiently large, for example with input shape [20, 1500] and indices shape [750]. I would like to propose add a “fast” mode, similar to the numpy “raise” mode, with no clipping, wrapping, or raising error when the indices are out of range. The user will be responsible to make sure the indices are in range.

cc @ajtulloch, @antinucleon

[antinucleon]

I agree that adding assert stmt may also slow down the op. I think it’s okay to add “fast” mode in take and add warning in the doc.

How about adding a compile time warning as well?

[hlu1]

LOG(WARNING) should do. Please review https://github.com/dmlc/tvm/pull/3325