mureva opened a new issue, #21195:
URL: https://github.com/apache/mxnet/issues/21195
I have an observation and I'm hoping someone can advise.
I have a scenario where I maintain a large table of vectors, so a basic
(n,m) array of n vectors of size m. I then have some system that generates
indices into this table, and I want to pull rows out of the table at those
indices. (more background? A hash table version of NeRF is what we're making).
So, I have a set of indices, and I want to gather the rows out of the table
to make use of elsewhere. There's two operators in mxnet that will do the job -
`gather_nd` and `take`
I could have more than 100k, even 1000k indices:
- at 100k `take` will do a forward pass in less than 1 ms, but a backward
pass will take about 45 ms. Meanwhile, `gather_nd` will do a forward pass in
about 16 ms, and a backward pass in under 1 ms.
- At 1000k indices, `take` is 4 ms fwd, 400 ms bwd, gather is 170 ms fwd,
1ms bwd. .
So... obvious question... is there a way to get the best of both worlds
here? The fast forward pass of `take`, the fast backward pass of `gather_nd`?
Is there a better operator for gathering rows from the table?
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