10000 out kwarg to bincount · Issue #7998 · numpy/numpy · GitHub
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anntzer opened this issue Aug 31, 2016 · 5 comments
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out kwarg to bincount #7998

anntzer opened this issue Aug 31, 2016 · 5 comments

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@anntzer
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anntzer commented Aug 31, 2016

bincount could gain an out kwarg (which would not get zeroed before adding the weights).

Rationale: This would sidestep the issue of poor ufunc.at performance (#5922) at least for the add ufunc.

I'd expect this kwarg to be incompatible with minlength; the minlength would simply be obtained from the length of the out array.
@jaimefrio
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So you would accumulate on top of the value already stored in the array? That's an interesting idea! Can you elaborate on how it replaces .at, maybe with an example?

Deciding on doing this would probably need some discussion on the list, but implementing it should be relatively straightforward.

@anntzer
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anntzer commented Aug 31, 2016

Basically, you'd replace

indices = ...
weights = ...
counts = ... # perhaps a previous value, or just np.zeros(...)
np.add.at(counts, indices, weights)

by

counts = ...
np.bincount(indices, weights, out=counts)

TBH I feel it would be preferable to fix the performance of ufunc.at; OTOH given the discussion on #5922 I guess it's not going to happen any time soon, and this may be a reasonable and simpler to implement workaround.

@seberg
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seberg commented Aug 31, 2016

I think you can get a speedup of maybe even up to 5 without completely overhauling ufunc.at implementation, though.

@mhvk mhvk mentioned this issue Jan 26, 2017
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@mhvk mhvk mentioned this issue Jul 10, 2017
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@huonw huonw mentioned this issue May 13, 2020
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@huonw huonw mentioned this issue May 21, 2020
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@mhvk mhvk mentioned this issue Oct 23, 2022
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@mattip
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mattip commented Feb 1, 2023

In PR #23136 ufunc.add.at became fast enough that I think it can be used for this.

@mattip mattip mentioned this issue Feb 1, 2023
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@mattip
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mattip commented Feb 8, 2023

Closing, #23136 was merged

@mattip mattip closed this as completed Feb 8, 2023
@mattip mattip mentioned this issue Feb 8, 2023
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@seberg @mattip @anntzer @jaimefrio
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