I think this is a great idea! I don't see any downsides here. As for the method name, I would lean towards calling it "kind" and using a default value of None for automatic selection, for consistency with np.sort.
On Thu, Jun 16, 2022 at 6:14 AM Sebastian Berg <sebast...@sipsolutions.net> wrote: > Hi all, > > there is a PR to add a faster path to `np.isin`, that uses a look-up- > table for all the elements that are included in the haystack > (`test_elements`): > > https://github.com/numpy/numpy/pull/12065/files > > Such a table means that the memory overhead can be very significant, > but the speedup as well, so there was the idea of adding an option to > pick which version is used. > > The current documentation for this new `method` keyword argument would > be. So the main questions are: > > * Is there any concern about adding such a new kwarg? > * Is `method` the best name? Sorts uses `kind` which may also be good > > There is also the smaller question of what heuristic 'auto' would use, > but that can be tweaked at any time. > > ``` > method : {'auto', 'sort', 'dictionary'}, optional > The algorithm to use. This will not affect the final result, > but will affect the speed. Default is 'auto'. > > - If 'sort', will use a mergesort-based approach. This will have > a memory usage of roughly 6 times the sum of the sizes of > `ar1` and `ar2`, not accounting for size of dtypes. > - If 'dictionary', will use a key-dictionary approach similar > to a counting sort. This is only available for boolean and > integer arrays. This will have a memory usage of the > size of `ar1` plus the max-min value of `ar2`. This tends > to be the faster method if the following formula is true: > `log10(len(ar2)) > (log10(max(ar2)-min(ar2)) - 2.27) / 0.927`, > but may use greater memory. > - If 'auto', will automatically choose the method which is > expected to perform the fastest, using the above > formula. For larger sizes or smaller range, > 'dictionary' is chosen. For larger range or smaller > sizes, 'sort' is chosen.` > ``` > > Cheers, > > Sebastian > _______________________________________________ > NumPy-Discussion mailing list -- numpy-discussion@python.org > To unsubscribe send an email to numpy-discussion-le...@python.org > https://mail.python.org/mailman3/lists/numpy-discussion.python.org/ > Member address: sho...@gmail.com >
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