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ENH: Expose `bit_count` ufunc equivalent to the scalar methods

See original GitHub issue

Modern CPUs have a builtin popcount instruction that counts the number of 1 bit in an unsigned integer. It would be great if numpy has a routine that exposes this operation.

Both GCC and MSVC have builtin functions for this instruction.

Possible usage:

>>> np.popcount(4)
1
>>> np.popcount(np.arange(5, dtype=np.uint))
array([0, 1, 1, 2, 1])

Issue Analytics

State:
Created 3 years ago
Reactions:23
Comments:33 (22 by maintainers)

Top GitHub Comments

5reactions

BartMasseycommented, Jan 7, 2021

Table-driven is probably the best choice for this situation, and this is a nice implementation. Thanks!

That said, still want a popcount primitive. 😃

2reactions

eric-wiesercommented, Jun 27, 2021

Frankly I think we should add both; a new bit_count ufunc, and a np.integer.bit_count() wrapper just to make numpy ints work slightly better where int is expected

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