[Numpy-discussion] A minor clarification no why count_nonzero is faster for boolean arrays
perimosocordiae at gmail.com
Thu Dec 17 13:37:56 EST 2015
I believe this line is the reason:
On Thu, Dec 17, 2015 at 11:52 AM, Raghav R V <ragvrv at gmail.com> wrote:
> I was just playing with `count_nonzero` and found it to be significantly
> faster for boolean arrays compared to integer arrays
> >>> a = np.random.randint(0, 2, (100, 5))
> >>> a_bool = a.astype(bool)
> >>> %timeit np.sum(a)
> 100000 loops, best of 3: 5.64 µs per loop
> >>> %timeit np.count_nonzero(a)
> 1000000 loops, best of 3: 1.42 us per loop
> >>> %timeit np.count_nonzero(a_bool)
> 1000000 loops, best of 3: 279 ns per loop (but why?)
> I tried looking into the code and dug my way through to this line
> I am unable to dig further.
> I know this is probably a trivial question, but was wondering if anyone
> could provide insight on why this is so?
> NumPy-Discussion mailing list
> NumPy-Discussion at scipy.org
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