On Fri, Jun 1, 2018 at 9:46 AM, Chris Barker <chris.barker@noaa.gov> wrote:
numpy is also quite a bit slower than raw python for math with (very) small arrays:
doing a bit more experimentation, the advantage is with pure python for over 10 elements (I got bored...). but I noticed that the time for numpy computation is pretty much constant for 2 up to around 100 elements. Which implies that the bulk of the issue is with "startup" costs, rather than fancy indexing or anything like that. so maybe a short cut wouldn't be helpful. Note if you use a list comp (the pythonic translation of an array operation) thecrossover point is about 15 elements (in my tests, on my machine...) In [90]: % timeit t2 = [x * 10 for x in t] 920 ns ± 4.88 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each) -CHB
In [31]: % timeit t2 = (t[0] * 10, t[1] * 10) 162 ns ± 0.79 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
In [32]: a Out[32]: array([ 3.4, 5.6])
In [33]: % timeit a2 = a * 10 941 ns ± 7.95 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)
(I often want to so this sort of thing, not for performance, but for ease of computation -- say you have 2 or three coordinates that represent a point -- it's really nice to be able to scale or shift with array operations, rather than all that indexing -- but it is pretty slo with numpy.
I've wondered if numpy could be optimized for small 1D arrays, and maybe even 2d arrays with a small fixed second dimension (N x 2, N x 3), by special-casing / short-cutting those cases.
It would require some careful profiling to see if it would help, but it sure seems possible.
And maybe scalars could be fit into the same system.
-CHB
--
Christopher Barker, Ph.D. Oceanographer
Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker@noaa.gov
-- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov