[Numpy-discussion] Sum, multiply are slow ?
Thu Jul 12 00:48:55 CDT 2007
very interesting, however, it would be better if you provide exact code.
I didn't use timeit and I have some troubles with the module.
David Cournapeau wrote:
> While profiling some code, I noticed that sum in numpy is kind of
> slow once you use axis argument:
> import numpy as N
> a = N.random.randn(1e5, 30)
> %timeit N.sum(a) #-> 26.8ms
> %timeit N.sum(a, 1) #-> 65.5ms
> %timeit N.sum(a, 0) #-> 141ms
> Now, if I use some tricks, I get:
> %timeit N.sum(a) #-> 26.8 ms
> %timeit N.dot(a, N.ones(a.shape, a.dtype)) #-> 11.3ms
> %timeit N.dot(N.ones((1, a.shape), a.dtype), a) #-> 15.5ms
> I realize that dot uses optimized libraries (atlas in my case) and all,
> but is there any way to improve this situation ?
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