[Numpy-discussion] slow numpy.clip ?
David Cournapeau
david at ar.media.kyoto-u.ac.jp
Mon Dec 18 03:45:09 EST 2006
Stefan van der Walt wrote:
> Hi David
>
> The benchmark below isn't quite correct. In clip2_bench the data is
> effectively only clipped once. I attach a slightly modified version,
> for which the benchmark results look like this:
Yes, I of course mistyped the < and the copy. But the function is still
moderately faster on my workstation:
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.003 0.003 3.944 3.944 slowclip.py:10(bench_clip)
1 0.011 0.011 2.001 2.001 slowclip.py:16(clip1_bench)
10 1.990 0.199 1.990 0.199
/home/david/local/lib/python2.4/site-packages/numpy/core/fromnumeric.py:372(clip)
1 1.682 1.682 1.682 1.682 slowclip.py:19(clip2_bench)
1 0.258 0.258 0.258 0.258
slowclip.py:6(generate_data_2d)
0 0.000 0.000 profile:0(profiler)
I agree this is not really much a difference, though. The question is
then, in the context of matplotlib, is there really a need to copy ?
Because if I do not copy the array before clipping, then the function is
really faster (for those wondering, this is one bottleneck when calling
matplotlib.imshow, used in specgram and so on),
cheers,
David
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