[SciPy-dev] unexpectedly slow norm()
Nathan Bell
wnbell@gmail....
Wed Mar 19 02:22:25 CDT 2008
I use norm() frequently in my own codes and I was recently surprised
to see it near the top of my profiling results. It seems that both
SciPy and NumPy incur a large amount of overhead in this operation.
Consider the following script
=================================
from time import clock
from numpy import inner, sqrt, ones
import numpy.linalg
import scipy.linalg
from scipy.lib.blas import get_blas_funcs
x = ones(5*1000*1000)
scipy_norm = scipy.linalg.norm
numpy_norm = numpy.linalg.norm
def adhoc_norm(x):
return sqrt(inner(x,x))
blas_norm = get_blas_funcs(('nrm2',),(x,))[0]
for fn in [scipy_norm, numpy_norm, adhoc_norm, blas_norm ]:
start = clock()
for i in range(10):
n = fn(x)
end = clock()
print "%f seconds per call" % ((end - start)/10.0)
=================================
Which outputs the following on my laptop:
0.407000 seconds per call
0.089000 seconds per call
0.013000 seconds per call
0.012000 seconds per call
--
Nathan Bell wnbell@gmail.com
http://graphics.cs.uiuc.edu/~wnbell/
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