[Numpy-discussion] numpy speed question
Thu Nov 25 15:34:24 CST 2010
On Thu, Nov 25, 2010 at 4:13 AM, Jean-Luc Menut <email@example.com> wrote:
> Hello all,
> I have a little question about the speed of numpy vs IDL 7.0. I did a
> very simple little check by computing just a cosine in a loop. I was
> quite surprised to see an order of magnitude of difference between numpy
> and IDL, I would have thought that for such a basic function, the speed
> would be approximatively the same.
> I suppose that some of the difference may come from the default data
> type of 64bits in numpy and 32 bits in IDL. Is there a way to change the
> numpy default data type (without recompiling) ?
> And I'm not an expert at all, maybe there is a better explanation, like
> a better use of the several CPU core by IDL ?
> I'm working with windows 7 64 bits on a core i7.
> any hint is welcome.
> Here the IDL code :
> Julian1 = SYSTIME( /JULIAN , /UTC )
> for j=0,9999 do begin
> for i=0,999 do begin
> Julian2 = SYSTIME( /JULIAN , /UTC )
> print, (Julian2-Julian1)*86400.0
> % Compiled module: $MAIN$.
> The python code:
> from numpy import *
> from time import time
> time1 = time()
> for j in range(10000):
> for i in range(1000):
> time2 = time()
> print time2-time1
> In : run python_test_speed.py
> NumPy-Discussion mailing list
Vectorised numpy version already blow away the results.
Here is what I get using the IDL version (with IDL v7.1):
IDL> .r test_idl
% Compiled module: $MAIN$.
I: time run test_python
and using a Cythonized version:
from math import pi
cdef extern from "math.h":
cpdef float myloop(int n1, int n2, float n3):
cdef float a
cdef int i, j
for j in range(n1):
for i in range(n2):
compiling the setup.py file python setup.py build_ext --inplace
and importing the function into IPython
from mycython import myloop
I: timeit myloop(10000, 1000, 100.0)
1 loops, best of 3: 2.91 s per loop
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