I''ve been trying to develop some numerical codes with python, however

got disappointed.

A very simple test,

a = 1.0

for i in range(1000):

for j in range(1000):

a = a+1

unfortunately, it took 4.5 seconds to finish(my machines is fine. P4

3.0G, 1G RAM, it varies according to machine configuration, but should

be in the same level)

for matlab, the same operation took 0.1 seconds,

I use numpy & scipy, they solve the problem most of the times, but

there are cases you can''t avoid loops by vectors. I appreciate the

elegancy of python so much, but I guess I have to gave it up in these

numerical codes.(image processing algorithms), for application

dev/scripting, it''s still my first choice.

A good news is that the same code takes ruby 9.8 seconds.

解决方案At Wednesday 13/12/2006 21:07, Chao wrote:

>I''ve been trying to develop some numerical codes with python, however

got disappointed.

A very simple test,

a = 1.0

for i in range(1000):

for j in range(1000):

a = a+1

unfortunately, it took 4.5 seconds to finish(my machines is fine. P4

3.0G, 1G RAM, it varies according to machine configuration, but should

be in the same level)

How do you measure it? 4.5 secs is far too much. Anyway, try using

xrange instead of range. This is the standard way to do timings:

--- cut ---

def test():

a = 1.0

for i in xrange(1000):

for j in xrange(1000):

a = a+1

if __name__==''__main__'':

from timeit import Timer

t = Timer("test()", "from __main__ import test")

print t.repeat(repeat=3,number=1)

--- cut ---

I got about 0.24 secs with far less hardware.

For vector-oriented operations the NumArray package is well suited.

--

Gabriel Genellina

Softlab SRL

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On Wed, Dec 13, 2006 at 04:07:20PM -0800, Chao wrote:

I''ve been trying to develop some numerical codes with python, however

got disappointed.

A very simple test,

a = 1.0

for i in range(1000):

for j in range(1000):

a = a+1

unfortunately, it took 4.5 seconds to finish(my machines is fine. P4

3.0G, 1G RAM, it varies according to machine configuration, but should

be in the same level)

somethings not right there.

andrew@debian:~

cat pytimetest.py

a=1.0

for i in range (1000):

for j in range (1000):

a=a+1

andrew@debian:~