Joachim Worringen wrote:
> I need to process large lists (in my real application, this is to parse
> the content of a file). I noticed that the performance to access the
> individual list elements degrades over runtime.
>
> This can be reproduced easily using this code:
>
> import time
>
> N=100000
> p=10000
>
> A=[]
> for i in range(N):
> A.append(str(i))
>
> j = 0
> t = time.clock()
> for i in range(len(A)):
> j += int(A[i])
> if i % p == 0:
> t = time.clock() - t
> print t
>
> (the string conversion only servers to increase the duration of each
> iteration; you can observer the same effect with ints, too).
>
> When running this, I get output like this:
> 0.0
> 0.37
> 0.03
> 0.4
> 0.06
> 0.43
> 0.09
> 0.46
> 0.13
> 0.49
>
> I use Python 2.3.4 (#1, Sep 3 2004, 12:08:45)
> [GCC 2.96 20000731 (Red Hat Linux 7.3 2.96-110)] on linux2
>
> I wonder why
> 1. The execution times alternate between "fast" and "slow" (I observe the
> same effect in my much more complex application)
Your timing code is buggy. Change it to
import time
N=100000
p=10000
A=[]
for i in range(N):
A.append(str(i))
j = 0
start = time.clock()
for i in range(len(A)):
j += int(A[i])
if i % p == 0:
end = time.clock()
print end - start
start = end
Does the problem persist? I hope not.
Peter
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