Debugging reason for python running unreasonably slow when adding numbers
Edmondo Giovannozzi
edmondo.giovannozzi at gmail.com
Mon Mar 20 11:21:12 EDT 2023
> > def sum1():
> > s = 0
> > for i in range(1000000):
> > s += i
> > return s
> >
> > def sum2():
> > return sum(range(1000000))
> Here you already have the numbers you want to add.
Actually using numpy you'll be much faster in this case:
§ import numpy as np
§ def sum3():
§ return np.arange(1_000_000, dtype=np.int64).sum()
On my computer sum1 takes 44 ms, while the numpy version just 2.6 ms
One problem is that sum2 gives the wrong result. This is why I used np.arange with dtype=np.int64.
sum2 evidently doesn't uses the python "big integers" e restrict the result to 32 bits.
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