Fatest standard way to sum bytes (and their squares)?
Hrvoje Niksic
hniksic at xemacs.org
Sun Aug 12 20:50:33 CEST 2007
Erik Max Francis <max at alcyone.com> writes:
> So far the fastest way I've found is using the `sum` builtin and
> generators::
>
> ordinalSum = sum(ord(x) for x in data)
> ordinalSumSquared = sum(ord(x)**2 for x in data)
For ordinalSum, using imap is almost twice as fast:
$ python -m timeit -s 'data=[chr(x) for x in xrange(256)]' 'sum(ord(x) for x in data)'
10000 loops, best of 3: 92.4 usec per loop
$ python -m timeit -s 'data=[chr(x) for x in xrange(256)]; from itertools import imap' 'sum(imap(ord, data))'
10000 loops, best of 3: 55.4 usec per loop
Of course, that optimization doesn't work for the squared sum; using a
lambda only pessimizes it.
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