[Python-Dev] Unicode charmap decoders slow (original) (raw)

Walter Dörwald walter at livinglogic.de
Tue Oct 4 09:37:29 CEST 2005

Am 04.10.2005 um 04:25 schrieb jepler at unpythonic.net:

As the OP suggests, decoding with a codec like mac-roman or iso8859-1 is very slow compared to encoding or decoding with utf-8. Here I'm working with 53k of data instead of 53 megs. (Note: this is a laptop, so it's possible that thermal or battery management features affected these numbers a bit, but by a factor of 3 at most)

$ timeit.py -s "s='a'531024; u=unicode(s)" "u.encode('utf-8')" 1000 loops, best of 3: 591 usec per loop $ timeit.py -s "s='a'531024; u=unicode(s)" "s.decode('utf-8')" 1000 loops, best of 3: 1.25 msec per loop $ timeit.py -s "s='a'531024; u=unicode(s)" "s.decode('mac-roman')" 100 loops, best of 3: 13.5 msec per loop $ timeit.py -s "s='a'531024; u=unicode(s)" "s.decode('iso8859-1')" 100 loops, best of 3: 13.6 msec per loop With utf-8 encoding as the baseline, we have decode('utf-8') 2.1x as long decode('mac-roman') 22.8x as long decode('iso8859-1') 23.0x as long Perhaps this is an area that is ripe for optimization.

For charmap decoding we might be able to use an array (e.g. a tuple
(or an array.array?) of codepoints instead of dictionary.

Or we could implement this array as a C array (i.e. gencodec.py would
generate C code).

Bye, Walter Dörwald

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