[Python-Dev] genexps slow? (original) (raw)
jiwon jiwon at softwise.co.kr
Wed Mar 31 02:41:43 EST 2004
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[Tim] > Make r a lot bigger, and I > expect > the genexp will get relatively faster (due to better cache behavior).
[Raymond ]
Also, try a timing with "sum(x for x in xrange(100000))". This will highlight the differences in behavior. With xrange, this genexp will be able to execute entirely in cache.
I just tried timing it. For your information, here're results. :)
[jiwon at holmes] ./python ./Lib/timeit.py -s 'r=range(10000000)' 'sum(x for x in r)' 10 loops, best of 3: 4.83 sec per loop [jiwon at holmes] ./python ./Lib/timeit.py -s 'r=range(10000000)' 'sum([x for x in r])' 10 loops, best of 3: 6.49 sec per loop [jiwon at holmes] ./python ./Lib/timeit.py 'sum(x for x in xrange(10000000))' 10 loops, best of 3: 5.14 sec per loop [jiwon at holmes] ./python ./Lib/timeit.py 'sum([x for x in xrange(10000000)])' 10 loops, best of 3: 5.85 sec per loop
Tried with lazy-binding version of genexpr, and non-optimized version of listcomp.
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