The previous one was slower but now it is faster. How can I make this more consistent? Why cannot I control it?
Where can I find the algorithms implemented under for example pow, /, %, etc.? I could not see them in python documentation? f2(281367918279371279712863756486284619792197836426862028028824908239084023984967328564836783686836834628136791827937127971286375648628461979219783642686202802882490823908402398496732856483678368683683462813679182793712797128637564862846197921978364268620280288249082390840239849673285648367836868368346,9) 8.3809534317e-06 6.70476276809e-06 512 Thanks in advance, 26 Ağustos 2009 13:53 tarihinde Cevahir Demirkıran <cevo...@gmail.com>yazdı: > Thanks for the answer. > Run it with a big number: > > f2(9230821908403878236537264867326482638462035732098490238409328947638257462745672354627356427356742563256745362772537532756732673275732,9) > > I had this result: > > 8.1015883211e-06 > 1.06158743591e-05 > 512 > > 2009/8/26 Mark Tolonen <metolone+gm...@gmail.com<metolone%2bgm...@gmail.com> > > > > >> "Cevahir Demirkiran" <cevo...@gmail.com> wrote in message >> news:3f74e020908251648k7b391a09g78b155507b2f2...@mail.gmail.com... >> >> Hi, >>> >>> I would like to do a floor division by a power of 2 in python to make it >>> faster than / (modular division in 2.x). >>> However, it is slower. >>> What is the reason of that? >>> I checked them via: >>> >>> def f2(x,n): >>> t1 = clock() >>> r = x/pow(2,n) >>> t2 = clock() >>> print (t2-t1) >>> print r >>> t2 = clock() >>> r = x>>n >>> t3 = clock() >>> print (t3-t2) >>> print r >>> >>> >> It's not slower on my system, but note the inconsistent results also: >> >> f2(1024,5) >>>>> >>>> 3.47396033483e-06 >> 32 >> 2.19077375482e-06 >> 32 >> >>> f2(1024,5) >>>>> >>>> 4.84135603429e-06 >> 32 >> 3.08499440393e-06 >> 32 >> >>> f2(1024,5) >>>>> >>>> 4.6782844052e-06 >> 32 >> 3.77604384028e-06 >> 32 >> >> Time it with timeit... >> >> C:\>python -m timeit -n 10000000 -s x=1024 "x>>5" >> 10000000 loops, best of 3: 0.113 usec per loop >> >> C:\>python -m timeit -n 10000000 -s x=1024 "x/pow(2,5)" >> 10000000 loops, best of 3: 0.468 usec per loop >> >> Right-shift is over 4x faster. >> >> -Mark >> >> >> -- >> http://mail.python.org/mailman/listinfo/python-list >> > > > > -- > Cevahir Demirkiran > -- Cevahir Demirkiran
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