[Tutor] how to handle big numbers

[lina]

On Sat, Dec 10, 2011 at 6:09 PM, Peter Otten <__peter__ at web.de> wrote:
> surya k wrote:
>
>> Finding factorial of 8 or 9 isn't big. If I would like to find factorial
>> of 32327, how can I ?
>
> gmpy is a library designed for working with large numbers. Compare:
>
>>>> import time
>>>> def bench(f, *args):
> ...     start = time.time()
> ...     try:
> ...             return f(*args)
> ...     finally:
> ...             print time.time() - start
> ...
>>>> def fac(n):
> ...     f = 1
> ...     for i in xrange(1, n+1):
> ...             f *= i
> ...     return f
> ...

sorry to interrupt, I tried your example,

$ cat time_func.py
#!/usr/bin/python3

import time

def bench(f, *args):
    start = time.time()
    try:
        return f(*args)
    finally:
        print(time.time() - start)

def fac(n):
    f = 1
    for i in range(1,n+1):
        f *= i
    return f

on idle3

>>> import time_func
>>> time_func.bench(time_func.fac,1000)
0.0015549659729003906
402387260077093773543702433923003985719374864210714632543799910429938512398629020592044208486969404800479988610197196058631666872994808558901323829669944590997424504087073759918823627727188732519779505950995276120874975462497043601418278094646496291056393887437886487337119181045825783647849977012476632889835955735432513185323958463075557409114262417474349347553428646576611667797396668820291207379143853719588249808126867838374559731746136085379534524221586593201928090878297308431392844403281231558611036976801357304216168747609675871348312025478589320767169132448426236131412508780208000261683151027341827977704784635868170164365024153691398281264810213092761244896359928705114964975419909342221566832572080821333186116811553615836546984046708975602900950537616475847728421889679646244945160765353408198901385442487984959953319101723355556602139450399736280750137837615307127761926849034352625200015888535147331611702103968175921510907788019393178114194545257223865541461062892187960223838971476088506276862967146674697562911234082439208160153780889893964518263243671616762179168909779911903754031274622289988005195444414282012187361745992642956581746628302955570299024324153181617210465832036786906117260158783520751516284225540265170483304226143974286933061690897968482590125458327168226458066526769958652682272807075781391858178889652208164348344825993266043367660176999612831860788386150279465955131156552036093988180612138558600301435694527224206344631797460594682573103790084024432438465657245014402821885252470935190620929023136493273497565513958720559654228749774011413346962715422845862377387538230483865688976461927383814900140767310446640259899490222221765904339901886018566526485061799702356193897017860040811889729918311021171229845901641921068884387121855646124960798722908519296819372388642614839657382291123125024186649353143970137428531926649875337218940694281434118520158014123344828015051399694290153483077644569099073152433278288269864602789864321139083506217095002597389863554277196742822248757586765752344220207573630569498825087968928162753848863396909959826280956121450994871701244516461260379029309120889086942028510640182154399457156805941872748998094254742173582401063677404595741785160829230135358081840096996372524230560855903700624271243416909004153690105933983835777939410970027753472000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

>>> time_func.bench(time_func.fac,100)
2.193450927734375e-05
93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000

why the output so long,

Thanks,

>>>> x = bench(fac, 1000)
> 0.00276589393616
>>>> x = bench(fac, 10000)
> 0.247038125992
>>>> x = bench(fac, 30000)
> 1.40305805206
>>>> import gmpy
>>>> x = bench(gmpy.fac, 30000)
> 0.0243360996246
>>>> x = bench(gmpy.fac, 10**6)
> 0.8047311306
>>>> x.numdigits()
> 5565709
>
> http://pypi.python.org/pypi/gmpy
>
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