On Jan 31, 10:53 am, Mensanator <mensana...@aol.com> wrote:
> On Jan 31, 8:05 am, Mark Dickinson <dicki...@gmail.com> wrote:
>
> > On Jan 31, 1:23 pm, Steve Holden <st...@holdenweb.com> wrote:
>
> > > Much more significant points, given the limited precision of the doubles
> > > Python will be using. Could gmpy do this better, I wonder?
>
> > Almost certainly, if exact results are wanted! At least, GMP has
> > an mpz_root function; I don't know offhand whether gmpy makes it
> > accessible from Python.
>
> > Mark
>
> What am I doing wrong here?
>
> IDLE 2.6b1
>
> >>> import timeit
> >>> from gmpy import root
> >>> root(4021503534212915433093809093996098953996019232,13)
> (mpz(3221), 0)
> >>> t1 = timeit.Timer("x = root(a,r)", "a =
> >>> 4021503534212915433093809093996098953996019232; r = 13")
> >>> t1.timeit()
>
> Traceback (most recent call last):
> File "<pyshell#5>", line 1, in <module>
> t1.timeit()
> File "C:\Python26\lib\timeit.py", line 193, in timeit
> timing = self.inner(it, self.timer)
> File "<timeit-src>", line 6, in inner
> NameError: global name 'root' is not defined
Never mind, I figured it out.
>>> import gmpy
>>> a=gmpy.mpz(4021503534212915433093809093996098953996019232)
>>> r=13
>>> t1 = timeit.Timer("x = root(a,r)", "from gmpy import root; from __main__
>>> import a,r")
>>> t1.timeit()
4.7018698921850728
For comparison:
>>> t2 = timeit.Timer("x = n**power", "n =
>>> 4021503534212915433093809093996098953996019232.; power = 1./13")
>>> t2.timeit()
0.43993394115364026
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