[Tutor] why?

[Kent Johnson]

On Wed, May 28, 2008 at 8:43 PM, Robert William Hanks
<astroultraman at gmail.com> wrote:
>
>  Need ti find out whem a number o this form i**3+j**3+1 is acube.
>  tryed a simple brute force code but, why this not work?
>
> def iscube(n):
>     cubed_root = n**(1/3.0)
>     if round(cubed_root)**3 == n:
>         return True
>     else:
>         return False
>
> for i in range(1,10000000):
>     for j in range(1,10000000):
>          soma= i**3 +j**3 +1
>          if isCube(soma):
>              print i
>              print j
>              print soma

Let's see. The inner loop will run 10000000 * 10000000 =
100000000000000 times. That's a pretty big number. Suppose each
iteration of the loop takes 1 microsecond. (That seems optimistic but
not too much - on my computer iscube(27) takes about 1.3
microseconds.) Then the entire program will complete in 10000000 *
10000000 / 1000000 / 60 / 60 / 24 / 365 = 3 years. Other than that it
look OK to me...

Looks like you need either a better algorithm or a faster computer!

Kent