Re: Very Big numbers

Tom Lake wrote:

> "Sidney Cadot" <sidney@[EMAIL PROTECTED]
> wrote in message
> news:c0e3ep$h6j$1@[EMAIL PROTECTED]
> > Gernot Frisch wrote:
> >
> > >>Can it also find all 100% proven Prime Numbers?
> > >
> > >
> > > Yes, it can:
> > >
> > > int is_prime(BIG_NUM num)
> > > {
> > >    for (BIG_NUM i=3 ; i<num; i++)
> > >       if (!(test_num%i) return 0;
> > >    return 1;
> > > }
> > >
> > > Muahaha! You didn't say anything about speed, did you :)
>
> You should only have to have the loop go up to the square root of num,
not
> all the way to num to test for prime.  That cuts down the time a bit.
>
> Tom Lake
>
> --
> Capaci Occasio

hmmm   forgot about that -- limit approximation of the square root

(square root of a 100 digit number must be fun just by itself....)


approx is  2 ^  half the numbersbit size + 1     (not + 1 if even???)