Re: The hardest Euler problem

On May 4, 2:13 am, m...@[EMAIL PROTECTED]
 (Marcel Hendrix) wrote:
> cac <c...@[EMAIL PROTECTED]
> writes Re: The hardest Euler problem
> [..]
>
> >> Someone posted this PARI/GP solution to problem 12:
> >> n=0; until(numdiv(n*(n+1)/2) > 500, n++); n*(n+1)/2
> >> He said it took about 50ms on his Intel 2.52GHz.
>
> What else to expect with a built-in number-of-divisors function?

What else?  We expect the Forth version to live up to
Jeff Fox's boast that rewriting a program in Forth
makes it 100 times smaller and 1000 times faster.

>
> > Sigh. My solution takes 1h45m. I think maybe PARI/GP knows things
about
> > factoring that I don't.
>
> What you can easily see is that one only needs to count to below the
> square root of u1, because each successful division delivers you two
> valid divisors. If you take that into account, you solve the problem
> in 800 ms

If you take more than that into account and use Pascal,
you solve the problem in 109 ms.