From: Jimmy Kofler <koflerjim@...>
Date: 2008-04-16T16:36:57+09:00
Subject: Re: Primes in P?

> Posted by Todd Benson (Guest) on 01.04.2008 14:08  
>
>> On Tue, Apr 1, 2008 at 5:19 AM, Todd Benson <caduceass@gmail.com> wrote:
>>
>>
>>  Charles, take a peak at the mathn library for your greatest prime factor...
>>
>>  require 'mathn'
>>  n = 12345654321
>>  p n.prime_division.last[0]
>
> Funny, I tried this with the same number with a 1 attached to the end
> (123456543211).  It took about 20 minutes, but determined it was prime
> (i.e. returned [123456543211, 1]) which means 123456543211 to the
> power of 1.  Coincidence :)
>
> Todd


Well, you could use the Miller-Rabin prime test for a speed up! See:

http://snippets.dzone.com/posts/show/4636

You may check the outcome with primegen, http://cr.yp.to/primegen.html

time -p primes 123456543211 123456543211   # done in well under a second

Cheers,
j. k.


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