Vincent Davis wrote:
Out of pure curiosity I would like to compare the efficiency of different
methods of finding primes (need not be consecutive). Let me be clear, given
2min, how many primes can you find, they need not be in order or
consecutive. I have not seen any examples of this. I am assume the solution
is different depending on the time give, 2min or 2 hours. I assume a sieve
solution would be best for larger times. When the numbers get really large
checking to see if they are a prime gets costly.
So what do you think?
*Vincent Davis
720-301-3003 *
vinc...@vincentdavis.net
my blog <http://vincentdavis.net> |
LinkedIn<http://www.linkedin.com/in/vincentdavis>
The sieve can be very efficiently written, but you have to decide
whether to optimize for memory size or for speed. At a minimum for size
you need an object for each prime currently found, and you will be
looking through that list for each new candidate. Incidentally this
approach can be done without any division. If you have memory to burn,
you make a bit array equal in size to the largest prime you expect to
encounter.
There are also good algorithms for deciding whether a number of a
particular form is prime. For example, there's a test for numbers of
the form 2**n + 1.
And don't forget the Miller-Rabin test.
DaveA
--
http://mail.python.org/mailman/listinfo/python-list
