Quote from: AstroKev on July 19, 2013, 07:36:58 AM

Quote

I could be wrong, but I'm not convinced this change will make any significant difference. The primorial of 7 is the same as that of 9, since 8 and 9 aren't primes.

No this is not what primorial means.

primorial(1) = 2
primorial(2) = 2 * 3
primorial(3) = 2 * 3 * 5
and so forth.
primorial(7) = 2 * 3 * 5 * 7 * 11 * 13 * 17 = 510510
primorial(9) = 2 * 3 * 5 * 7 * 11 * 13 * 17 * 19 * 23 = 223092870

Notice the list of divisors this produces when using p#9 * some random price
> bc
print 223092870 * 498497689
111211280127377430

http://www.wolframalpha.com/input/?i=factor+%28111211280127377430%29

Honestly I can't say I really understand what the code is doing here, but based on some the comments from Kooooooj and running through gprof, Weave is sucking up all the time -- so I was trying to push some of the work out of there and into the caller function. I am 100% speculating also that the increases in difficulty may make the primorial a little more important. But anyway, mostly just hacking.

oh well, off to bed.

Sorry, I was thinking of this definition, where the primorial of a number is defined as the product of all primes ≤ n.

It seems to be implemented this way in prime.cpp, as the Primorial function stops at the first prime greater than the given number:

Code:

void Primorial(unsigned int p, mpz_class& mpzPrimorial)
{
mpzPrimorial = 1;
BOOST_FOREACH(unsigned int nPrime, vPrimes)
{
if (nPrime > p) break;
mpzPrimorial *= nPrime;
}
}

grc

Posts

Merits