On Fri, Feb 6, 2009 at 4:19 PM, H.G. le Roy <hgle...@gmail.com> wrote:
> A part of my code deals with the calculation of prime numbers. However it is
> really slow. Hopefully you have some ideas how to make it faster.
>
> pz = [2]
> # only iterate over odd numbers
> for i in xrange(3,2000000,2):
> remprod = 1 # product of remainders
Not sure why you accumulate the products, just keep a flag or use an
else clause on the for loop.
> for j in xrange(len(pz)):
for p in pz:
> remprod *= (i % pz[j])
> if remprod == 0: # if a number is divisible wo remainder its not prime
> break
> if remprod > 0:
> pz.append(i)
You inner loop could be (not tested)
for p in pz:
if i % p == 0:
break
else:
pz.append(i)
You might search the archives for more ideas, this is a popular
question. There is a very slick Python implementation of the Sieve of
Eratosthenes that uses slice assignment to mark off the non-primes.
Kent
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