[Tutor] Can I speed this up?

[Barry Sperling]

As a newbie, I'd like to know why you used a "for" loop in 
isPrimeSmall(n) and a "while" loop in isPrimeBig(n).  Is there a 
performance difference?
Thanks,
	Barry

Dick Moores wrote:

> I'd greatly appreciate some tutors taking a look at my factorIntegers.py 
> at <http://www.rcblue.com/Python/factorIntegers-forWeb.py>. I've worked 
> hard to make it as efficient as possible, but suspect there is more that 
> could be done. Or maybe I'm completely on the wrong track as far as 
> speed is concerned.
> 
> I've made use of the program to compute prime factors for integers in 
> the 5 quintillion range. Please see 
> <http://www.rcblue.com/Python/IntegerFactorsForWeb.txt>
> for some results from the latest revision of factorIntegers.py.
> 
> You'll note that in almost all cases the primes take the longest time to 
> compute (29 minutes and change). But note also the anomalies listed at 
> the top of the script. Is there something I've missed that would 
> eliminate these? Or are these to be expected, given the nature of the 
> prime factors of these integers?
> 
> I also did some computing in the 400 trillion range, and found a bunch 
> of these anomalies. The worst I could find was 42 seconds (primes took 
> 11 seconds):
> 
> 400,000,000,040,471 = 19502713*20509967
> 42 seconds
> 
> 400,000,000,040,507 = 400000000040507 is PRIME
> 11 seconds
> 
> 
> Also, of course, I'd appreciate criticism (or even deserved praise) of 
> anything that catches your wise and experienced eyes.
> 
> BTW the line drawn in isPrime(n) at 4,611,600,000,000,000,000 is for my 
> computer and operating system. Yours may require a different line. See 
> the "large number question" Tutor thread of 9/25 and 9/26.
> 
> Thanks, tutors.
> 
> Dick Moores
> rdm at rcblue.com
> 
> Python 2.3.4, Win XP
> 
> 
> "Few persons have sufficient wisdom to prefer censure, which is useful, 
> to praise which deceives them."
> 
> - Francois De La Rochefoucauld 
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