|Subject:||Primes() step j += 2*i for less work|
|Date:||Sat, 06 Nov 2010 06:38:29 +1100|
|From:||Kevin Ryde <firstname.lastname@example.org>|
In Bit::Vector 7.1 BitVector_Primes(), as an optimization I wonder if the "j" loop could increment by "j += 2*i" instead of "j += i". The even numbers are already cleared by the 0xAAAA initializer are they?, leaving only odd multiples of i needing attention. Not sure if 2*i would risk overflow if bits==2^32-1, or near there, or make more big sizes where it might overflow. Perhaps the loop condition would be j <= bits-2*i before incrementing, with bits-2*i itself not underflowing because i <= sqrt(bits) so bits >= 2*i ... if that sounds right.