30 Dec
2009
30 Dec
'09
5:42 a.m.
Am Dienstag 29 Dezember 2009 20:16:59 schrieb Daniel Fischer:
especially the claim that going by primes squares is "a pleasing but minor optimization",
Which it is not. It is a major optimisation. It reduces the algorithmic complexity *and* reduces the constant factors significantly.
D'oh! Thinko while computing sum (takeWhile (<= n) primes) without paper. It doesn't change the complexity, and the constant factors are reduced far less than I thought. The huge performance differences I had must have been due to cache misses (unless you use a segmented sieve, starting at the square reduces the number of cache misses significantly).