Re^2: Number functions I have lying around

And you can profit of an enhencemt if you too add if($i%2==0){next} before eleborating the square root, as you can see in the ch_opt row.

          Rate     la     di     ch ch_opt
la     0.329/s     --   -99%   -99%   -99%
di      25.3/s  7600%     --   -50%   -56%
ch      50.4/s 15230%    99%     --   -12%
ch_opt  57.6/s 17417%   127%    14%     --
[download]

There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

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Re^3: Number functions I have lying around by Anonymous Monk on Apr 02, 2015 at 16:39 UTC
A modest improvement in speed may be obtained if one implements the wheel. For example (the modulus is relatively cheap in perl): `sub primes { my $n = shift; return if $n < 2; my @primes = (2); I: for my $i (3 .. $n) { next unless 0x208a28aa & (1 << $i % 30); my $sqrt = int sqrt $i; for my $p (@primes) { next I unless $i % $p; last if $p > $sqrt; } push @primes, $i; } return @primes }` [download]	[reply] [d/l]
Re^4: Number functions I have lying around by Anonymous Monk on Apr 02, 2015 at 16:55 UTC
Actually, it's 0x208a2882, but you have to initialize primes to (2, 3, 5) then..	[reply]