http://d.puremagic.com/issues/show_bug.cgi?id=4717
Don <clugd...@yahoo.com.au> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |clugd...@yahoo.com.au --- Comment #2 from Don <clugd...@yahoo.com.au> 2010-08-24 00:33:44 PDT --- (In reply to comment #0) > - The count() is also known known as Population or Hamming weight. This is > useful for Hamming distances, to count bits in many situations, like for > example for the Sieve of Eratosthenes. There are ways and refined algorithms > to > speed up this operation a lot. And this is a very commonly useful operation. I > may offer some D code if you want. See also: > http://en.wikipedia.org/wiki/Hamming_weight > http://graphics.stanford.edu/~seander/bithacks.html > And see also the __builtin_popcount() built-in function of GCC. Curious fact: the built-in popcount instruction isn't much use for bit arrays. It's great for 64 bit longs (especially for chess programs!) but once you have a dozen machine words or more, it's faster to add the bits sideways. An interesting consequence of this is that Intel/AMD's new popcount instruction is hardly ever useful... -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------