title: Fast Bit Counting
description:


> From: W.Baden (wilbaden@netcom.com)
> Subject: Re: Counting bits...
> Newsgroups: comp.lang.forth
> Date: 1995-02-26 06:12:45 PST

: count-bits    ( number -- bits )
        [ HEX ] DUP  55555555 AND  SWAP  1 RSHIFT  55555555 AND  +
                DUP  33333333 AND  SWAP  2 RSHIFT  33333333 AND  +
                DUP  0F0F0F0F AND  SWAP  4 RSHIFT  0F0F0F0F AND  +
        [ DECIMAL ] 255 MOD
;

> From: Michael Pr"umm (mip@wa.oche.de)
> Subject: Re: bit counting algorithm
> Newsgroups: comp.lang.forth
> Date: 1994-07-28 00:54:03 PST
>
> And here is another one: octal
>

: ones ( uint32 - numbits)
  dup 1 RSHIFT 33333333333 and
  dup 1 RSHIFT 33333333333 and + -
  dup 3 RSHIFT  +  30707070707 and  77 mod
;