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Subject: fast bit counting

Author: Flemming Rodler

Date: 19:44:25 04/18/00

Hi,

I am trying to implement a bitboard based chess program on a Pentium or AMD
computer. I need to be able to find the following information fast:

1) The position of the first and/or last bit in a sequence of 64 bits.
2) Count the number of bits that are 1 in a sequence of 64 bits.

I know there is a method that works linear in the number of on-bits for
problem 2:

    for(count = 0; bitboard; count++, bitboard &= (bitboard -1));


Is there anything faster, ie. such lookuptables or machine code intrutions?

What about problem 1?

Thanks in advance for any reply
Flemming

Re: fast bit counting Ernst A. Heinz 08:02:52 04/19/00
- Bitcount explained Oliver Roese 19:04:54 04/19/00
  - Re: Bitcount explained Bo Persson 05:48:14 04/21/00
    - Re: Bitcount explained Oliver Roese 03:23:50 04/24/00
      - Re: Bitcount explained Bo Persson 07:46:17 04/24/00
Re: fast bit counting Brian Richardson 06:52:00 04/19/00
Re: fast bit counting Jeremiah Penery 02:41:00 04/19/00
Re: fast bit counting Steve Maughan 01:02:17 04/19/00
Re: fast bit counting Dan Newman 00:27:16 04/19/00
- Re: fast bit counting Tony Werten 01:31:48 04/19/00
  - Re: fast bit counting Dan Newman 11:13:05 04/19/00
    - Re: fast bit counting Bo Persson 11:21:45 04/19/00
  - Re: fast bit counting Steve Maughan 05:23:48 04/19/00
    - Re: fast bit counting Tony Werten 05:42:12 04/19/00
- Re: fast bit counting Dan Newman 00:37:59 04/19/00
Re: fast bit counting Dann Corbit 20:39:31 04/18/00
- Re: fast bit counting Dan Newman 11:32:33 04/19/00
  - Re: fast bit counting Heiner Marxen 12:01:10 04/19/00
    - Re: fast bit counting Dan Newman 13:24:18 04/19/00
Re: fast bit counting Tom Kerrigan 20:12:32 04/18/00

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