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Subject: Random keys and hamming distance

Author: James Swafford

Date: 20:26:08 08/16/02

I'm in the process of tracking down some hashing problems, and
I'm starting with my Zobrist keys.  For each piece (i.e. bp, wp,
wr, ...) I have 64 keys.  I have 65 keys for "ep square", two
for "player to move", 16 for castling rights.  All keys are 64 bits.

I just did a test to find the minimum hamming distance among
all keys, and it was 14 bits.  That seems a bit low.

I think the way I'm doing 64 bit random number generation sucks.
Here it is:

Bitmap RandomBitmap(void)
{
   Bitmap r1,r2;

   r1=Random32();
   r2=Random32();

   return ((r1<<32)|r2);
}


Ok, someone please confirm that this sucks and tell me a better
way. :)

I'm also interested in hearing what others are getting for min
hamming distance between keys.

--
James

• Re: Random keys and hamming distance Vincent Diepeveen 07:03:27 08/17/02
• Re: Random keys and hamming distance Gerd Isenberg 04:04:18 08/17/02
  • Re: Random keys and hamming distance Will Singleton 14:01:17 08/17/02
    • Re: Random keys and hamming distance Dieter Buerssner 14:18:19 08/17/02
      • Re: Random keys and hamming distance Vincent Diepeveen 20:11:36 08/17/02
• Re: Random keys and hamming distance Alessandro Damiani 03:48:24 08/17/02
• Re: Random keys and hamming distance Andrew Williams 03:35:16 08/17/02
  • Re: Random keys and hamming distance Dieter Buerssner 14:41:52 08/17/02
    • Re: Random keys and hamming distance Robert Hyatt 20:12:59 08/18/02
    • Re: Random keys and hamming distance Andrew Williams 15:17:08 08/17/02
    • Re: Random keys and hamming distance Dieter Buerssner 15:08:03 08/17/02
• Re: Random keys and hamming distance Steve Maughan 00:57:50 08/17/02
• Re: Random keys and hamming distance Will Singleton 21:51:59 08/16/02
  • Re: Random keys and hamming distance Dieter Buerssner 14:29:58 08/17/02
  • Re: Random keys and hamming distance Daniel Clausen 00:38:04 08/17/02
    • Re: Random keys and hamming distance Dieter Buerssner 13:52:14 08/17/02
  • Re: Random keys and hamming distance Gian-Carlo Pascutto 00:20:19 08/17/02
    • Re: Random keys and hamming distance Ron Murawski 07:03:30 08/17/02
      • Re: Random keys and hamming distance Gian-Carlo Pascutto 01:41:48 08/18/02
        • Re: Random keys and hamming distance Ron Murawski 06:59:23 08/18/02
    • Re: Random keys and hamming distance Sune Fischer 01:08:02 08/17/02
  • Re: Random keys and hamming distance Russell Reagan 22:05:30 08/16/02
    • Re: Random keys and hamming distance Ricardo Gibert 00:29:02 08/17/02
      • Re: Random keys and hamming distance Russell Reagan 06:23:55 08/17/02
• Re: Random keys and hamming distance Russell Reagan 20:48:19 08/16/02
  • Re: Random keys and hamming distance Uri Blass 22:11:13 08/16/02
    • Re: Random keys and hamming distance Russell Reagan 22:16:05 08/16/02
      • Re: Random keys and hamming distance James Swafford 06:20:38 08/17/02
      • Re: Random keys and hamming distance Uri Blass 22:34:19 08/16/02

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