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Subject: Re: Hamming distance code

Author: Larry Griffiths

Date: 13:51:51 02/25/99

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On February 25, 1999 at 15:16:45, Don Dailey wrote:

>Ok, I took a few minutes to look at the problem and it was in
>my hamming distance function.  I was counting the number of
>bits in common, so really my distance function was a closeness
>function!   So the bug was in my code.  It was also the very
>first thing I looked at, since I had a hunch.
>
>I ran your code with my random number generator and it now
>we completely match if I turn off your optimization of taking
>the compliment of good numbers.   That optimization is pretty
>effective and makes it find numbers much more quickly.
>
>It looks like 32 bits is pretty tough to achieve, probably
>not even feasible.  Any idea how to compute the maximum distance
>possible in a given size table of 64 bit numbers?
>
>- Don
>
>
>
>
>
>On February 25, 1999 at 14:15:01, Don Dailey wrote:
>
>>On February 25, 1999 at 08:23:55, Robert Hyatt wrote:
>>
>>>On February 25, 1999 at 00:40:47, Don Dailey wrote:
>>>
Don,

Here is a version of my code that I used to set half of the bits on
in my piece table.  My program ran within 10% timewise using this
code verses random numbers. (The random numbers seemed to work better.)

	unsigned long onebit=0x00000001;
	for(int w=1;w<=bitwidth;w++)
		{
		int	setoncount=384;   // Half the entries in the piecesqtbl
		while(setoncount)
			{
			int p=random(12);
			int sq=random(64);
			if(!(PieceSquareTable[p][sq]&onebit))
				{
				PieceSquareTable[p][sq]|=onebit;
				setoncount--;
				}
			}
		onebit=onebit<<1;
		}


Larry   :-)



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