Author: Will Singleton
Date: 14:01:17 08/17/02
Go up one level in this thread
On August 17, 2002 at 07:04:18, Gerd Isenberg wrote:
>On August 16, 2002 at 23:26:08, James Swafford wrote:
>
>>
>>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
>
>I also get a min hamming distance of 14 with this shift left 32. The average
>hamming distance is 31. IMHO it's fine.
>
Did you test for randomness also? In my tests, combining 2 32-bit ints results
in a pretty severe bunching of numbers. I did a graphical look at all the
generated numbers (just stuck them on Excel), and the difference was startling.
Will
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