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Subject: Re: HashTable upper_bound worthless ?

Author: José Carlos

Date: 03:13:46 02/15/01

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On February 14, 2001 at 22:09:24, Larry Griffiths wrote:

>On February 14, 2001 at 14:06:03, José Carlos wrote:
>
>>On February 14, 2001 at 12:37:52, Larry Griffiths wrote:
>>
>>>On February 14, 2001 at 10:11:53, Carmelo Calzerano wrote:
>>>
>>>>On February 14, 2001 at 09:35:58, Larry Griffiths wrote:
>>>>
>>>>>Carmelo,
>>>>>
>>>>>I will dink around with the hash table some more and see if I can find a bug
>>>>>somewhere.
>>>>>
>>>>>Is this Fine 70?
>>>>>
>>>>>[D]8/k7/3p4/p2P1p2/P2P1P2/8/8/K7 w - -
>>>>
>>>>Exactly ;-)
>>>>
>>>>Bye,
>>>>Carmelo
>>>
>>>Ok Carmelo,
>>>
>>>I did find a bug in my hash code and am getting upper_bound cutoffs now.
>>>I owe you one since I was about to give up on the hash table for a while.
>>>I ran the Fine 70 position using a 16meg hash table.  My hash tables are
>>>28 bytes in size.
>>>
>>>My program goes 17 plys in 18 seconds without the hash table,
>>>and 19 plys in 6 seconds with the hash table.
>>>
>>>I noticed that Hardly any of the 16meg hash table was used.  I am only using 1
>>>slot per hash key, and maybe if I add/look at the next 8 slots I can get some
>>>more entries in the hash table and go deeper on plys.
>>
>>  I don't know what you mean with the slots thing (though I figure), but I think
>>you may have a problem with the hash codes, because you're doing too slow in
>>this problem, and don't even fill 1 Mb of the hash...
>>
>>  I may be wrong, but I think your hash codes are not different enough for
>>similar positions.
>>
>>  José C.
>>
>
>Thanks for the information Jose.  I generated my piece-square tables using
>random numbers and the hash-keys in the tables might not be different enough.
>I am using 64-bit hash-keys as 32-bit hash keys were producing lots of instances
>where different positions equated to the same hash-key.  I think this caused my
>program to make some terrible moves so that is why I went to 64-bit hash-keys.
>I will try using some different hash-key generations schemes and then see what
>percentage of the hash-tables is used.
>
>Larry.

  I suggest you trying Crafty's random numbers. I asked Bob's permission and now
use them in my program. And it works just fine.

  José C.



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