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Subject: Re: Hashing is a complicated affair ?

Author: Andrew Wagner

Date: 15:58:57 04/05/04

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On April 05, 2004 at 18:42:57, rasjid chan wrote:

>On April 05, 2004 at 15:59:40, Dann Corbit wrote:
>
>What fruits! I can't yet digest the apple.
>
>On a more serious note, it seems there MAY BE much more in hashing
>than what I know - UB, LB, EX. I need time to see what all these mean.

UB = Upper bound, LB = Lower bound, EX = exact.

When you store a value in the hash table, sometimes it will not be exact, so you
store some flag along with it that says what kind of position it is. If you just
failed high, all you know is that the score is at least X. If if failed low, all
you know is the score is at most X. And if the score is between alpha and beta,
it's exact.

>
>Rasjid
>
>
>
>>On April 05, 2004 at 15:24:11, rasjid chan wrote:
>>
>>>On April 05, 2004 at 14:44:04, Dann Corbit wrote:
>>>
>>>Maybe you miss my point. Actually I have no references about the
>>>technical "intricacies" about hash table implementation and
>>>I rediscover "new" things about hashing all the time which is BAD.
>>>So I post this to hope someone just confirm with me once if my
>>>analysis could be way wrong!
>>
>>Probably, I cannot answer well about that.
>>
>>I have many kinds of hash table.  One kind scores only exact scores and it is
>>permanent (I save it to disk and restore it from disk).  These are also divided
>>by piece count.
>>
>>The other kind of table stores edge values.  There is only one of these and it
>>is regenerated for every game.
>>
>>I keep as much flag information as possible (this is a null move, a lower bound,
>>an upper bound, unknown, qsearch, EGTB hit, invalid, killer,...)
>>
>>What you describe sounds OK to me.  Since you ask the question, I think you must
>>see some problem.
>>
>>
>>>I did have all the assert()s, you mentioned and I may be the top in using
>>>assert().
>>
>>Have you seen the source code for fruit?



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