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Subject: Re: Hash tables vs alpha/beta

Author: José Carlos

Date: 14:04:05 01/17/00

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On January 17, 2000 at 16:31:50, Peter Fendrich wrote:

>On January 17, 2000 at 10:49:05, Vincent Diepeveen wrote:
>
>>On January 17, 2000 at 10:23:13, Peter Fendrich wrote:
>>
>>>When searching the hash table, I've detected basicly 9 different states.
>>>The value from the table is a Lower (L) or Upper (U) bound or Inside (I) it's
>>>A/B-window.
>>>For each of these we have 3 cases:
>>>1. value <= current Alpha
>>>2. value >= current Beta
>>>3. current Alpha < value < current Beta
>>>
>>>Combining it all we have: 1L, 1U, 1I, 2L, 2U, 2I, 3L, 3U and 3I
>>>
>>>For now I'm interested in case  and 3U.
>>>When we have 3L, we know that the table entry is the lowest
>>>possible value and that the current Alpha is lower. To me it seems
>>>reasonable to set current Alpha = table value.
>>>For 3L this will be: current Beta = table value.
>>
>>Oh i hear a lot of dudes inventing this. It never worked for me.
>>I don't do it in DIEP. There are more difficult ways to ask for
>>trouble...
>>
>>>That doesn't work well with my program which has a PVS-based alg.
>>
>>right. simple insight will provide us also why.
>>
>>suppose your bound from hashtable is n ply search based. Now you
>>search at ply = n-i ply where i > 0.
>
>I don't follow you here, what's i? depth?

  What he means is that the value from hash table comes from a deeper search (i
is the difference, so i>0), so the current search is unable to find something
that is "hidden" in the hash table value.

  José C.

>
>>
>>Probably more reasons are there than this...
>
>//Peter



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