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Subject: Re: hash entry replacement schemes-fail soft implications and IID

Author: scott farrell

Date: 20:41:55 09/14/02

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Does anyone know what implications fail-soft might have on hashing?

If you do a search say from 1 to 2, and under fail soft it returns 2.5
(fail-high / beta cutoff). I am currently storing the score as a beta cuttoff of
2.5. If I see this position again, and the depth is good enough, I return the
value from the hash table, so this is fail-soft as well.

if (mainTable.flag[te] == flagBeta)
                    if (mainTable.value[te] >= beta)
                                    return mainTable.value[te];

I was tracking IID failures, and came up with some debugging that shows
occaisonally no entry in the hashtable after a score of >= beta. I am still
trying to trace it down. It seems lots more of these occured nearer to the
terminal nodes (search horizon). I stopped IID recursing nearer the terminal
nodes, and many of the failures stopped. I guess I might not be hashing enough
details near the terminal nodes. I have tried turning on and off storing values
from the qsearch, but it didnt seem to effect things.



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