Author: William Bryant
Date: 07:18:12 10/19/99
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On October 18, 1999 at 23:12:29, Robert Hyatt wrote: >at times you do a hash probe, and you get a score or bound, but the draft >is insufficient. However, think about your null-move search. It is going >to search this same position, but 2 plies shallower. So if the hash entry >isn't good enough to use normally, remember when you get a UPPER bound from >the hash table, and see if that bound is < the current alpha value. If so, >and the depth is good enough to satisfy the null-move search (draft is at least >remaining depth - 3 plies since null-move will reduce depth by 2 and you would >normally reduce by one more) then you know that the null-move search won't fail >high, since this hash entry says it would fail low. Don't bother trying the >null-move search since you know it won't fail high and will just be wasting >time... > >In crafty, hash.c, the "avoid_null" variable holds this. If we can't fail >high or low or return an exact score, I return this value which says "no >good hash info, but avoid trying null move here anyway..." > >Bob I still think I'm missing something. I understand the explination, but it differs from what is in the source code (I think?). You description say to see if the bound is less than the current _alpha_ value, yet the source compares this to *beta, a pointer to the actual beta. Where I am skipping a beat on this one? Thanks. William wbryant@ix.netcom.com
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