Author: Robert Hyatt
Date: 07:54:31 03/24/04
Go up one level in this thread
On March 24, 2004 at 07:21:04, Fabien Letouzey wrote: >On March 23, 2004 at 17:17:01, Russell Reagan wrote: > >>On March 23, 2004 at 16:18:24, Robert Hyatt wrote: >> >>>Hashing can cause odd things. >>> >>>For example, you ponder for an abnormally long time and finish (say) a 16 ply >>>search. As you searched position X at ply=1 (not depth = 1 but ply =1...) you >>>get a "fail low" and store (say) score <= XXX, draft=15. >>> >>>Your opponent makes a different move and you start over. When you reach >>>position X, you get a hash hit and you "fail low" because of it, bit when you >>>re-search, you can't use that old fail low hash entry and you are not searching >>>deeply enough to see the 16 ply problem with the move, so you get a screwy >>>score. >>> >>>There is no solution to this... except drop hashing... >> >>To be more precise, you don't have to "drop hashing" completely to avoid this. >>For example, you could still use the hash table only for move ordering and avoid >>the search instability. Of course, it is less effective then. Pick your poison >>:) > >I do exactly that at PV nodes in Fruit, for exactly that reason. >Please stop having exactly the same ideas as I do ;) > >Fabien. That doesn't solve the problem at all. A non-PV move can have a fail-high stored in the table. You fail high on the move then fail low when you can't resolve it...
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