Author: Inmann Werner
Date: 01:43:06 12/01/99
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On December 01, 1999 at 04:27:03, Jeremiah Penery wrote: >On December 01, 1999 at 02:50:01, Inmann Werner wrote: > >>On November 30, 1999 at 20:04:00, Gerrit Reubold wrote: >> >>>Two Months (?) ago we had a thread "what should we store if all moves fails >>>low?" with the answer: Nothing! There should be a saving of a few percent of >>>treesize if you don't store "random" moves in the HT. Maybe this could be an >>>improvement of your algorithm? > >>Why stuff in nothing at fail low? >>fail low is bad for move ordering, so I do not use it there. Ok. >>But for normal hashing, I use fail low, if the value<alpha. At mate values, I >>give back something like mate in 500....(brings my prog to sometimes not show >>right "mate in #", bothers me not much) >>I overwrite fail low values first, cause they are the "less value" entrys. >>Why should I search all moves, only to recognize, that it again is a fail low? >>I see nothing good in it. > >The idea is that when you have a fail-high node, ALL of the next-ply moves have >failed low. In this case, you should store nothing in the hash table, because >you don't have a good move to store. If you do store a move here, it's as good >as storing a random move, because any of those moves can turn out to be the >WORST move. They all failed low, and here the algorithm will not tell us which >one is the best; they must be re-searched. Storing a move here will hurt move >ordering, because you keep getting hash-table hits that tell you to search this >move first, even if it turns out to be the worst move. Some misunderstanding maybe... I have a flag in the hash, if the entry was fail low or fail high. I never use a fail low move for move ordering!!! The only info I use is, that the move failed low and the evaluation value it got. If the search window alpha-beta is not open enough, the move will fail low again. Why search again? Also, if the value gives something like mate in n, i use it as mate in 500-n. The PV leads to a mate, why not use the information.... Werner
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