Author: Volker Böhm
Date: 07:15:42 03/29/04
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On March 29, 2004 at 09:27:52, Zheng Zhixian wrote: >Peter Berger wrote in a thread below > >"Usually programs assume the second move of the PV as being played, and then >think as if it were their own move in the meantime. If the expected move gets >played indeed, some (loads of at times ) time has been saved - else the time is >lost (despite some potentially useful entries in the hashtable). > >Another approach ( inferior) is to just think as if you were the opponent during >ponder and rely on savings from the hashtable you achieved -you get some useful >entries in the hashtable anyway, but this can't be an optimal strategy IMHO." > >I gather from various responses that the first approach is better if you can >correctly guess the right response more than 50% of the time. Could someone >explain why? > >Are there other pondering methods besides these 2? 1-st is easier to implement. Just play guessed move and start searching. If opponent plays guessed move -> continue search until time reached else stop search. 2-nd has nearly the same effect, but less effective. Only one move is searched with a broad alpha/beta window. If the opponent plays this move you could select the answer from the primary variant. But how to continue search? If you restart the search with the opponent move played you can use hash values, but other values are lost or not accurate (killers, history, ...). Thus 1-st plan is better. All other moves (not the one searched first) are searched with a narrowed alpha/beta, expecially when using PVS. If the opponent plays not the first move, you have nearly nothing left from your search, even no best answer as it failed low (wasn´t the best move). Other idea (i´ve implemented this in a game of connect-four): If your time control gives an average of 1 min. per search an your opponent searches for 3 minutes, you can calculate answers for 3 different possible moves, with 1 minute per search. Improvements (haven´t tried those jet) -Search with narrowed aspiration window: -If your search fails high on the aspiration window you can search another guess, storing your fail high move. -If it fails low you stay on this move. Greetings Volker
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