Author: Bahram Namjou
Date: 12:29:20 02/19/06
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On February 19, 2006 at 15:14:10, Harald Lüßen wrote: >On February 19, 2006 at 13:59:36, Bahram Namjou wrote: > >>I asked this question before but with no comments so I post it again! >> >>when the ponder is on and chess engine thinks and evaluates a position, all of >>the further evaluations are only based on one predicted move that considered to >>be the opponent best next move however never this predicted move will change >>during "thinking time" no matter this "thinking time" is 5 seconds or 50 >>minutes...can anyone explain this why?...thanks, bn > >I know two ways of pondering. > >When an engine makes a move emg_move1 it is the first move >in the principle variation: eng_move1 opp_move1 eng_move2 opp_move2 ... > >a) The engine now assumes the opponent will play opp_move1. Internally it >makes the move and starts thinking (pondering) about its own answer, >obviously beginning with eng_move2. >pro: when the opponent really plays opp_move1 the engine can answer >immediately or just use the time advantage and the hash Table and the >so far calculated depth. >con: when the opponent makes another move the search has to start >from the begining. This is like 'no ponder' if there is not just >a simple transposition. Off course it has to correct its internal move >on the board. > >b) The engine starts thinking for the opponents move, beginning with >opp_move1. There could be a better move opp_move1a. There is always >a new principle variation and most important there are new entries >in the hash table. >pro: when the opponent makes the move opp_move1a the pv and the >hash table are full with information to answer this move. >If the opponent plays a move opp_move1b chances are good that it was >considered too and there are some infos in the hash table. >With this strategy a huge thinking time can be used better. >con: If the opponent plays move opp_move1 the hash table entries >with the information belonging to this move may have been overwritten >and we lost a half move of depth. > >There are engines for both strategies. >Many experts say strategy a) is better. At least for good engines >which predict the right move anyway. > >Harald Thank you Herald...can you also compare the infinite analysis with pondering and why the best predicted move doesn't change during pondering in many top engines?...regards...bn
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