Author: Pauli Misikangas
Date: 04:18:47 10/28/98
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On October 27, 1998 at 15:54:25, Peter McKenzie wrote: >On October 27, 1998 at 09:16:59, Mike Stoker wrote: > >>Does anyone know if any of the current chess programs perform incremental >>evaluations of positions. I.e. To evaluate a position after a move is played, >>just consider the changed features of the position. I think a possible way to > >Most programs maintain at least part of their evaluation incrementally, for >example material, and the piece square table based evaluation. For the pawn >structure evaluation, using a separate hash table is even faster than >maintaining the score incrementally. For some other things, incremenatal >evaluation might get pretty complex. In my Shocky (which is mainly a shogi program, but can play also chess, although quite poorly at the moment) I use fully incremental evaluation. During every move, I update only those parts of the evaluation that have changed. So, when the "evaluation function" is called I only sum all evaluation-values (material, attack, ..., see the list below) together. Currently, the evaluation consists of the following parts: - material - attack - defense - board control - piece position - piece movement - castling (not as in chess, pieces around the king) - king safety - hand pieces (in shogi you can drop captured piece back to the board) - piece freedoms (number of safe squares to which pieces can move) - blocked pieces (penalty for pieces that cannot move safely) - plan success (for example, Shocky might have a plan to make a castle) I quess that many of those values would make my evaluation extremely slow if they were calculated each time 'evaluate' is called. With incremental evaluation they can be calculated at a very low cost. PS. I don't use bitboards. - Pauli Misikangas -
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