Author: Robert Hyatt
Date: 12:13:59 06/10/98
Go up one level in this thread
On June 10, 1998 at 13:10:23, Carlos Adan Bonilla wrote: >Hi! > >When using a computer to analyze or to play chess, you may find that a >lot of programs have a "Next best move" option in the menu. >As a matter of fact, if you wanna know the second best move in a certain >position alpha-beta pruning is not enough because that second best move >could have been cut off. > >So my first question is: >Do those programs use alpha-beta cut offs? Or do they use an special >version of that algorythm? > >I mean programs which move that second best move immediately after >pushing the "Next best" move... (they don't need to search for it >again). > there are two ways to get this, one is "el cheapo" and the other is "el expensiveo"... "el cheapo" simply stores each PV as the search progresses, and if, on the last iteration, you change your mind one time, you assume the new best move is really the best, which is correct, but you assume the move you changed from is second best, which is baloney. But it does give you a move to claim as "second best"... just that it is wrong. "el expensiveo" requires doing as I do in "annotate" in Crafty. Search all the moves to a fixed depth, taking the best as "best". Remove that move from the ply-1 move list, and search again to the same depth. Take the best move this time as "second best." Remove this move, search again, and you get the third best. And it is *very* costly in terms of time... as you can see... >Second question: when the user selects "Next best" is because he doesn't >like the best move... but the new selected move may have been selected >because it's preparing to move that former best move again but in the >next move (I mean two plies after, the next move of that colour). >But this new line is likely to unsatisfy the user again because it >contains the same rejected move... >How can this things be handled? >Do the existing programs take this into account? >(I don't think so) > >Thx in advance for your answers...
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.