Author: Robert Hyatt
Date: 20:38:17 01/10/00
Go up one level in this thread
On January 10, 2000 at 21:47:00, Ed Schröder wrote: >On January 10, 2000 at 17:46:22, Bruce Moreland wrote: > >>On January 10, 2000 at 17:32:56, Torstein Hall wrote: >> >>> >>>From the game Shebarkov - Rebel. >>> >>>Why is it so difficult for a program to see a bad bishop? >>> >>>[D] 8/p3kp2/2pr1pb1/2b1p3/P3P1Pp/1PNB1P1P/2K5/3R4 w - - 0 26 >> >>This is a special kind of bad bishop, the bishop is permanently dead. It would >>be easy to write something that could understand that the bishop is dead, but it >>would be hard to execute the code hundreds of thousands of times per second. >> > >>Put black's f7 pawn on g7 and black is suddenly doing lots better. > >And can save a few bucks as in my case. I think it is doable to write >code for this kind of situations only that in the 18 years I am working >now on Rebel I haven't seen such a case of a trapped bishop happening. >These guys surely know how to debug a chess engine. > >Ed > > >>bruce There are three issues: (1) sometimes you simply have to take your lumps and go home. This might be considered to be one of those kinds of positions where they are so rare, they aren't worth fixing. (2) you can also avoid this in a different way, namely the way I do this in my eval, by (a) penalizing blocked pawns and (b) rewarding potential pawn levers to make sure the position doesn't become so hopelessly blocked as the one you saw. CptnBlueBear will murder you with this if you aren't careful, as it is _exactly_ what he tries to do. And as a GM, it is very difficult to keep him from doing it without accepting a weakness or two that you really would prefer not to. (3) you can fix this in code. I did it once for Roman. But it was _very_ slow, for the good that it provided, and he later agreed that trying to avoid the blocked position just because it was blocked, rather than worrying about a hopelessly bad bishop, probably was more effective in most cases. The thing that worries me is that there are _hundreds_ more of these kinds of special cases that are left to discover. I have discovered many in my code. I am afraid I have only scratched the surface, yet I have over 50,000 blitz games vs GM players to go on. :(
This page took 0.01 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.