Author: Howard Exner
Date: 17:20:55 07/23/98
Go up one level in this thread
On July 23, 1998 at 15:17:03, Robert Hyatt wrote: >On July 23, 1998 at 13:48:10, Bruce Moreland wrote: > >> >>On July 23, 1998 at 12:58:20, Robert Hyatt wrote: >> >>>The major move that Crafty didn't like was the Qh5+ move which traded the knight >>>on h8 for black's remaining two pawns. Crafty has specific eval code that says >>>if it is down a piece, even with three pawns for it, it isn't going to be happy >>>unless all the pieces are gone except for that one extra piece for the opponent. >> >>Black got two pieces for a rook and three pawns. You consider this being down a >>piece? >> >>bruce > >I don't count the pawns in this piece of code. I look and see "rook" for "two >pieces" and say "*bad*" for the rook side. Ditto if I get a piece for two or >three pawns. I say "bad" for the side with the pawns. How bad? Varies, but >the penalty is over a pawn at present, to avoid doing the ugly B+N for a R+P, >commonly on f2/f7, or a knight for 2 or 3 pawns to create some passers as well. > >This penalty scales down (piece for pawns) as pieces are traded, because I'd >much rather have 3 pawns against a knight or bishop than have the bishop and >only be able to hope for a draw. > >Ed faked around with the vaue of a pawn to avoid the piece for pawns trade. I >used to muck around with the piece and pawn values to discourage this. But I >got tired of the problems that caused, and, in fact, the current "penalty" is >exactly how I do this as a human. I (and Crafty) would gladly sac a piece for >two or three pawns around the king if there are attacking chances. But not just >to call it "even" since the extra piece becomes a problem... > >So I consider N for 3P's to be +1.00 for the side with the N, if there are no >other positional factors to change this. Evaluating those positional factors are I think crucial to determining this kind of exchange. Seems like a monumental task for programmers to put this into code as it is tough enough for strong humans to determine when or when not to swap. One general rule of thumb in every strategy book I've read was to avoid giving up the two minors for Rook and pawns in the opening and middle phase of the game. The logic ran something like - minor pieces can obtain nice outposts in these phases of the game while pawns are limited in their freedom of movement. Rooks too with their battering ram mentality become felt more in latter stages of the game. How many 30 move games have the winning side attributing victory to their well placed rooks? >I consider a R vs BN (or any two >pieces) to be -2 for the R side (-1 for normal material difference, -1 for >what I call a "bad trade")...
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.