Author: Robert Hyatt
Date: 20:53:57 08/14/02
Go up one level in this thread
On August 14, 2002 at 06:23:31, Marc van Hal wrote: >On August 13, 2002 at 16:09:53, Uri Blass wrote: > >>On August 13, 2002 at 15:18:04, Vincent Diepeveen wrote: >> >>>On August 13, 2002 at 07:23:38, Uri Blass wrote: >>> >>>>My definition for a sacrifice or blunder >>>>is a move that lose material based on >>>>the depth that programs can see. >>>> >>>>The definition of losing material is based on >>>>the material values 1,3,3,5,9. >>> >>>with all respect but your table is outdated in advance. >>> >>> a) 2 rooks are weaker than a queen in 99.9% of all cases >>> the computer sees 2 rooks for a queen >> >>It is not the case based on experience with movei but I still evaluate >>queen as almost 2 rooks(difference of less than 0.5 pawn). >> >>I evaluate queen as about 10 and rook as slightly more than 5. >> >>> b) this table indicates that giving away 2 pieces for a rook+pawn >>> is great >> >>I know and I evaluate bishop or knight as about 3.5 in movei(I cannot give exact >>value because the evaluation is based on the square of the piece and I have 64 >>values for every piece based on the square but I still call it a sacrifice if a >>program to give 2 pieces for rook and 2 pawns). >> >> >> >>For m >>> c) giving away a piece for 3 pawns is great according to this >>> table, especially if we know that one of the 3 pawns gets >>> a passer >> >>I evaluate 3 pawns as less than a piece in movei. >> >>You also assume here that 1 is for a pawn that is not a passed pawn. >>It is possible to assume that 1 is the average value of the pawn and in that >>case pawns that are not passed pawns are evaluated as less than 1. >>> >>>So the definition is not correct! >>> >>>In diep queen = 11.5 pawns >>> rook = 5.5 pawns >>> piece = 3.6 pawns >>> >>>and i have special cases to catch weird cases which sometimes happen. >>> >>>>For a clear definition we need to compare >>>>the evaluation of a program with mainly material evaluation before and after the >>>>move when we give it an hour to search. >>>> >>>>A program with mainly material evaluation is defined to be >>>>a program with positional scores >>>>that are always smaller than 0.5 pawns. >>> >>>again a wrong assumption. Some very old >>>programs (like some at dedicated machine) have like 2 extra >>>rules in evaluation which always is like "if passer on 2nd row >>>then score += 3.0" >> >>In that case they have big positional scores so I can say that they sacrificed. >>I think that this bonus is not justified. >> >>Movei still does not evaluate passed pawns but inspite of this fact it is at >>similiar level to some programs that evaluate passed pawns like amateur. >> >>I can see cases when movei wins when it seems to me that the evaluation of the >>opponent for passed pawns is too high. >> >>> >>>In short especially a few very materialistic beancounters are tuned >>>to very high scores, whereas others with loads of chess knowledge >>>usually are more relaxed in this respect. >> >>I did not say that programs with more knowledge sacrifice more material. >> >>Uri > > >By increasing the valeu of a pawn it is more likely a piece will be sacreficed! >Marc This is the reason I gave up on trying to diddle with the piece values to solve a known problem... such as two pieces for rook and pawn. I simply added code to detect the known problems (two pieces better than rook and pawn, three pieces better than queen, etc) and therefore don't worry about the bad trades happening any longer...
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