Author: Robin Smith
Date: 23:00:29 01/20/02
Go up one level in this thread
On January 20, 2002 at 10:25:50, David Rasmussen wrote: >On January 20, 2002 at 10:12:28, Uri Blass wrote: > >>On January 20, 2002 at 09:41:48, David Rasmussen wrote: >> >>>On January 20, 2002 at 09:29:24, Severi Salminen wrote: >>> >>>>On January 20, 2002 at 09:01:50, David Rasmussen wrote: >>>> >>>>>There must be a value system of material that takes care of all special cases. >>>>> >>>>>1,3,3,5,9: >>>>> >>>>>Has the following problems: >>>>>3 pawns for bishop or knight is almost always a bad idea. >>>>>2 knights/bishops for rook and pawn is almost always a bad idea. >>>>>2 rooks for queen is often not a good idea. >>>>>3 knights/bishops for a queens is often not a good idea. Then again, often it is >>>>>:) >>>>> >>>>>What is your best bet? >>>> >>>>And sometimes a Bishop is better than a knight. So: >>>> >>>>P=1, B>N>3*P, R+P>2*B, Q>2*R and Q>3*B. In the general case, two rooks are considered stronger than a queen, not weaker. Of course there are always the many exceptions, for example the queen is beter at picking off numerous weak isolated pawns, but in general Q>2*R is not correct. Also Queen is usually more or less equal to 3 minor pieces, not greater. >>>>So maybe P=1, N=3.2, B=3.4, R=6, Q=13? Q=11 would be a beter choice. 13 is way too high. Also, Euwe's formula of 1,3.5,3.5,5.5,10 is much better than the classic 1,3,3,5,9. >>>>Severi >>> >>>I don't want to score bishop higher than knight. It depends on dynamic factors >>>that should be in evaluation anyway. I just want to avoid extra code to evaluate >>>special cases, as Crafty does. I think it is possible. >>> >>>/David >> >>There is no answer for your questions. >> >>It is even not possible to know what is the meaning of P=1 >>because the value of the pawn is dependent in the square of the pawn. >> >>If you do not use piece square table for pawns then your program may be weak >> >>If you use piece square table for pawns than P=1 is eqvivalent to P=1.2 when you >>only change the piece square table for the pawns. >> >>Uri > >Look, I am not talking about perfect evaluation here. I am talking about a >mature evaluation function, but instead of evaluating material special cases >(three pawns for a bishope etc.) as crafty does, I think all of these _material_ >special cases can be done with material values alone. All the other evaluation >stuff will still be there. > >/David This is all elimentary algebra. Just write 5 equations for the 5 unknowns (values for P, N, B, R, Q) and solve. One possible solution: If you assume: P=1 N=B R+2P=2N N=4P Q+P=2R Then solving yields the result: P=1 N=4 B=4 R=6 Q=11 Different, perhaps more complex equations will give different results. And none will be completely satisfactory .... there are too many exceptions. Robin
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