I meant what you also meant, but I have miscalculated this.Sven Schüle wrote: Which values do you mean by "the values would imply ..." here? If you mean minor=3.75/rook=5.50 then my calculator says 2 x 3.75 - 5.50 = 2, not 2.5. So probably you mean something else which I can't see yet.
Of course you are right, and 2*3.75 - 5.50 is 2 pawns. Nevertheless the question is still if this is too much (I don't think so) or rather too little.
The 'traditional material count' every beginner is teached first when he starts learning chess and which is pretty common among chess players < 2000 Elo (and also in not few amateur engines) although it estimates many material configurations very wrong:Sven Schüle wrote:As to your question: while traditional chess theory told us that R+P nearly equals two minors (except in case of a bishop pair), today it seems clear that it is closer to R+2P at least. To be honest: I don't know what the value should be but as a chessplayer I believe that values close to three pawns are highly exaggerated *for human chess play*. However, it may turn out to be quite different for engines. While parameter tuning for one engine may deliver good results with R+3P vs. two minors, another one may tend to more "human-like" R+2P or even less and get best results this way round.
{ P=1; N=3; B=3; R=5; Q=9 }
Here is N=B=3P and R+P=N+B.
In practical chess play I have seen many cases (also in my own games) where a rook and one or two pawns were traded for two minors, and I have always seen the two minors win. In some cases things like bishop pair or rook pair redundancy were involved, but not in all.
I think Rybka is able to evaluate material imbalances more exact here as in the imbalance table, every plausible case seems to be covered. Things like these can not be evaluated very exactly.Sven Schüle wrote:I guess there is no "general answer" since the positional evaluation is so different between engines, which makes it nearly impossible in my opinion to compare only the pure material value constants of two engines.
I just made a small experiment with Rybka 2.2n2 (no R3 available here): from the initial position I removed Nb1, Bc1 and Ra8, Pa7 and started a very quick analysis. The PV (e4 g6 Nf3 Bg7 c3 Nc6 Qa4 Nf6 e5 Nd5) showed a value of -0.95 after few seconds. Then I also removed Pc7, which gave -0.51 (Nf3 Nf6 e3 Nc6 c3 g6 d4 e6 Bd3 Bg7 O-O). Finally I removed Pd7 and the PV was "e3 Nc6 Bb5 Nf6 Nf3 e6 a4 Bd7 a5 Qb8 Nd4 Bd6" with a value of +0.01. So R+3P gave about an equal play, of course many positional factors add into this here. But interesting was that R+1P was not -2.00 but gave a PV with only about -1.00.
It is not representative, and it is also about search, not only about material value constants, I know. I just found it interesting.
Sven
