bob wrote:I realize that. And that is why "bishop pair" is not folded into those pc/sq tables. Those are per-piece, and simply increasing the value of one bishop won't cut it for a bishop-pair bonus.
Yes, but the material tables can include it. They are exactly intended to describe non-linear effects of the materil composition. But they are blind to positioning of the pieces.
In Xiangqi the material tables are even more important than in Chess: there are pieces that have no value at all unless the opponent has offensive material: te pieces that are forbidden to cross the river. They can only be used in defense, and derive their value solely from what the opponent has to attack. You can be 4 such piece ahead, and it can still be a draw by rule (insuff. mating material).
How can the material balance tables include something that does not apply in all positions? The bishop pair score is one of those ideas. Putting it in the pc/sq table is problematic. Because it should not be included in any position with two bishops for the same side. There are other constraints that have to be met before a realistic bishop pair score can be factored in. A bishop pair with a bad bishop is worthless and should actually get a negative score, not a bonus for two bishops.
A bishop and knight vs a rook and pawn is a more natural case. The two minors are almost always better except in certain types of endgames where the extra pawn becomes decisive.
Doesn't the "bad bishop" score solve the bishop pair dilemma when a wall is formed?
It seems to me that the bishop pair bonus will again become valuable if you punch a hole in the wall. So as long as the bad bishop score is bigger than the bishop pair score, it seems to me that it would take care of itself.
bob wrote:I realize that. And that is why "bishop pair" is not folded into those pc/sq tables. Those are per-piece, and simply increasing the value of one bishop won't cut it for a bishop-pair bonus.
Yes, but the material tables can include it. They are exactly intended to describe non-linear effects of the materil composition. But they are blind to positioning of the pieces.
In Xiangqi the material tables are even more important than in Chess: there are pieces that have no value at all unless the opponent has offensive material: te pieces that are forbidden to cross the river. They can only be used in defense, and derive their value solely from what the opponent has to attack. You can be 4 such piece ahead, and it can still be a draw by rule (insuff. mating material).
How can the material balance tables include something that does not apply in all positions? The bishop pair score is one of those ideas. Putting it in the pc/sq table is problematic. Because it should not be included in any position with two bishops for the same side. There are other constraints that have to be met before a realistic bishop pair score can be factored in. A bishop pair with a bad bishop is worthless and should actually get a negative score, not a bonus for two bishops.
A bishop and knight vs a rook and pawn is a more natural case. The two minors are almost always better except in certain types of endgames where the extra pawn becomes decisive.
Doesn't the "bad bishop" score solve the bishop pair dilemma when a wall is formed?
It seems to me that the bishop pair bonus will again become valuable if you punch a hole in the wall. So as long as the bad bishop score is bigger than the bishop pair score, it seems to me that it would take care of itself.
Maybe or maybe not. The point being that you do not want a bad pair, because in those positions, knights are often superior and a B for N trade is an advantage. A bad bishop still gets the pair bonus, just a penalty for mobility that offsets. I've not seen many programs that understand "bad bishop" which means a static pair bonus is a bad idea. Particularly if it is 1/2 pawn or higher.
In Joker I count Pawns on light and dark squares separately, so a material table indexed by those numbers could account for a Bishop with may Pawns on its color being worse than one with only few.
It would be interesting to se if the drop of Bishop value seen in Larry Kaufman's analysis could be specified by color of the Pawns, rather than just the average. Did he already do that?
hgm wrote:In Joker I count Pawns on light and dark squares separately, so a material table indexed by those numbers could account for a Bishop with may Pawns on its color being worse than one with only few.
It would be interesting to se if the drop of Bishop value seen in Larry Kaufman's analysis could be specified by color of the Pawns, rather than just the average. Did he already do that?
I am not sure. In the context of bishop pair it would not seem to matter since pawns not on the color of one bishop will interfere with the other... It is really more about which squares the pawns are on and how they interfere with the bishop's ability to move.
hgm wrote:In Joker I count Pawns on light and dark squares separately, so a material table indexed by those numbers could account for a Bishop with may Pawns on its color being worse than one with only few.
It would be interesting to se if the drop of Bishop value seen in Larry Kaufman's analysis could be specified by color of the Pawns, rather than just the average. Did he already do that?
I don't think that counting pawns on squares is good enough. The nature of the formation is even more important. For instance:
[d]4k1b1/8/8/2p1p1p1/2P1P1P1/p7/P2BP3/4K3 w - -
[d]4k3/3n1n2/8/2p1p1p1/2P1P1P1/p3B3/P3P3/1B2K3 w - -
[d]4k3/8/5b2/2p1p1p1/1pPpPpP1/1P1P1P2/2B5/4K3 w - -
[d]4k3/8/4b3/2p1p1p1/1pPpPpP1/1P1P1P2/3B4/4K3 w - -
[d]2n1k3/6n1/2p1p3/2PpPp2/3P1P2/8/1BB5/4K3 w - -
[d]1n6/3k4/2p1n3/2PpP3/3p1p2/3P1P2/1BB5/4K3 w - -
