Bishop Mobility ?

[Henk]

At about 1:02:30 in this video Karpov shows a position where two knights are stronger than two bishops while one of it's bishops has excellent mobility "but is controlling an empty diagonal". So that means counting number of moves is no good measure.

https://www.youtube.com/watch?v=FVcpelqT_Dw

[bob]

At about 1:02:30 in this video Karpov shows a position where two knights are stronger than two bishops while one of it's bishops has excellent mobility "but is controlling an empty diagonal". So that means counting number of moves is no good measure.

https://www.youtube.com/watch?v=FVcpelqT_Dw

Doesn't mean that at all. It just means that the evaluation has to see the strengths of the two knights, and the fact that one of the bishops has one possible move and is "biting on granite" where it is blocked by the enemy pawn chain.

Mobility is always a "general guideline" that has to be evaluated in the context of the entire board.

[Henk]

There is a problem that mobility also counts moves that make no sense at all. So theoretically if a position is encountered with one very good move and a position with thirty bad or useless moves it will select the second one because the second has far better mobility.

[Karlo Bala]

At about 1:02:30 in this video Karpov shows a position where two knights are stronger than two bishops while one of it's bishops has excellent mobility "but is controlling an empty diagonal". So that means counting number of moves is no good measure.

https://www.youtube.com/watch?v=FVcpelqT_Dw

[d] 1r1qr1k1/1bp2ppp/3p1b2/1N1P4/2Q1P3/5N1P/R4PP1/4R1K1 b - - 0 1

I’m not going to argue with the world champion, just try to explain. The darksquare bishop is not great but it controls a lot of squares and it is not a bad piece for sure. Main weaknesses in black position are pawns on c7-d6, and the lightsquare bishop. As Karpov said, white is better, but not more.

[bob]

There is a problem that mobility also counts moves that make no sense at all. So theoretically if a position is encountered with one very good move and a position with thirty bad or useless moves it will select the second one because the second has far better mobility.

The issue is this. Is more mobility good or bad in the MAJORITY of chess positions. There is no one-size-fits-all that works everywhere, so we use that which works in the majority of cases. Which mobility does (although I do not just count legal moves, I have weighting based on specific squares, myself.

[AlvaroBegue]

There is a principle I never implemented myself, which is that bishops are less valuable if all the pawns are on the same side of the board. A big part of the bishop superiority over the knight in open positions comes from the ability to control pawns even at great distances. A knight is easily overwhelmed by passed pawns on both sides of the board.

In this particular position white doesn't have a pawn in columns a, b or c, so perhaps that makes the black bishops less valuable.

[cdani]

There is a principle I never implemented myself, which is that bishops are less valuable if all the pawns are on the same side of the board.

I have a little bonus in Andscacs for the bishop if all the pawns are in the same side (abcd/efgh) of the board. It was some little win.