On-line blitz tourney December

[hgm]

My point was that it is more difficult do tie up a stronger piece for 100%. A Knight stopping a passer has to stay close, and cannot even be used for King interdiction. A Rook stopping a 7th-rank passer has much more lattitude to manouevre without dropping its guard. It could hold off two passers at the same time (when they are not connected). In addition, the Rook actually attacks the passer it is blocking. So the other side will need something to defend the passer. So it is not that the passer in itself can bind the Rook, like it can bind a Knight or Bishop; it is passer plus constant attention of something else that binds the Rook. E.g. using a Knight to protect the Rook, the passer is only binding an exchange.

[Evert]

When you have no minors, opponent passers might actually need to get an extra bonus.

I suspect that's right. The value of a passer is (meaning: asymptotically approaches) the value of the least valuable piece that the opponent is willing to sacrifice to stop the pawn from promoting. So if he only has a rook, then the value of the passer is that of a rook - as long as the pawn can promote to something more valuable.
This seemed too much hassle to implement, but it might be important in a game like grand chess where the promotion options depend on the pieces that were captured.
Let's just say that this is not the most obvious thing wrong with Sjaak's passed pawn evaluation.

[Roger Brown]

My point was that it is more difficult do tie up a stronger piece for 100%. A Knight stopping a passer has to stay close, and cannot even be used for King interdiction. A Rook stopping a 7th-rank passer has much more lattitude to manouevre without dropping its guard. It could hold off two passers at the same time (when they are not connected). In addition, the Rook actually attacks the passer it is blocking. So the other side will need something to defend the passer. So it is not that the passer in itself can bind the Rook, like it can bind a Knight or Bishop; it is passer plus constant attention of something else that binds the Rook. E.g. using a Knight to protect the Rook, the passer is only binding an exchange.

Ah, thank you for the usual clear explanation.

Later.