passed but doubled pawns

[bob]

I only count the most advanced one as passed.

I do the same, actually giving the same bonus to doubled passer(s) doesn't seem logical to me (doubled penalty won't compensate for that), so maybe having a special "doubled passer" bonus? - if it's worth it which I doubt...
Back when I had rook behind passer bonus, I also made sure I only gave bonus to one rook if they were doubled.

I only score the front pawn as passed, but it can be a mistake, in the past I saw several games with doubled passers where the second passer secured the win.

Don't you think you have to give an extra bonus when there is a doubled rook behind the passer instead of a single one?
I have the feeling that you should although I never tried and tested it in practice.

I think the second rook can be used better elsewhere. IE one term I used to have was that a passed pawn became more valuable if one of the files beside it was open AND I had a rook on that file (there is a name for this, maybe in Kmoch's book, but I don't remember the term). The usual benefit for a single rook behind the passer is that if the opponent blockades the pawn, the blockader can't move or the pawn will advance (since the blockader attacks the next square, but so does the rook after the pawn moves). Putting a second rook behind the pawn doesn't add anything in most cases, and the rook is doing little since it is not on an open file where it can swing to any part of the board.

When the pawn is blocked it is not very useful to have 2 rooks pushing from behind.
In case the pawn is not blocked it all depends upon how many times the squares in front of the pawn are attacked by the opponent.
I can think of several situations where 2 rooks behind the pawn can be useful.
On the other hand when such a situation arises the search will also find it although it will probably be somewhat later.

The issue is, if the pawn can advance because of the second rook, in today's 30+ ply searches we ought to be able to see that moving the second rook behind the pawn is good, temporarily. But a single rook behind the pawn ties down the opponent's blockader pretty well and is a long-term positional problem for the opponent.

[jdart]

Nice win today in the Nakamura-Hammer game (http://en.chessbase.com/post/norway-01- ... ular-round). Nakamura did at one point (move 49) have two rooks behind his passer. But I agree this may not deserve a positional bonus.

--Jon