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This is an example of a passed but doubled pawn:

[d] 8/r5kp/p2RB1p1/3P4/1p1P4/nP4P1/P3K2P/8 b - - 0 36

(from Fischer-Larsen, Denver (m/1) 1971)

What score does your program give to the pawn on d4? Mine recognizes it as both passed and doubled gives a small minus score but maybe White should get more credit for such pawns.

--Jon

jdart wrote:This is an example of a passed but doubled pawn:

[d] 8/r5kp/p2RB1p1/3P4/1p1P4/nP4P1/P3K2P/8 b - - 0 36

(from Fischer-Larsen, Denver (m/1) 1971)

What score does your program give to the pawn on d4? Mine recognizes it as both passed and doubled gives a small minus score but maybe White should get more credit for such pawns.

--Jon

I only count the most advanced one as passed. But even that has a problem since with the other pawn, a piece can't support the lead passer from the back so it will miss out on all sorts of bonuses.

I think sometimes the "behind" pawn is weak, but still, there are cases where it can be beneficial because White has two chances to promote on that file, i.e.
can give up a pawn and still have a passer.

--Jon

bob wrote: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.

jdart wrote:This is an example of a passed but doubled pawn:

[d] 8/r5kp/p2RB1p1/3P4/1p1P4/nP4P1/P3K2P/8 b - - 0 36

(from Fischer-Larsen, Denver (m/1) 1971)

What score does your program give to the pawn on d4? Mine recognizes it as both passed and doubled gives a small minus score but maybe White should get more credit for such pawns.

--Jon

In Deuterium it is a pawn with doubled-pawn penalty plus isolated-pawn penalty. But giving a bonus to it if it reaches the 6th rank is an interesting try for me.

mar wrote:

bob wrote: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.

mar wrote:

bob wrote: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 still do that. IE rook has to directly attack the pawn. So only the closest rook gets that bonus. Although I do add this in the passed pawn scoring now, trying to organize things a bit better and not having passed pawn code scattered from can to can't.

Joost Buijs wrote:

mar wrote:

bob wrote: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.

It probably depends on the values one use, but for Rodent it worked best to score the second of a doubled passers like a candidate passer (which means midgame bonus 0, endgame bonus: passer_bonus / 3.

bob wrote:

Joost Buijs wrote:

mar wrote:

bob wrote: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.