Improving SF passer code

[Lyudmil Tsvetkov]

f5 is the best move, but it creates a strong advanced protected pawn, being a storming pawn at the same time, and further limits the black knight.

[Lyudmil Tsvetkov]

[d]r2qk2r/1b3ppp/p2p1b2/2nNp3/1R2P3/2P5/1PN2PPP/3QKB1R w Kkq - 3 17


As Gaviota is a backward pawn expert even without having backward pawns eval in its code, does Gaviota find Rb7 above, with substantial white advantage?

[d]r1bqkb1r/1p3ppp/p1nppn2/8/2P1P3/N1N5/PP3PPP/R1BQKB1R b KQkq - 1 8

Why do you think Kasparov plays here d6-d5, sacrificing a pawn, just to get rid of the bind on the central d5 square?
And this, in the heat of the World championship match?

As a prominent bind/backward pawns expert, does Gaviota find d6-d5 above as the best move for black?

You are 4 years late

http://www.talkchess.com/forum/viewtopi ... 28&start=0

And this has nothing to do with backward pawns. It is about color weaknesses and outposts. The backward pawn is there with or without the sacrifice.

Miguel

You surprised me with this.

I presume you played the rook sacrifice for Gaviota in her place.

So, Gaviota is the only engine seeing the sacrifice and giving white advantage. You explained what makes Gaviota do so: big bonus for knight outpost on d5, penalty for low mobility piece on b7, bad black dark-coloured bishop.

I think most strong programs have those terms.
Why is it then that only Gaviota sees the sacrifice? Maybe the size of the bonus?

Until you give reasonable explanation, I am willing to accept conspiration theories.

The sacrifice has all to do with backward pawns, as, if there was not such a pawn on d6, which is the main feature of the position, the sacrifice would have been altogether impossible, as the black knight on b7 would have had good escape square on d6; but now, the d6 pawn prevents that.

[lucasart]

Here's a more interesting example:
[d]8/1pp5/p7/P1P5/8/8/8/8 w - - 0 1
Here, SF will give connected bonus to all 3 black pawns (2 phalanx and 1 supported), and will penalize both white pawns for being isolated. In reality, the two white pawns form an important bind on the b6 square.

Now you start to realise.

When will you push a patch with this?

It's not that simple. There is a reason why SF considers connected pawns not backward. I'm pretty sure changing that would be a regression:
* what if c5 isn't there ?
* what if there's a pawn on a7 ?
* what if the weak pawn is defended by a pawn (move everything down one rank and have a black pawn defend b6 in a7 and/or c7) ?

[michiguel]

[d]r2qk2r/1b3ppp/p2p1b2/2nNp3/1R2P3/2P5/1PN2PPP/3QKB1R w Kkq - 3 17


As Gaviota is a backward pawn expert even without having backward pawns eval in its code, does Gaviota find Rb7 above, with substantial white advantage?

[d]r1bqkb1r/1p3ppp/p1nppn2/8/2P1P3/N1N5/PP3PPP/R1BQKB1R b KQkq - 1 8

Why do you think Kasparov plays here d6-d5, sacrificing a pawn, just to get rid of the bind on the central d5 square?
And this, in the heat of the World championship match?

As a prominent bind/backward pawns expert, does Gaviota find d6-d5 above as the best move for black?

You are 4 years late

http://www.talkchess.com/forum/viewtopi ... 28&start=0

And this has nothing to do with backward pawns. It is about color weaknesses and outposts. The backward pawn is there with or without the sacrifice.

Miguel

You surprised me with this.

I presume you played the rook sacrifice for Gaviota in her place.

So, Gaviota is the only engine seeing the sacrifice and giving white advantage. You explained what makes Gaviota do so: big bonus for knight outpost on d5, penalty for low mobility piece on b7, bad black dark-coloured bishop.

I think most strong programs have those terms.
Why is it then that only Gaviota sees the sacrifice? Maybe the size of the bonus?

Until you give reasonable explanation, I am willing to accept conspiration theories.

You read it already. It is in the thread.

The sacrifice has all to do with backward pawns, as, if there was not such a pawn on d6, which is the main feature of the position, the sacrifice would have been altogether impossible, as the black knight on b7 would have had good escape square on d6; but now, the d6 pawn prevents that.

No, the backward pawn is BEFORE and AFTER the sacrifice. So, whatever the penalty is, it won't matter to decide if the sacrifice is good or not. It cancels out.

Miguel

[Lyudmil Tsvetkov]

Here's a more interesting example:
[d]8/1pp5/p7/P1P5/8/8/8/8 w - - 0 1
Here, SF will give connected bonus to all 3 black pawns (2 phalanx and 1 supported), and will penalize both white pawns for being isolated. In reality, the two white pawns form an important bind on the b6 square.

Now you start to realise.

When will you push a patch with this?

It's not that simple. There is a reason why SF considers connected pawns not backward. I'm pretty sure changing that would be a regression:
* what if c5 isn't there ?
* what if there's a pawn on a7 ?
* what if the weak pawn is defended by a pawn (move everything down one rank and have a black pawn defend b6 in a7 and/or c7) ?

It will not be a regression.

c5 is not necessary, the penalty is due just with a single white pawn, because usually, statistically if you want, the square in front of such a backward pawn on the 2nd rank will be controlled by enemy pieces rather than own ones. That is why the penalty is due.

As said, you want to consider such backward connected pawns just for the 2nd rank.
They might also be relevant for 3rd rank, with lower values, but chances are current SF will see liability only in the case of the 2nd rank.

I know what I am talking about, watching many SF games.

[Lyudmil Tsvetkov]

You might just want to push a patch with my suggested values for the backward connected array for the 2nd rank, please see the subthread in this thread.

If it does not pass, this is my last message on the forum.

[Lyudmil Tsvetkov]

No, the backward pawn is BEFORE and AFTER the sacrifice. So, whatever the penalty is, it won't matter to decide if the sacrifice is good or not. It cancels out.

Miguel

If there is one salient feature about the above position, it is the backward d6 pawn.

Such structures are known to be played along those lines.

You still did not acknowledge if you specifically tuned Gaviota eval terms to be able to cope with this position?