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Subject: Re: test position (a pawn endgame)

Author: Simon Finn

Date: 03:28:21 10/18/01

Go up one level in this thread


On October 17, 2001 at 13:27:46, Robert Hyatt wrote:

>On October 16, 2001 at 08:13:00, Uri Blass wrote:
>
>>Can your program see the win?
>>
>>Note that yace needs a long time to avoid Kd4 that is clearly not the fastest
>>way to win even if it wins because after 1.Kd4 Kd8 you get a repetition that
>>only humans understand and computers do not know to evaluate it as a repetition.
>>
>>Note that I analyzed this position some years ago and my conclusion was that
>>white can win by 1.b6 cxb6 2.a6 bxa6 3.c6
>>
>>Yace does not understand the idea and it seems that yace's main line is leading
>>to draw.
>>
>>yace also cannot see deep in the pawn endgame and I wonder if avoiding qsearch
>>can help it.
>>
>>Tiger can get bigger depth but it does not help it to see 1.b6 in a short
>>time(maybe 1.Kd3 also wins but it seems to me a strange way to win when 1.b6 is
>>the simple way0
>>
>>New position
>>[D]4k3/pppppppp/8/PPPPPPPP/4K3/8/8/8 w - - 0 1
[snip]
>>Uri
>
>
>To avoid a lot of calculating, I would probably try g6 first, and use
>the "sneaker" idea to create a passed pawn over there.  Once the black king
>moves in that direction, b6 to do a "sneaker" on the other side is a simple
>win.

That doesn't work well because the White king is badly placed on e4.

1. g6 fxg6 2. h6 gxf5+ 3. Kxf5 gxh6

denies White the king-side passed pawn.

That's why Tiger's 1. Kd3 is a good idea - White can follow up
with b6 and g6 (or vice-versa) without worrying about checks.
This produces (at worst) passed pawns on the c and f files
which can promote without assistance from the king.

>
>(note "sneaker" is the name I often saw applied to the idea of playing
>b6.  if black plays axb6 then white plays c6.  If bxc6 then a6 wins.  If
>bxa5 then cxb7 wins.)
>
>Note that I don't see an instant win with your suggestion of b6, axb6 c6, as
>I play dxc6 and you don't have a passer yet.

After recapturing, White intends to follow up with f6, producing
passed c and (at worst)e pawns. With the help of his king, one of
these queens before Black can promote.

>
>At shallow searches, Crafty seems to go for e6, which will dislodge the d
>pawn and make the queen-side sneaker work if the king can be decoyed
>away.

Unfortunately, it can't because there's no way to break into the k-side
once the f-pawns have been exchanged.

>
>I haven't spent a lot of time looking at this, of course, so your analysis
>could be right for other reasons.  But I don't see how b6 wins instantly as
>it would if the king was over one more square and the d pawn (for black) was
>missing.

Simon



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