Author: Omid David
Date: 16:39:27 10/03/02
Go up one level in this thread
On October 03, 2002 at 19:18:16, Jeremiah Penery wrote:
>8/7p/6pP/k4pP1/b1p1pP2/KpPpP3/1P1P4/7Q w - - 0 1
>3k4/2p1p1p1/p1P1P1Pp/P6P/4K3/8/8/8 w
>8/4kr1b/4p3/rp1pPp1p/pPpP1PpP/P1P3P1/2K5/8 w
>8/4k3/8/p1p1p1p1/P1P1P1P1/8/2B1K3/8 w
>4b3/4k3/2p1p1p1/1pPpPpPp/pP1P1P1P/P2K4/3B4/8 w - - 0 1
>3B4/1r2p3/r2p1p2/bkp1P1p1/1p1P1PPp/p1P1K2P/PPB5/8 w - - 0 1
>4k3/8/1p1p4/pPpPp1p1/P1P1PpPp/5P1P/2BB4/K7 w
>
>
>This is a set of positions that most chess programs completely don't understand
>because the position is completely blocked. I have implemented some ability in
>Crafty to understand this type of position, with decent results. There are also
>a couple of interesting problems that have come up, particularly with the last
>position.
>
>[D]8/7p/6pP/k4pP1/b1p1pP2/KpPpP3/1P1P4/7Q w - - 0 1
>
>Static evaluation is now 0 here. The solution is supposed to be Qd1 <bishop
>move> {Kb5 Qh5!} Qxb3. The problem in solving this is that the evaluation after
>the given line is negative for white, so it doesn't want to play the
>'sacrifice'. But I consider it a good result that it knows this is a draw since
>it can't make progress.
>Normal Crafty 18.15 says near +5, while making the wrong move.
>
>[D]3k4/2p1p1p1/p1P1P1Pp/P6P/4K3/8/8/8 w
>
>Static evaluation 0, search returns instant 60 plies with drawscore.
>Normal Crafty says +1.4 or so.
>
>[D]8/4kr1b/4p3/rp1pPp1p/pPpP1PpP/P1P3P1/2K5/8 w
>
>Static 0 again, search says the same.
>Normal crafty has static score near -13, and wants to open the position, search
>score keeps dropping.
>
>[D]8/4k3/8/p1p1p1p1/P1P1P1P1/8/2B1K3/8 w
>
>Drawscore, static and by 60 ply search.
>Normal Crafty gives +3.3 for both.
>
>[D]4b3/4k3/2p1p1p1/1pPpPpPp/pP1P1P1P/P2K4/3B4/8 w - - 0 1
>
>Static score 0, instant 60 plies.
>Normal Crafty is similar, +0.09/+0.06
>
>[D]3B4/1r2p3/r2p1p2/bkp1P1p1/1p1P1PPp/p1P1K2P/PPB5/8 w - - 0 1
>
>Static evaluation of -5.93 here, but it finds the draw by search in 6 plies.
>Normal Crafty says -6.07, and wants to open the position by search, with
>dropping score.
>
>[D]4k3/8/1p1p4/pPpPp1p1/P1P1PpPp/5P1P/2BB4/K7 w
>
>This is the first problem position. It is evaluated statically as a draw, but
>once White sacrifices its dark-squared bishop for one of black's pawns, it no
>longer gets evaluated as a draw. No problem, right? Well, it keeps pushing it
>back into the horizon:
>
> 6 0.01 6.39 1. Bxa5 bxa5 2. Kb2 Ke7 3. Kc3 Kd7
> 6-> 0.02 6.39 1. Bxa5 bxa5 2. Kb2 Ke7 3. Kc3 Kd7
> 7 0.02 6.50 1. Bxa5 bxa5 2. Kb2 Ke7 3. Kc3 Kd7
> 4. Kd3
> 7-> 0.03 6.50 1. Bxa5 bxa5 2. Kb2 Ke7 3. Kc3 Kd7
> 4. Kd3
> 8 0.03 -- 1. Bxa5
> 8 0.03 0.00 1. Bxa5 bxa5 2. Kb2 Kd7 3. Bb3 Kc7
> 4. Kc3 Kb6
> 8 0.04 6.39 1. Ka2 Kd7 2. Kb2 Kc7 3. Bc3 Kb7 4.
> Bxe5 dxe5
> 8 0.05 6.50 1. Kb2 Kd7 2. Kc3 Kc7 3. Kd3 Kd7 4.
> Bxa5 bxa5 <HT>
> 8-> 0.05 6.50 1. Kb2 Kd7 2. Kc3 Kc7 3. Kd3 Kd7 4.
> Bxa5 bxa5 <HT>
> .......................................................
> 19 2.69 6.56 1. Kb2 Kd7 2. Kc3 Kc7 3. Kd3 Kd7 4.
> Bc3 Ke7 5. Bb3 Kd7 6. Be1 Kc7 7. Ba2
> Kd7 8. Bc3 Ke7 9. Bxe5 dxe5 10. Bb3
> 19-> 3.05 6.56 1. Kb2 Kd7 2. Kc3 Kc7 3. Kd3 Kd7 4.
> Bc3 Ke7 5. Bb3 Kd7 6. Be1 Kc7 7. Ba2
> Kd7 8. Bc3 Ke7 9. Bxe5 dxe5 10. Bb3
>
>No matter how deep I let it go, it always pushes the bishop sac into the last
>couple of plies. Is there any way I can solve this problem?
>Normal Crafty here says 7.77 static, and it doesn't have any captures in the
>search as long as it goes, score stays around 8.26.
>
>Does anyone have more positions they'd like me to try, or has anyone else worked
>on this kind of thing in their engine?
My under-development engine, detects the positions you mentioned as draw based
on static evaluation (seems that you have done something similar).
However, for the first and last positions it fails to detect the draw. Your last
position is really interesting; my program failed to detect the draw because of
the very reason you mentioned.
BTW, how much (in percentage or NPS) did the implemented draw detection slow
down the engine?
Omid.
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