Testposition Opposite coloured Bishops

Discussion of anything and everything relating to chess playing software and machines.

Moderators: hgm, Rebel, chrisw

User avatar
Eelco de Groot
Posts: 4565
Joined: Sun Mar 12, 2006 2:40 am
Full name:   

Testposition Opposite coloured Bishops

Post by Eelco de Groot »

What does your favorite engine say here? How long to see that you have to give up, resistance is futile :)

This came up in a testposition from Ma Laoshi

Stockfish thinks "almost a draw" (correction only for the material deficit of two pawns) because of opposite coloured bishops, even with a passed pawn duo :P

Lastest Serpent tries to correct it but it has not been tested in the rootposition here, the correction may be wrong in the general case with more than pawn total. So it still may not find 1. c6 even after days of searching, I don't know yet.


[D]8/2B5/p1b3p1/1p3k2/1P6/P4p2/5K2/8 w - -

Engine: Rainbow Serpent 20160903_016 HT (7 threads i7 Family 6 Model 94 Stepping 3 3408 MHz Quadcore, 512 MB)
Experimental opp. col. bishop correction in eval
by T. Romstad, M. Costalba, J. Kiiski, G. Linscott

34/38 0:01 -2.81 10.Ke3 Kg4 11.Kf2 Bd5 12.Bd6 g5
13.Ke3 Bb7 14.Bc7 Kh3 15.Kf2 Bc6
16.Bd6 Kg4 17.Ke3 Be4 18.Be5 Kf5
19.Bb8 Bb7 20.Bd6 Ba8 21.Bc7 Kg4
22.Kf2 Bd5 23.Bd6 (19.395.204) 17379

35/38 0:03 -2.81 10.Ke3 Kg4 11.Kf2 Bd5 12.Bd6 g5
13.Ke3 Bb7 14.Bb8 Ba8 15.Bd6 Kh4
16.Be5 g4 17.Kf2 Kh3 18.Bc7 Bb7
19.Bg3 Bd5 20.Bf4 Bc4 21.Bc7 Bd3
22.Be5 Bf5 23.Bg3 (55.152.594) 18130

36/38 0:04 -2.81 10.Ke3 Kg4 11.Kf2 Bd5 12.Bd6 g5
13.Ke3 Bb7 14.Kf2 Be4 15.Bb8 Kh3
16.Bc7 g4 17.Be5 Kh4 18.Bf4 Bf5
19.Bg3+ Kh3 20.Bc7 Bd3 21.Be5 Kh4
22.Bf4 Bg6 23.Be5 (78.267.003) 18295

37/40 0:05 -2.81 10.Ke3 Kg4 11.Kf2 Bd5 12.Bd6 g5
13.Ke3 Bb7 14.Kf2 Be4 15.Bb8 Kh3
16.Bc7 g4 17.Be5 Kh4 18.Bf4 Bf5
19.Bg3+ Kh3 20.Bc7 Bd3 21.Be5 Kh4
22.Bf4 Bg6 23.Be5 (91.893.812) 18247

38/42 0:05 -2.81 10.Ke3 Kg4 11.Kf2 Bd5 12.Bd6 g5
13.Ke3 Bb7 14.Kf2 Be4 15.Bb8 Kh3
16.Bc7 g4 17.Be5 Kh4 18.Bf4 Bf5
19.Bg3+ Kh3 20.Bc7 Bd3 21.Be5 Kh4
22.Bf4 Bg6 23.Be5 (104.048.486) 18247

39/42 0:08 -2.81 10.Ke3 Kg4 11.Kf2 Bd5 12.Bd6 g5
13.Ke3 Bb7 14.Kf2 Be4 15.Bb8 Kh3
16.Bc7 g4 17.Be5 Kh4 18.Bf4 Bf5
19.Bg3+ Kh3 20.Bc7 Bd3 21.Be5 Kh4
22.Bf4 Bg6 23.Be5 (147.331.551) 18272

40/43 0:10 -2.89-- 10.Ke3 Kg4 (194.858.109) 17909

40/43 0:12 -2.97-- 10.Ke3 Kg4 (220.994.826) 17819

40/43 0:14 -3.09-- 10.Ke3 Kg4 (251.305.192) 17595

40/43 0:16 -3.26-- 10.Ke3 g5 (284.125.816) 17435

40/47 0:17 -3.49-- 10.Ke3 g5 (310.374.230) 17359

40/47 0:19 -3.80-- 10.Ke3 g5 (339.984.195) 17237

40/51 0:26 -4.20-- 10.Ke3 g5 (448.543.735) 16954

40/51 0:36 -4.22 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Ke1 Bc2 15.Kf2 Bd1
16.Bc7 Kf5 17.Ke1 Be2 18.Bd8 g4
19.Bc7 Bc4 20.Bg3 Ke4 21.Bc7 Be6
22.Bd6 Kd3 23.Bc7 (623.584.846) 16954

41/51 0:46 -4.22 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Ke1 Bc2 15.Kf2 Bd1
16.Bc7 Kf5 17.Ke1 Be2 18.Bd8 g4
19.Bc7 Bc4 20.Bg3 Be6 21.Kf1 Ke4
22.Kf2 Bb3 23.Bc7 (787.261.097) 16896

42/51 0:56 -4.31-- 10.Ke3 g5 (949.357.248) 16786

42/51 1:03 -4.31 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Ke1 Bd3 15.Kf2 Bc2
16.Be5 Bf5 17.Bc3 Bd3 18.Bd2 Bc4
19.Be1 Be2 20.Bd2 Kf5 21.Ke3 Bd1
22.Bc3 g4 23.Be1 (1.077.224.099) 16910

43/51 1:21 -4.31 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Ke1 Bd3 15.Kf2 Bc2
16.Be5 Bf5 17.Bc3 Be6 18.Be5 Bd5
19.Bh2 Kf5 20.Ke1 Bc6 21.Bd6 Ke4
22.Bg3 Ke3 23.Bf2+ (1.381.260.564) 17028

44/51 1:31 -4.31 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Ke1 Bd3 15.Kf2 Bc2
16.Be5 Bf5 17.Bh2 Be4 18.Bd6 Bg6
19.Ke3 Bf5 20.Be5 Bd3 21.Kf2 Be2
22.Bc7 Kf5 23.Kg3 (1.558.439.227) 17009

45/51 1:59 -4.31 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Ke1 Bd3 15.Kf2 Bc2
16.Bh2 Be4 17.Bd6 Bf5 18.Bc7 Bg6
19.Bb6 Bf7 20.Bc7 Bd5 21.Ke3 Be4
22.Kf2 Bf5 23.Bb6 (2.024.832.702) 16926

46/51 2:19 -4.31 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Ke1 Bd3 15.Kf2 Bc2
16.Bh2 Be4 17.Bd6 Bd5 18.Bc7 Bc4
19.Be5 Be2 20.Bc7 Kf5 21.Ba5 g4
22.Kg3 Bd3 23.Kf2 (2.365.624.177) 17001

47/55 2:37 -4.31 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Ke1 Bd3 15.Kf2 Bc2
16.Bc7 Bf5 17.Bb6 Be6 18.Ba7 Bf7
19.Kg1 Bd5 20.Kf2 Be4 21.Bb6 Kf4
22.Bc7+ Kf5 23.Ke3 (2.682.697.267) 17018

48/59 3:43 -4.39-- 10.Ke3 g5 (3.808.143.891) 17003

48/59 4:33 -4.39 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Ke1 Bd3 15.Kf2 Bc2
16.Bd6 Bb3 17.Bc5 Bd1 18.Be3 Be2
19.Ba7 Kf5 20.Be3 g4 21.Kg3 Bc4
22.Bc5 Bd5 23.Kf2 (4.654.400.539) 17041

49/60 6:37 -4.39 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Kf1 Bc2 15.Kf2 Bd1
16.Bd6 Kf5 17.Be7 Kf4 18.Bd6+ Kg4
19.Bg3 Be2 20.Be5 Bd3 21.Ke3 Bg6
22.Bc7 Bc2 23.Be5 (6.813.042.612) 17160

50/60 7:32 -4.47-- 10.Ke3 g5 (7.712.140.032) 17054

50/63 9:59 -4.47 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Kf1 Bc2 15.Kf2 Bd1
16.Bd6 Kf5 17.Ke1 Bb3 18.Kf2 Ke4
19.Bf8 Bd5 20.Be7 g4 21.Bc5 Bc6
22.Kg3 Bd7 23.Kf2 (10.336.525.420) 17230

51/63 11:23 -4.47 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Bd7
13.Bb8 Bf5 14.Kf1 Bc2 15.Kf2 Bd1
16.Ke1 Be2 17.Bc7 Bc4 18.Kf2 Bb3
19.Bd6 Be6 20.Bc7 Bf5 21.Bb8 Bc2
22.Bd6 Bg6 23.Bb8 (11.819.670.723) 17289

52/63 16:27 -4.55-- 10.Ke3 g5 (17.566.964.128) 17783

52/63 26:32 -4.55 10.Ke3 g5 11.Bh2 Kg4 12.Kf2 Be4
13.Bd6 Bd3 14.Bh2 Be2 15.Bd6 Kf5
16.Bc5 g4 17.Bb6 Bd1 18.Ke1 Bc2
19.Bc7 Ke4 20.Bg3 Bb3 21.Bc7 Be6
22.Bg3 Bd5 23.Kf1 (29.376.554.906) 18442

best move: Kf2-e3 time: 28:13.250 min n/s: 18.442.751 nodes: 31.164.085.855
Debugging is twice as hard as writing the code in the first
place. Therefore, if you write the code as cleverly as possible, you
are, by definition, not smart enough to debug it.
-- Brian W. Kernighan
Top
Lyudmil Tsvetkov
Posts: 6052
Joined: Tue Jun 12, 2012 12:41 pm

Re: Testposition Opposite coloured Bishops

Post by Lyudmil Tsvetkov »

Too big advantage for black, Eelco.

a3 pawn is weak, 2 connected passed pawns, no possible fortress in the center.

My latest eval rule on opposite bishops is something like: if score<=100cps scale by some factor, otherwise do not scale. Of course, it will all depend on your eval, fortress recognition, etc.
Top
Paloma
Posts: 1167
Joined: Thu Dec 25, 2008 9:07 pm
Full name: Herbert L

Re: Testposition Opposite coloured Bishops

Post by Paloma »

Why is the white pawn on c5 disappeared :?:
Top
BeyondCritics
Posts: 396
Joined: Sat May 05, 2012 2:48 pm
Full name: Oliver Roese

Re: Testposition Opposite coloured Bishops

Post by BeyondCritics »

Do you believe in a win for black here? It is not clear to from your posting, but nevertheless after some preliminary analysis, i assume it is winning.
[D]8/2B5/p1b3p1/1p3k2/1P6/P4p2/5K2/8 w - -

Black can not win with g and f pawns alone, so in order to make progress, coming to a3 is absolutely required. Checking that plan, we see that with the a3 pawn gone, it is an easy win, using the breakthroughs a5 and g3 and zugzwang if needed. E.g move the king to d1, bishop to c6, play g5-g4 and then ...g3+, Kxg3 - Ke2 and then finally ...a5, bxa5 - b4 winning.

But how to invade into the queenside if even stockfish struggles with that?
Seemingly not difficult at all. Bring the king to g4, bishop to e2, so that it helps molesting the king later and then create the double threat of either invading queen side or king side.
E.g. from this position, my stockfish already shows double digit advantage for black:
[d]8/8/p5p1/1p3k2/1P6/P3KpB1/4b3/8 b - - 11 6
Top
User avatar
Eelco de Groot
Posts: 4565
Joined: Sun Mar 12, 2006 2:40 am
Full name:   

Re: Testposition Opposite coloured Bishops

Post by Eelco de Groot »

Hi Lyudmil,

Yes I agree, to a human eye it looks terrible for White, especially if you don't yet know about the opposite colour bishops. But Stockfish's rule is rather simple, possibly too simple.
Taking into acount the weak pawns in presence of opp coloured bishops is not going to be very easy probably because that is decided (well at least in the sense of a3 being a backward pawn) in pawns.cpp but you don't even know where the king is when you are there. It seemed to me a rule with passed pawns would at least help and that information is readily available in evaluate.cpp.

Added difficulty is that the process involves Zugzwang (I have not really verified how much, and how bad Null move is here). If you lower all the scores for White with the proposed change in eval, it also means that finding a drawscore with c6 (I also did not really test whether that is the only draw possibility but it seems to work), in practice you can find 1. c6 in Ma Laoshi's position, but Serpent only gives it -3 now. You detect it because all the other scores are even lower. But the low -3 can also potentially be a problem because Black might think he is winning this in earlier positions for instance.. In many lines it's true but there might be the odd drawing line, like c6, and that does not get anything close to 0.0 yet.
Debugging is twice as hard as writing the code in the first
place. Therefore, if you write the code as cleverly as possible, you
are, by definition, not smart enough to debug it.
-- Brian W. Kernighan
Top
User avatar
Eelco de Groot
Posts: 4565
Joined: Sun Mar 12, 2006 2:40 am
Full name:   

Re: Testposition Opposite coloured Bishops

Post by Eelco de Groot »

Hi Oliver,

Yes, I think it must be won, I got low -4 scores in fact a bit faster when I had not changed eval. The eval change seems to help much more in positions nearer the original (Laoshi's Nunn position) and here in lower plies, but not in finding the actual win, in this position.

Without any eval change (that is 016), but already here with a slight change to null move verification, see scores below. I assume this is more like Stockfish would score it. Serpent actually just does Null move even in pawn only endgames, so that is much more risky than Stockfish itself does it, but it does do a verification search instead even at low depths below 12 ply in that case. But R (the reduction factor) is usually high, higher than Stock.

[D]8/2B5/p1b3p1/1p3k2/1P6/P4p2/5K2/8 w - -

Engine: Rainbow Serpent 20160903_015 HT (512 MB)
by T. Romstad, M. Costalba, J. Kiiski, G. Linscott

33/45 0:03 -1.50++ 10.Ke3 (59.809.248) 16453

33/45 0:03 -1.32 10.Ke3 g5 11.Bg3 g4 12.Kd3 Bd7
13.Ke3 Ke6 14.Ke4 Kf6 15.Kd4 Be6
16.Ke3 Kg5 17.Kf2 Bf7 18.Ke3 Kf5
19.Kd3 Be6 20.Ke3 Bd5 21.Kd4 Bc4
22.Ke3 Kg5 23.Kf2 (64.860.077) 16550

34/45 0:04 -1.32 10.Ke3 g5 11.Bg3 g4 12.Kd3 Bd5
13.Kd4 Bc4 14.Ke3 Bf7 15.Kd3 Be6
16.Ke3 Kg5 17.Kf2 Bc4 18.Bd6 Kh4
19.Be5 Be6 20.Bg3+ Kg5 21.Bd6 Kf5
22.Ke3 Bd5 23.Bg3 (72.418.668) 16628

35/45 0:04 -1.32 10.Ke3 g5 11.Bg3 g4 12.Kd3 Bd5
13.Kd4 Bc4 14.Ke3 Bf7 15.Kd3 Be6
16.Ke3 Kg5 17.Kf2 Bc4 18.Bd6 Kh4
19.Be5 Be6 20.Bg3+ Kg5 21.Ke3 Kf5
22.Kd3 Ba2 23.Ke3 (75.742.020) 16675

36/45 0:05 -1.32 10.Ke3 g5 11.Bg3 g4 12.Kd3 Ke6
13.Kd4 Bb7 14.Bf2 Kf5 15.Bg3 Kg5
16.Kd3 Bd5 17.Kd4 Bc6 18.Ke3 Bd7
19.Kf2 Bf5 20.Be5 Kh5 21.Bd6 Kh4
22.Bc7 Kh3 23.Bf4 (88.364.197) 16745

37/45 0:06 -1.32 10.Ke3 g5 11.Bg3 g4 12.Kd3 Bd5
13.Kd4 Bc4 14.Ke3 Bf7 15.Kd3 Be6
16.Ke3 Kg5 17.Kf2 Bc4 18.Bd6 Kf5
19.Ke3 Bf7 20.Bg3 Be6 21.Bd6 Bb3
22.Bg3 Kg5 23.Kf2 (100.786.298) 16789

38/45 0:07 -1.32 10.Ke3 g5 11.Bg3 g4 12.Kd3 Bd5
13.Kd4 Bc4 14.Ke3 Bf7 15.Kd3 Be6
16.Ke3 Kg5 17.Kf2 Bc4 18.Bd6 Kh4
19.Be5 Be6 20.Bg3+ Kg5 21.Bd6 Kf6
22.Bg3 Bc4 23.Ke3 (124.539.932) 16816

39/45 0:08 -1.32 10.Ke3 g5 11.Bg3 g4 12.Kd3 Bd5
13.Kd4 Bc4 14.Ke3 Bf7 15.Kd3 Be6
16.Ke3 Kg5 17.Kf2 Bc4 18.Bd6 Kh4
19.Be5 Be6 20.Bg3+ Kg5 21.Ke3 Bf7
22.Bf4+ Kh4 23.Kf2 (143.603.128) 16904

40/45 0:10 -1.32 10.Ke3 g5 11.Bg3 g4 12.Kd3 Bd5
13.Kd4 Bc4 14.Ke3 Bf7 15.Kd3 Be6
16.Ke3 Kg5 17.Kf2 Bc4 18.Bd6 Kh4
19.Be5 Be6 20.Bg3+ Kg5 21.Ke3 Bd5
22.Kd3 Bb3 23.Ke4 (172.560.065) 17037

41/45 0:13 -1.32 10.Ke3 g5 11.Bg3 g4 12.Kd3 Bd5
13.Kd4 Bc4 14.Ke3 Bf7 15.Kd3 Be6
16.Ke3 Bd7 17.Kd3 Be8 18.Ke3 Kf6
19.Kf4 Bd7 20.Bf2 Kf7 21.Bg3 Be6
22.Ke3 Kg6 23.Kf2 (226.411.971) 16973

42/49 0:19 -1.40-- 10.Ke3 g5 (316.828.484) 16638

42/49 0:25 -1.48-- 10.Ke3 g5 (415.075.025) 16524

42/52 1:13 -1.51 10.Ke3 g5 11.Bd6 Kf6 12.Bb8 Bb7
13.Bg3 Kg6 14.Kf2 Kf5 15.Ke3 Bd5
16.Bh2 Ba8 17.Bg3 Ke6 18.Kd4 Bb7
19.Ke3 Kf6 20.Kf2 Ke7 21.Ke3 Ke6
22.Kd4 Ba8 23.Ke3 (1.193.053.203) 16331

43/52 1:26 -1.51 10.Ke3 g5 11.Bd6 Ke6 12.Bg3 Bd5
13.Bc7 Kf5 14.Bg3 Bb7 15.Bc7 Kf6
16.Bd8+ Kg6 17.Bc7 Bd5 18.Kf2 Kf6
19.Bg3 Bc6 20.Ke3 Ba8 21.Bf2 Bd5
22.Bg3 Bb7 23.Bd6 (1.410.067.706) 16340

44/52 1:55 -1.59-- 10.Ke3 g5 (1.909.090.795) 16467

44/52 2:08 -1.67-- 10.Ke3 g5 (2.114.267.458) 16438

44/52 2:27 -1.79-- 10.Ke3 g5 (2.419.996.655) 16444

44/52 2:37 -1.96-- 10.Ke3 g5 (2.591.154.192) 16413

44/52 3:31 -2.19-- 10.Ke3 g5 (3.450.176.266) 16318

44/52 5:09 -2.19 10.Ke3 g5 11.Bh2 Bb7 12.Bc7 Kg4
13.Bd6 Bd5 14.Bb8 Bc4 15.Bc7 Be2
16.Bd6 Bd1 17.Bc7 Kf5 18.Bg3 Be2
19.Bc7 Ke6 20.Bb6 Kd5 21.Kf2 Kc4
22.Bd8 g4 23.Bf6 (5.355.494.554) 17289

45/52 5:50 -2.27-- 10.Ke3 Bd5 (6.044.624.286) 17245

45/52 6:22 -2.35-- 10.Ke3 Bd5 (6.600.344.076) 17262

45/52 6:34 -2.47-- 10.Ke3 Bd5 (6.792.408.561) 17214

45/52 8:39 -2.64-- 10.Ke3 Bd5 (8.918.198.817) 17154

45/52 11:12 -2.87-- 10.Ke3 Bd5 (11.562.891.134) 17199

45/62 13:46 -3.18-- 10.Ke3 g5 (14.185.267.810) 17171

45/62 17:08 -3.58-- 10.Ke3 g5 (17.560.300.145) 17077

45/62 23:47 -4.10-- 10.Ke3 Bd5 (24.372.408.612) 17068

45/62 26:13 -4.78-- 10.Ke3 Bd5 (26.668.269.434) 16950

45/62 28:49 -4.95 10.Ke3 Bd5 11.Bb8 Kg4 12.Kf2 Bb3
13.Ba7 Bd1 14.Be3 Kf5 15.Bb6 Kf4
16.Ba5 Kg4 17.Bb6 Be2 18.Bc5 Kf4
19.Bd6+ Kf5 20.Bb8 Ke4 21.Kg1 Bd1
22.Kh2 Ke3 23.Kg3 (29.126.844.723) 16845

46/63 30:29 -4.96 10.Ke3 Bd5 11.Bb8 Kg4 12.Bd6 Bc4
13.Be5 Be2 14.Bd6 Kf5 15.Kd2 g5
16.Ke3 Ke6 17.Bg3 Kd5 18.Bb8 g4
19.Bf4 Kc4 20.Bc7 Bd3 21.Ba5 Bf1
22.Kf2 Be2 23.Bb6 (30.676.362.556) 16767

47/63 33:26 -5.04 10.Ke3 Bd5 11.Bb8 Kg4 12.Kf2 Bb3
13.Ba7 Bd1 14.Be3 Kf5 15.Bb6 Kf4
16.Ba5 Be2 17.Bb6 Ke4 18.Bd8 Kd3
19.Be7 Kd4 20.Bc5+ Kd5 21.Ke1 g5
22.Kd2 Ke4 23.Ba7 (33.404.700.857) 16649

48/63 35:31 -5.12-- 10.Ke3 Bd5 (35.300.769.537) 16562

48/63 37:27 -5.12 10.Ke3 Bd5 11.Bb8 Kg5 12.Bg3 Kg4
13.Kf2 Bb3 14.Bh2 Bc4 15.Bd6 Be2
16.Bh2 Bd1 17.Kf1 Kf5 18.Ke1 Be2
19.Kf2 Ke4 20.Bg1 Kd4 21.Ke1+ Kc3
22.Bf2 Kb3 23.Bb6 (37.176.406.467) 16544

49/63 38:46 -5.12 10.Ke3 Bd5 11.Bb8 Kg5 12.Bg3 Kg4
13.Kf2 Bb3 14.Bh2 Bc4 15.Bd6 Be2
16.Bh2 Bd1 17.Kf1 Kf5 18.Ke1 Be2
19.Bd6 Ke4 20.Kd2 Bc4 21.Ke1 Bd3
22.Bc5 Kf4 23.Kf2 (38.516.674.311) 16558

50/63 44:29 -5.20-- 10.Ke3 Bd5 (44.121.172.583) 16528

50/66 47:22 -5.28-- 10.Ke3 Bd5 (46.848.491.761) 16483

50/68 52:17 -5.40-- 10.Ke3 Bd5 (51.439.830.061) 16394

50/68 54:49 -5.57-- 10.Ke3 Bd5 (53.748.352.255) 16338

best move: Kf2-e3 time: 55:57.656 min n/s: 16.338.633 nodes: 54.786.687.770
Debugging is twice as hard as writing the code in the first
place. Therefore, if you write the code as cleverly as possible, you
are, by definition, not smart enough to debug it.
-- Brian W. Kernighan
Top
User avatar
Eelco de Groot
Posts: 4565
Joined: Sun Mar 12, 2006 2:40 am
Full name:   

Re: Testposition Opposite coloured Bishops

Post by Eelco de Groot »

Paloma wrote:Why is the white pawn on c5 disappeared :?:
Hi Herbert, Sorry I did not give the line because it is not going to be anywhere correct, because Serpent was playing blind, he thinks everything is still almost a draw. But even when he does not give the c5 pawn away on the first move, he does so a little later. Presumably too late but I did not really test all that. I just wondered how long it would take to see that he is lost, playing blind, here we are ten moves from the starting position and it still takes a long time to see (output above from version 015 for instance).
Debugging is twice as hard as writing the code in the first
place. Therefore, if you write the code as cleverly as possible, you
are, by definition, not smart enough to debug it.
-- Brian W. Kernighan
Top
peter
Posts: 3186
Joined: Sat Feb 16, 2008 7:38 am
Full name: Peter Martan

Re: Testposition Opposite coloured Bishops

Post by peter »

Hi Eelco!
Eelco de Groot wrote: The eval change seems to help much more in positions nearer the original (Laoshi's Nunn position) and here in lower plies, but not in finding the actual win, in this position.
From the chessprogramming Wikispaces- link to Sune Larssons testsuite of Nunn- endgame- postions on this site
http://www.stmintz.com/ccc/index.php?id=476109
, it's number 7 with this description:

[Event "Larsson"]
[Site "Endgame Test"]
[Date "1970.??.??"]
[Round "?"]
[White "Larsson 07"]
[Black "?"]
[Result "*"]
[Annotator "GM Nunn"]
[SetUp "1"]
[FEN "8/8/p4Bp1/1pPb2P1/1P2kp2/P7/5K2/8 w - - 0 1"]
[PlyCount "0"]
[EventDate "2005.??.??"]

{{Bellon-Minic, Siegen 1970. A fantastic position. An opposite-coloured bishop
position with equal pawns looks as if it should be a draw, and indeed the
players agreed to a draw at this point. However, White has serious problems
because of his weak a3-pawn, which cannot be permanently defended by his
bishop. Once this pawn has been captured, Black has the chance to make a
second passed pawn by playing ...a5, which will stretch White's defence to the
utmost. Dvoretsky and Yusupov subjected this ending to detailed analysis, and
came to the astonishing conclusion that it is a draw, but only if White
starts with the incredible 1 c6!!. It is hard to imagine that any machine
would find such a move, but who knows what might happen in the future...}
Peter.
Top
Lyudmil Tsvetkov
Posts: 6052
Joined: Tue Jun 12, 2012 12:41 pm

Re: Testposition Opposite coloured Bishops

Post by Lyudmil Tsvetkov »

does not black win much easier after Ke3 Ke6 (aiming for d5) Kd4 g5 ?
Top
peter
Posts: 3186
Joined: Sat Feb 16, 2008 7:38 am
Full name: Peter Martan

Re: Testposition Opposite coloured Bishops

Post by peter »

The position I am and was talking about in my previous posting ist not the one, Eelco came up with, a few moves later along an already lost line. Engines don't really have a chance to see 1.c6!! building a fortress because of the differently coloured Bishops, being blind for fortresses still, so Eelco wanted to know, if they'd be able to see the White loss at least some moves after the missed chance for the fortress- building.
Here is the original Nunn test position again:
[D]8/8/p4Bp1/1pPb2P1/1P2kp2/P7/5K2/8 w - - 0 1
Taken from Belon-Minic 1/2-1/2, Siegen 1970
Peter.
Top

Return to “Computer Chess Club: General Topics”