Topic Rybka Support & Discussion / Rybka Discussion / Another tough test for Rybka (she misses a mating line)
![[it]](/mwf/v12/flags/it.png "Italy")
Hi, Vas. I'm still going on to post here critical positions, hoping to help you in improving Rybka. IMO, this example shows a serious tactical blind spot.
Andrew Martin's problems appear to be a very hard task to Rybka: this is the second time (out of his last three) that Rybka can't find the right solution.
http://www.chessbase.com/newsdetail.asp?newsid=3773
white to move and win.
Many engines (toga II 3x4, fritz10, gambitfruit, Shredder10, naum2.0...) find the right 1.Bc6 between 12-16 ply, with eval between +8 ,+14.
BUT:
Analysis by Rybka 2.3.1 32-bit 20pl :
1. = (0.00): 1.Kd2 g2 2.Qe1 Rd4+ 3.Kc3 g1Q 4.Qh4+ Kg2 5.Bc6+ Kf1 6.Bb5+ Kg2 7.Bc6+ Kf1
2. ³ (-0.37): 1.Bc6 Rb1+ 2.Ke2 Rxh1 3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Bc6 Bc5 7.Kf1 Bd6
Apparently correct: But, let's force 1.Bc6 , in order to look at this discrepant evaluation:
Analysis by Rybka 2.3.1 32-bit after 1.Bc6:
1. ³ (-0.33): 1...Rb1+ 2.Ke2 Rxh1 3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Kd3 Bb2 7.Ne6 Kh5 8.Nf4+
2. +- (+14.86): 1...Rb2 2.Bg2+ Rxg2 3.Nf4+ Kh4 4.Qxg2 Kg5 5.Qd2 g2 6.Nxg2+ f4 7.Qd8+ Kf5 8.Qd7+ Kg5 9.Qg7+ Kf5 10.Qh7+ Ke5
Good Grief! line 1 misses a forced white mate line: not 3.Nf4+(??), but 3.Bg2+!!, with continuation 4.Nf4+ Kg1 5.Ke1 g2 6.Ne2#
Andrew Martin's problems appear to be a very hard task to Rybka: this is the second time (out of his last three) that Rybka can't find the right solution.
http://www.chessbase.com/newsdetail.asp?newsid=3773
4B3/8/6N1/5p2/1r4p1/6pk/7b/4K2Q w - - 0 1
white to move and win.
Many engines (toga II 3x4, fritz10, gambitfruit, Shredder10, naum2.0...) find the right 1.Bc6 between 12-16 ply, with eval between +8 ,+14.
BUT:
Analysis by Rybka 2.3.1 32-bit 20pl :
1. = (0.00): 1.Kd2 g2 2.Qe1 Rd4+ 3.Kc3 g1Q 4.Qh4+ Kg2 5.Bc6+ Kf1 6.Bb5+ Kg2 7.Bc6+ Kf1
2. ³ (-0.37): 1.Bc6 Rb1+ 2.Ke2 Rxh1 3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Bc6 Bc5 7.Kf1 Bd6
Apparently correct: But, let's force 1.Bc6 , in order to look at this discrepant evaluation:
Analysis by Rybka 2.3.1 32-bit after 1.Bc6:
1. ³ (-0.33): 1...Rb1+ 2.Ke2 Rxh1 3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Kd3 Bb2 7.Ne6 Kh5 8.Nf4+
2. +- (+14.86): 1...Rb2 2.Bg2+ Rxg2 3.Nf4+ Kh4 4.Qxg2 Kg5 5.Qd2 g2 6.Nxg2+ f4 7.Qd8+ Kf5 8.Qd7+ Kg5 9.Qg7+ Kf5 10.Qh7+ Ke5
Good Grief! line 1 misses a forced white mate line: not 3.Nf4+(??), but 3.Bg2+!!, with continuation 4.Nf4+ Kg1 5.Ke1 g2 6.Ne2#
![[de]](/mwf/v12/flags/de.png "Germany")
There is no interest in such positions yet. None version of Rybka can solve this. The zugzwang issue will be treated later as Vas said.
![[us]](/mwf/v12/flags/us.png "United States")
Seems almost comical that Rybka doesn't see Bg2. To the human it looks obvious.
![[il]](/mwf/v12/flags/il.png "Israel")
I think that it is dependent on the human.
I am sure that for many humans taking the rook seems obvious because usually in games you take pieces and not sacrifice.
When you know that it is a study the situation is different but rybka does not know that it is a study.
Uri
I am sure that for many humans taking the rook seems obvious because usually in games you take pieces and not sacrifice.
When you know that it is a study the situation is different but rybka does not know that it is a study.
Uri
Good point
I disgaree.
The zugzwang issue is an important one because there are practical positions when it is impossible to win by other means.
Toga has no problem to see it so null move pruning is not a good reason to ignore zugzwangs.
Uri
The zugzwang issue is an important one because there are practical positions when it is impossible to win by other means.
Toga has no problem to see it so null move pruning is not a good reason to ignore zugzwangs.
Uri
No, IMO it is not the zugzwang position here that causes Rybka to fail.
Look at it: let us slide forward to the point where rybka fails, missing the mating line: the zugzwang is still identical, but:
single analysis line:
3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Ne6 Bb6 7.Kd3 Kh5 8.Bc6 Kg6 9.Ke2 Kf6
³ (-0.34) Depth: 20 00:00:16 1613kN, tb=32
2 analysis lines:
Analysis by Rybka 2.3.1 32-bit : depth 20
1. ³ (-0.36): 3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Kd3 Bb2 7.Kd2 Kg5 8.Ne6+ Kh5 9.Kc2 Be5
2. ³ (-0.63): 3.Bxh1 g2 4.Bxg2+ Kxg2 5.Nh4+ Kh3 6.Nxf5 Bf4 7.Kf1 Bc7 8.Ke2 Bb6 9.Kd3 Bd8
3 analysis lines:
Analysis by Rybka 2.3.1 32-bit depth 15:
1. +- (#4): 3.Bg2+ Kxg2 4.Nf4+ Kg1 5.Ke1
2. ³ (-0.33): 3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Kd3 Bb2 7.Kd2 Kg5 8.Ne6+ Kf6 9.Nf4 Ba3
3. ³ (-0.55): 3.Bxh1 g2 4.Bxg2+ Kxg2 5.Nh4+ Kh3 6.Nxf5 Bg1 7.Ne7 Bd4 8.Nf5 Bc5 9.Kd3 Bb6
The problem seems related to insufficient number of search lines.
Look at it: let us slide forward to the point where rybka fails, missing the mating line: the zugzwang is still identical, but:
8/8/2B3N1/5p2/6p1/6pk/4K2b/7r w - - 0 1
single analysis line:
3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Ne6 Bb6 7.Kd3 Kh5 8.Bc6 Kg6 9.Ke2 Kf6
³ (-0.34) Depth: 20 00:00:16 1613kN, tb=32
2 analysis lines:
Analysis by Rybka 2.3.1 32-bit : depth 20
1. ³ (-0.36): 3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Kd3 Bb2 7.Kd2 Kg5 8.Ne6+ Kh5 9.Kc2 Be5
2. ³ (-0.63): 3.Bxh1 g2 4.Bxg2+ Kxg2 5.Nh4+ Kh3 6.Nxf5 Bf4 7.Kf1 Bc7 8.Ke2 Bb6 9.Kd3 Bd8
3 analysis lines:
Analysis by Rybka 2.3.1 32-bit depth 15:
1. +- (#4): 3.Bg2+ Kxg2 4.Nf4+ Kg1 5.Ke1
2. ³ (-0.33): 3.Nf4+ Kh4 4.Bxh1 Bg1 5.Bg2 Bd4 6.Kd3 Bb2 7.Kd2 Kg5 8.Ne6+ Kf6 9.Nf4 Ba3
3. ³ (-0.55): 3.Bxh1 g2 4.Bxg2+ Kxg2 5.Nh4+ Kh3 6.Nxf5 Bg1 7.Ne7 Bd4 8.Nf5 Bc5 9.Kd3 Bb6
The problem seems related to insufficient number of search lines.
No
It is the zugzwang position that cause rybka to fail.
I guess that with more lines it finds the right score for 3.Bg2+ simply because in this condition 5.Ke1 has a threat.
threat is a relative thing and I guess that 5.Ke1 is analyzed if rybka finds that 5.Ke1 threats something better than the score of the third best move.
It is the zugzwang position that cause rybka to fail.
I guess that with more lines it finds the right score for 3.Bg2+ simply because in this condition 5.Ke1 has a threat.
threat is a relative thing and I guess that 5.Ke1 is analyzed if rybka finds that 5.Ke1 threats something better than the score of the third best move.
The instant you play Bg2 it sees the mate, I mean the INSTANT; all multi variation mode does is force the engine to look at it, because it's the third best move. (other moves quickly lose)
The zugzwang after Ke1 seems to be where Rybka (and some others) fails, Ne2 isn't threatening anything yet until black plays the only move ...g2.
I'm looking at this position with Winfinder now and getting some truly strange results. For instance in the positions leading up to the mate it shows the correct mate numbers but the lines all stop after Ke1. In fact in the position after 5.Ke1 Winfinder 2.2 32-bit shows 1. +-(#16):5...g2 6. Ne2#
It's clearly this zugzwang issue that is driving Rybka mad but it's hard to understand here with mate so close, at least this functionality should be in Winfinder. It's clearly a place where the product needs some polish.
The zugzwang after Ke1 seems to be where Rybka (and some others) fails, Ne2 isn't threatening anything yet until black plays the only move ...g2.
I'm looking at this position with Winfinder now and getting some truly strange results. For instance in the positions leading up to the mate it shows the correct mate numbers but the lines all stop after Ke1. In fact in the position after 5.Ke1 Winfinder 2.2 32-bit shows 1. +-(#16):5...g2 6. Ne2#
It's clearly this zugzwang issue that is driving Rybka mad but it's hard to understand here with mate so close, at least this functionality should be in Winfinder. It's clearly a place where the product needs some polish.
![[pl]](/mwf/v12/flags/pl.png "Poland")
Analysis by Rybka 2.3.1 mp 32-bit :
1.Bc6
+- (6.56) Depth: 2 00:00:00
1.Bc6
+- (7.32) Depth: 3 00:00:00
1.Bc6
+- (7.54) Depth: 4 00:00:00
1.Bc6 Rb2+ 2.Ke3
+- (7.89) Depth: 5 00:00:00
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4
+- (7.54) Depth: 6 00:00:00 4kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2
+- (8.43) Depth: 7 00:00:00 6kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Qxg2
+- (7.78) Depth: 8 00:00:00 7kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Nxg2+ Kg5 7.Qc1+ Kf6
+- (9.02) Depth: 9 00:00:00 14kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Nxg2+ Kg5 7.Qc1+ Kf6
+- (9.48) Depth: 10 00:00:00 24kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Bg1+ 5.Qxg1 g2 6.Nf4+ Kh4 7.Nxg2+ Kg3
+- (11.03) Depth: 11 00:00:01 93kN, tb=1
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Bf4 7.Nxf4+ Kg3
+- (12.21) Depth: 12 00:00:01 174kN, tb=2
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Rb5+ 7.Bxb5 g1Q
+- (14.57) Depth: 13 00:00:03 309kN, tb=4
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Bf4 7.Nxf4+ Kg3
+- (18.31) Depth: 14 00:00:05 544kN, tb=22
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Rb5+ 7.Bxb5 g1Q 8.Bf1+ Qxf1+ 9.Qxf1+ Kg3 10.Nf4 Kh4 11.Qg2 Bg3 12.Qh1+ Bh2 13.Qxh2#
+- (#13) Depth: 15 00:00:07 577kN, tb=65
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Rb5+ 7.Bxb5 g1Q 8.Bf1+ Qxf1+ 9.Qxf1+ Kg3 10.Nf4 Kh4 11.Qg2 Bg3 12.Qh1+ Bh2 13.Qxh2#
+- (#12) Depth: 16 00:00:09 628kN, tb=191
And without TB:
1.Bc6
+- (6.56) Depth: 2 00:00:00
1.Bc6
+- (7.32) Depth: 3 00:00:00
1.Bc6
+- (7.54) Depth: 4 00:00:00
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4
+- (7.54) Depth: 5 00:00:00
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4
+- (7.54) Depth: 7 00:00:00 6kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2
+- (8.43) Depth: 7 00:00:00 6kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Qxg2
+- (7.78) Depth: 8 00:00:00 7kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Nxg2+ Kg5 7.Qc1+ Kf6
+- (9.02) Depth: 9 00:00:00 13kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Nxg2+ Kg5 7.Qc1+ Kf6
+- (9.60) Depth: 10 00:00:00 28kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Nxg2+ Kg5 6.Qd1 Kf6 7.Kf4 Ke6
+- (7.10) Depth: 11 00:00:00 88kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Nxg2+ Kg5 6.Qd1 Kf6 7.Kf4 Ke6
+- (9.46) Depth: 11 00:00:01 104kN
1.Bc6 Rb2+ 2.Ke3 Ra2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Nxg2+ Kg5 6.Qa1 f4+ 7.Nxf4 Kf5
+- (5.12) Depth: 12 00:00:02 230kN
1.Bc6 Rb2+ 2.Ke3 Ra2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Nxg2+ Kg5 6.Qa1 f4+ 7.Nxf4 Kf5
+- (10.65) Depth: 12 00:00:02 238kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4
+- (13.61) Depth: 13 00:00:02 298kN
1.Bc6 Rb2+ 2.Ke3 Ra2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4
+- (14.86) Depth: 14 00:00:03 382kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4
+- (15.23) Depth: 15 00:00:04 521kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4 8.Qxd4 g2 9.Nxg2+ Kh3 10.Nf4+ Kg3 11.Ne2+ Kh4 12.Qh8+ Kg5 13.Qg7+ Kh5 14.Ng3+ Kh4 15.Nxf5+ Kh3 16.Ke4 Kg2
+- (#22) Depth: 16 00:00:07 991kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4 8.Qxd4 g2 9.Qf6+ Kg3 10.Ne2+ Kf2 11.Qd4+ Kf1 12.Qg1#
+- (#12) Depth: 17 00:00:08 1026kN
1.Bc6
+- (6.56) Depth: 2 00:00:00
1.Bc6
+- (7.32) Depth: 3 00:00:00
1.Bc6
+- (7.54) Depth: 4 00:00:00
1.Bc6 Rb2+ 2.Ke3
+- (7.89) Depth: 5 00:00:00
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4
+- (7.54) Depth: 6 00:00:00 4kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2
+- (8.43) Depth: 7 00:00:00 6kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Qxg2
+- (7.78) Depth: 8 00:00:00 7kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Nxg2+ Kg5 7.Qc1+ Kf6
+- (9.02) Depth: 9 00:00:00 14kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Nxg2+ Kg5 7.Qc1+ Kf6
+- (9.48) Depth: 10 00:00:00 24kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Bg1+ 5.Qxg1 g2 6.Nf4+ Kh4 7.Nxg2+ Kg3
+- (11.03) Depth: 11 00:00:01 93kN, tb=1
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Bf4 7.Nxf4+ Kg3
+- (12.21) Depth: 12 00:00:01 174kN, tb=2
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Rb5+ 7.Bxb5 g1Q
+- (14.57) Depth: 13 00:00:03 309kN, tb=4
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Bf4 7.Nxf4+ Kg3
+- (18.31) Depth: 14 00:00:05 544kN, tb=22
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Rb5+ 7.Bxb5 g1Q 8.Bf1+ Qxf1+ 9.Qxf1+ Kg3 10.Nf4 Kh4 11.Qg2 Bg3 12.Qh1+ Bh2 13.Qxh2#
+- (#13) Depth: 15 00:00:07 577kN, tb=65
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Qc1 Rb4+ 5.Ke5 g2+ 6.Kxf5 Rb5+ 7.Bxb5 g1Q 8.Bf1+ Qxf1+ 9.Qxf1+ Kg3 10.Nf4 Kh4 11.Qg2 Bg3 12.Qh1+ Bh2 13.Qxh2#
+- (#12) Depth: 16 00:00:09 628kN, tb=191
And without TB:
1.Bc6
+- (6.56) Depth: 2 00:00:00
1.Bc6
+- (7.32) Depth: 3 00:00:00
1.Bc6
+- (7.54) Depth: 4 00:00:00
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4
+- (7.54) Depth: 5 00:00:00
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4
+- (7.54) Depth: 7 00:00:00 6kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2
+- (8.43) Depth: 7 00:00:00 6kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Qxg2
+- (7.78) Depth: 8 00:00:00 7kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Nxg2+ Kg5 7.Qc1+ Kf6
+- (9.02) Depth: 9 00:00:00 13kN
1.Bc6 Rb2+ 2.Ke3 Rb3+ 3.Kd4 Rb2 4.Bg2+ Rxg2 5.Nf4+ Kh4 6.Nxg2+ Kg5 7.Qc1+ Kf6
+- (9.60) Depth: 10 00:00:00 28kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Nxg2+ Kg5 6.Qd1 Kf6 7.Kf4 Ke6
+- (7.10) Depth: 11 00:00:00 88kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Nxg2+ Kg5 6.Qd1 Kf6 7.Kf4 Ke6
+- (9.46) Depth: 11 00:00:01 104kN
1.Bc6 Rb2+ 2.Ke3 Ra2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Nxg2+ Kg5 6.Qa1 f4+ 7.Nxf4 Kf5
+- (5.12) Depth: 12 00:00:02 230kN
1.Bc6 Rb2+ 2.Ke3 Ra2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Nxg2+ Kg5 6.Qa1 f4+ 7.Nxf4 Kf5
+- (10.65) Depth: 12 00:00:02 238kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4
+- (13.61) Depth: 13 00:00:02 298kN
1.Bc6 Rb2+ 2.Ke3 Ra2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4
+- (14.86) Depth: 14 00:00:03 382kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4
+- (15.23) Depth: 15 00:00:04 521kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4 8.Qxd4 g2 9.Nxg2+ Kh3 10.Nf4+ Kg3 11.Ne2+ Kh4 12.Qh8+ Kg5 13.Qg7+ Kh5 14.Ng3+ Kh4 15.Nxf5+ Kh3 16.Ke4 Kg2
+- (#22) Depth: 16 00:00:07 991kN
1.Bc6 Rb2+ 2.Ke3 Rc2 3.Bg2+ Rxg2 4.Nf4+ Kh4 5.Qa1 Bg1+ 6.Kd3 Rb2 7.Qxb2 Bd4 8.Qxd4 g2 9.Qf6+ Kg3 10.Ne2+ Kf2 11.Qd4+ Kf1 12.Qg1#
+- (#12) Depth: 17 00:00:08 1026kN
You have the position wrong, it's not possible to play 2. Ke3. (and 1...Rb2 isn't check)
![[hu]](/mwf/v12/flags/hu.png "Hungary")
This is a zugzwang issue. After 1. Bc6 Rb1+ 2. Ke2 Rxh1 3. Bg2+ Kxg2 4. Nf4+ Kg1 5. Ke1 black is in a very bizarre zugzwang.
Vas
Vas
It seems to be a hard problem. Even A.M. ,
http://www.chessbase.com/newsdetail.asp?newsid=3783
after showing the best line 1.Bc6, gives as alternative 1.Qd5 or 1.Nf4, and not the drawish Kd2.
http://www.chessbase.com/newsdetail.asp?newsid=3783
after showing the best line 1.Bc6, gives as alternative 1.Qd5 or 1.Nf4, and not the drawish Kd2.
Topic Rybka Support & Discussion / Rybka Discussion / Another tough test for Rybka (she misses a mating line)
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