Defence vs. Attack

[tpoppins]

In November 2015 I posted on chessgames.com some detailed analysis on the ramification of the 24.Qxe5 queen sacrifice. This was just the tip of the iceberg of the much more extensive (over 12 hours) analysis I had to perform to get convincing (high eval at high depth) entries on Let's Check in dozens of variations that emanate from that position.

The engine I used at the time was Houdini 4 Pro in Tactical Mode with a 32 GB hash. In 2016 I was able to replicate the results with an April 2016 SF dev build and later with Komodo 9.2 and 10.1. In October I went through the whole thing yet again with the then-current CorChess (SF fork tuned for LTC) version and then, with all the backward-sliding analysis still in the hash, let it sit for over 15 hours on the root position to generate a top entry with sufficient depth (68) to deter casual patzers from overwriting it in the foreseeable future. For comparison Louis Zulli (where the hell is he, BTW?) went "only" to d=52 in April 2015.

Good thing, too, because last month the entries ##2 and 3 were overwritten with 24.Qa3 courtesy of recent SF dev builds, complete with 0.00 evals. I won't name the user who did that as he's a long-time poster here who certainly should know better (seeing how the 2015 posts on Chessgames back-linked to a long thread about this position here) and at least had enough sense (or not enough patience ;) not to overwrite the top d=68 entry. Another of our posters here (one of the most prolific ones) "contributed" a -0.38 entry for the position after 24.Qxe5 only yesterday. Ugh ... looks like I'll have to set a whole day aside for going in there and cleaning up the mess ... yet again. Now you can see why my nym on Chessbase is Never_Again, heh.

Now to Bernhard's question - does 29...cxb3 (not 29...bxc3 - illegal and sloppy, sorry, Bernhard) draw? Perhaps it does, but the question is irrelevant because two moves earlier White has a crucial improvement in 28.a4! I refer you to the third part of the above-mentioned analysis on Chessgames for details.

The bottom line is that after 24.Qxe5 White wins in all variations. The only engines that could crack this position in reasonable amount of time that I am aware of were Sting 6 and Houdini 4 Pro in Tactical mode. The latter did it just once and I wasn't able to reproduce that fluke (no log either, sorry). Komodo with null-move pruning turned off can also do it but takes considerably longer. Finally, vanilla SF may be able to do it in Multi-PV=x (where x should probably be at least 12) but that would probably take days.

Some excerpts from the analysis logs in my archives:

[d]4q1kr/p6p/1prQPppB/4n3/4P3/2P5/PP2B2P/R5K1 w - - 0 24
Yuri S Gusev - E Auerbach, Molniya Sporting Society 1946

Code: Select all

Analysis by Sting SF 6 64bit:

1.Qa3 
  =/+  (-0.48 --)   Depth: 7   00:00:04  7kN
1.Qa3 
  =  (-0.24 ++)   Depth: 7   00:00:04  8kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bd2 Rxe4 4.Bf3 
  =  (-0.16)   Depth: 7   00:00:04  8kN
1.Qa3 
  =  (-0.28 --)   Depth: 8   00:00:04  11kN
1.Qa3 
  =/+  (-0.40 --)   Depth: 8   00:00:04  14kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bd2 Kg7 4.Rf1 Qe7 5.Qxe7 Rxe7 
  =/+  (-0.44)   Depth: 8   00:00:04  16kN
1.Qa3 
  =/+  (-0.56 --)   Depth: 9   00:00:04  23kN
1.Qd5 
  =/+  (-0.32 ++)   Depth: 9   00:00:04  27kN
1.Qd5 
  =  (-0.14 ++)   Depth: 9   00:00:04  29kN
1.Qd5 
  =  (0.14 ++)   Depth: 9   00:00:04  30kN
1.Qd5 Rxe6 2.Bb5 Qc8 3.Kg2 g5 4.Rd1 Kf7 5.h4 Kg6 
  =/+  (-0.44)   Depth: 9   00:00:04  48kN
1.Qd5 
  =/+  (-0.56 --)   Depth: 10   00:00:04  70kN
1.Qb4 
  =/+  (-0.32 ++)   Depth: 10   00:00:04  101kN
1.Qb4 
  =/+  (-0.68 --)   Depth: 10   00:00:04  123kN
1.Qb4 Rxe6 2.Rf1 Kf7 3.Bb5 Qc8 4.Kg2 Kg8 5.Kg1 Kf7 
  =/+  (-0.32)   Depth: 10   00:00:05  143kN
1.Qb4 a5 2.Qb3 Rxe6 3.Rf1 Qe7 4.Qd5 Kf7 5.Qb3 Qc5+ 6.Kg2 Qc6 7.Rf4 
  =/+  (-0.36)   Depth: 11   00:00:05  157kN
1.Qb4 
  =/+  (-0.48 --)   Depth: 12   00:00:05  227kN
1.Qb4 
  =/+  (-0.60 --)   Depth: 12   00:00:05  263kN
1.Qa3 
  =  (-0.24 ++)   Depth: 12   00:00:05  497kN
1.Qa3 Rxe6 2.Rd1 Kf7 3.Qxa7+ Qe7 4.Qa4 Rd8 5.Rxd8 Qxd8 6.Be3 Kg8 7.Qb3 Qd6 8.Qd5 Qc6 
  =/+  (-0.44)   Depth: 12   00:00:05  586kN
1.Qa3 
  =/+  (-0.32 ++)   Depth: 13   00:00:05  684kN
1.Qa3 
  =  (-0.20 ++)   Depth: 13   00:00:05  698kN
1.Qa3 Rxe6 2.Rd1 Kf7 3.Qxa7+ Qe7 4.Qa4 Rd8 5.Rxd8 Qxd8 6.Kg2 Kg8 7.Be3 Rd6 8.Qb3+ Kg7 9.Kg1 Kh8 
  =/+  (-0.32)   Depth: 13   00:00:05  740kN
1.Qa3 
  =/+  (-0.44 --)   Depth: 14   00:00:05  876kN
1.Qa3 
  =/+  (-0.56 --)   Depth: 14   00:00:05  1018kN
1.Qa3 Rxe6 2.Rd1 Kf7 3.Qxa7+ Qe7 4.Qa4 Rd8 5.Rxd8 Qxd8 6.Qb3 Qa8 7.Qb4 Kg8 8.Qb3 Qc6 9.Be3 f5 10.exf5 gxf5 11.Bd4 Kg7 12.Bh5 
  =/+  (-0.44)   Depth: 14   00:00:05  1233kN
1.Qa3 Rxe6 2.Rd1 Kf7 3.Qxa7+ Qe7 4.Qa4 Rd8 5.Rxd8 Qxd8 6.Qb3 Qa8 7.Qb4 Kg8 8.Qb3 Qc6 9.Be3 f5 10.exf5 gxf5 11.Bd4 Kg7 12.Bh5 
  =/+  (-0.44)   Depth: 15   00:00:05  1307kN
1.Qa3 
  =/+  (-0.52 --)   Depth: 16   00:00:05  1556kN
1.Qa3 
  =/+  (-0.60 --)   Depth: 16   00:00:05  1752kN
1.Qd4 
  =/+  (-0.36 ++)   Depth: 16   00:00:05  2278kN
1.Qd4 
  =  (-0.18 ++)   Depth: 16   00:00:05  2394kN
1.Qd4 
  =  (0.09 ++)   Depth: 16   00:00:05  2521kN
1.Qd4 
  +/=  (0.50 ++)   Depth: 16   00:00:05  2748kN
1.Qd4 Rxe6 2.Rf1 Kf7 3.Bd1 b5 4.Bb3 Nc4 5.a4 a6 6.axb5 axb5 7.Ra1 Qc6 8.Ra7+ Re7 9.e5 Rc8 10.Rxe7+ Kxe7 11.exf6+ Qxf6 
  =  (0.04)   Depth: 16   00:00:05  3318kN
1.Qd4 
  =  (-0.08 --)   Depth: 17   00:00:05  4046kN
1.Qd4 
  =  (-0.20 --)   Depth: 17   00:00:05  4569kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 17   00:00:05  5677kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 18   00:00:05  6634kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 19   00:00:06  8052kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 20   00:00:06  11165kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 21   00:00:06  13764kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 22   00:00:07  17655kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 23   00:00:07  23761kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 24   00:00:08  32194kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 25   00:00:10  54579kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 26   00:00:12  66677kN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 27   00:00:15  101MN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 28   00:00:18  135MN
1.Qa3 Rxe6 2.Qxa7 Nf7 3.Bc4 Rxe4 4.Bb3 g5 5.Qb7 Re1+ 6.Rxe1 Qxe1+ 7.Kg2 Qe2+ 8.Kg1 Qe1+ 
  =  (0.00)   Depth: 29   00:00:23  193MN
1.Qd4 
  =  (0.08 ++)   Depth: 30   00:00:46  466MN
1.Qd4 Rxe6 2.Rf1 Kf7 3.Bd1 Qe7 4.Bb3 Nd7 5.Bd5 Rc8 6.Rf2 Kg8 7.Qa4 a5 8.Qb5 Kh8 9.Bxe6 Qxe6 10.Qd5 Qh3 11.Qf7 Qg4+ 12.Rg2 Qd1+ 13.Kf2 Qc2+ 14.Kg3 Qd3+ 15.Kf2 Qc2+ 
  =  (0.00)   Depth: 30   00:01:02  651MN
1.Qd4 
  =  (0.08 ++)   Depth: 31   00:01:35  1044MN
1.Qd4 
  =  (0.16 ++)   Depth: 31   00:01:39  1095MN
1.Qxe5 
  =  (0.28 ++)   Depth: 31   00:01:53  1255MN
1.Qxe5 
  +/=  (0.46 ++)   Depth: 31   00:01:54  1258MN
1.Qxe5 
  +/-  (0.73 ++)   Depth: 31   00:01:54  1262MN
1.Qxe5 
  +/-  (1.14 ++)   Depth: 31   00:01:54  1264MN
1.Qxe5 
  +-  (1.75 ++)   Depth: 31   00:01:55  1276MN
1.Qxe5 fxe5 2.Rf1 Qe7 3.Bd1 Rc4 4.Bb3 b5 5.Bxc4 bxc4 6.Kg2 Qe8 7.Rf2 Qe7 8.b3 cxb3 9.axb3 a6 10.Rf1 a5 11.Kg3 Qc5 12.c4 Qe7 13.Kg2 Qa3 14.h4 Qe7 15.Rf2 Qa3 16.Rf1 
  +-  (1.89)   Depth: 31   00:02:01  1346MN
1.Qxe5 
  +-  (2.02 ++)   Depth: 32   00:02:02  1357MN
1.Qxe5 
  +-  (2.14 ++)   Depth: 32   00:02:03  1363MN
1.Qxe5 
  +-  (2.32 ++)   Depth: 32   00:02:03  1368MN
1.Qxe5 
  +-  (2.59 ++)   Depth: 32   00:02:06  1403MN
1.Qxe5 
  +-  (3.00 ++)   Depth: 32   00:02:10  1451MN
1.Qxe5 fxe5 2.Rf1 Qe7 3.Bd1 Rc4 4.Bb3 b5 5.Kg2 g5 6.Bxc4 bxc4 7.b4 cxb3 8.axb3 Qg7 9.Bxg7 Kxg7 10.Rf7+ Kg6 11.Rxa7 Kf6 12.e7 Re8 13.Kf3 h5 14.b4 Rxe7 15.Ra6+ Kf7 16.Rh6 Rd7 17.Rxh5 Rd3+ 18.Kg4 Rxc3 19.Kf5 Rb3 20.Kxe5 Rxb4 21.Rxg5 
  +-  (2.66)   Depth: 32   00:02:17  1527MN
1.Qxe5 
  +-  (2.78 ++)   Depth: 33   00:02:23  1602MN
1.Qxe5 fxe5 2.Rf1 Qe7 3.Bd1 Rc4 4.Bb3 b5 5.Kg2 Qe8 6.Rf3 Qe7 7.a4 a6 8.Ba2 Qg7 9.Bxc4 bxc4 10.Bxg7 Kxg7 11.Rf7+ Kh6 12.e7 Re8 13.a5 g5 14.Rf6+ Kh5 15.Re6 g4 16.Kg3 Kg5 17.Rxe5+ Kf6 18.Rf5+ Ke6 19.Kf4 Rxe7 20.Re5+ Kd6 21.Rxe7 Kxe7 22.Kxg4 Ke6 23.Kf4 Kf6 24.Ke3 Ke5 
  +-  (2.66)   Depth: 33   00:02:27  1657MN
1.Qxe5 
  +-  (2.78 ++)   Depth: 34   00:02:30  1685MN
1.Qxe5 
  +-  (2.90 ++)   Depth: 34   00:02:31  1701MN
1.Qxe5 fxe5 2.Rf1 Qe7 3.Bd1 Rc4 4.Bb3 b5 5.Kg2 Qe8 6.Rf3 a6 7.a4 Qe7 8.Ba2 g5 9.b4 Qg7 10.Bxg7 Kxg7 11.Rf7+ Kg6 12.Bxc4 bxc4 13.b5 axb5 14.axb5 Rb8 15.Rf5 h6 16.e7 Re8 17.Rxe5 Kf6 18.Rf5+ Ke6 19.Rc5 Rxe7 20.Rxc4 Ke5 21.b6 Rb7 22.Rc6 g4 23.Rxh6 Kxe4 24.Kg3 
  +-  (2.74)   Depth: 34   00:02:41  1818MN
1.Qxe5 
  +-  (2.82 ++)   Depth: 35   00:02:43  1834MN
1.Qxe5 
  +-  (2.90 ++)   Depth: 35   00:02:44  1840MN
1.Qxe5 
  +-  (3.03 ++)   Depth: 35   00:02:50  1919MN
1.Qxe5 
  +-  (3.21 ++)   Depth: 35   00:02:51  1935MN
1.Qxe5 
  +-  (3.48 ++)   Depth: 35   00:02:56  1989MN
1.Qxe5 fxe5 2.Rf1 Qe7 3.Bd1 Rc4 4.Bb3 b5 5.a4 a6 6.Kg2 Qg7 7.Bxg7 Kxg7 8.Bxc4 bxc4 9.Rf7+ Kh6 10.Kg3 Re8 11.e7 g5 12.Rf6+ Kg7 13.Rxa6 Rxe7 14.Kg4 Rb7 15.Kxg5 Rxb2 16.Ra7+ Kg8 17.Kf6 Rf2+ 18.Kxe5 Rxh2 19.a5 h5 20.a6 Ra2 21.Kf5 Kf8 22.e5 h4 23.Ra8+ Ke7 24.a7 Rf2+ 25.Kg5 Rg2+ 26.Kxh4 
  +-  (3.51)   Depth: 35   00:03:10  2152MN
1.Qxe5 fxe5 2.Rf1 Qe7 3.Bd1 Rc4 4.Bb3 b5 5.a4 a6 6.Kg2 Qg7 7.Bxg7 Kxg7 8.Bxc4 bxc4 9.Rf7+ Kh6 10.e7 Re8 11.Kg3 g5 12.Rf6+ Kh5 13.Re6 g4 14.Rxe5+ Kg6 15.Kxg4 Kf6 16.Kf4 Rxe7 17.Rxe7 Kxe7 18.Ke5 h6 19.Kd5 Kd7 20.Kxc4 Ke6 21.b4 Kd7 22.Kd4 Kd6 23.c4 Kc6 24.c5 Kd7 25.b5 
  +-  (3.51)   Depth: 36   00:03:58  2733MN
1.Qxe5 fxe5 2.Rf1 Qe7 3.Bd1 Rc4 4.Bb3 b5 5.a4 a6 6.Kg2 Qg7 7.Bxg7 Kxg7 8.Bxc4 bxc4 9.Rf7+ Kh6 10.e7 Re8 11.Kg3 g5 12.Rf6+ Kh5 13.Re6 h6 14.h3 g4 15.h4 a5 16.Rxe5+ Kg6 17.Kxg4 Kf6 18.Kf4 Kg6 19.Rxa5 Rxe7 20.Rb5 Rf7+ 21.Ke3 Rd7 22.a5 Rd3+ 23.Kf4 Rh3 24.h5+ Kf7 25.a6 Rh4+ 26.Ke3 
  +-  (3.51)   Depth: 37   00:04:28  3110MN
1.Qxe5 
  +-  (3.59 ++)   Depth: 38   00:04:36  3205MN
1.Qxe5 fxe5 2.Rf1 Qe7 3.Bd1 Rc4 4.Bb3 b5 5.a4 a6 6.Kg2 Qg7 7.Bxg7 Kxg7 8.Bxc4 bxc4 9.Rf7+ Kh6 10.e7 Re8 11.Kg3 g5 12.Rf6+ Kg7 13.Rxa6 Rxe7 14.Kg4 Rb7 15.Kxg5 Rxb2 16.Ra7+ Kg8 17.Kf6 h5 18.h4 Rb3 19.Rg7+ Kh8 20.Rg3 Ra3 21.Kxe5 Rxa4 22.Kd4 Ra7 23.Kxc4 Rg7 
  +-  (3.51)   Depth: 38   00:04:56  3429MN
1.Qxe5 
  +-  (3.59 ++)   Depth: 39   00:04:58  3453MN
1.Qxe5 
  +-  (3.67 ++)   Depth: 39   00:05:06  3559MN

(N_A,  27.02.2016)

Two SF versions, large hash with backsliding:

Code: Select all

Analysis by Stockfish 240416 64 POPCNT (16 GB, with backsliding):

24.Qxe5 fxe5 25.Rf1 a6 26.Bd1 Rc4 27.Bb3 b5 28.a4 Qe7 29.Kg2 g5 30.Rf5 Qd8 31.Rf7 Qd2+ 32.Rf2 Qd8 33.Ba2 Qa8 34.Kg3 Qd8 35.Rf7 Qd3+ 36.Rf3 Qd6 37.Kg2 Qe7 38.Rf5 Qg7 39.Bxg7 Kxg7 40.Bxc4 bxc4 41.Kf3 Re8 42.Rxe5 h6 43.e7 Kf6 44.Rc5 Rxe7 45.Rxc4 Rf7 46.Rc6+ Ke5+ 47.Ke3 g4 48.Rc5+ Ke6 49.Rf5 Rb7 50.b4 Rc7 51.Rc5 Rf7 52.Kd4 Rd7+ 53.Rd5 Rb7 54.b5 axb5 55.axb5 Kf6 56.Rc5 Kg6 57.c4 h5 58.Rc6+ Kg5 59.Ke3 h4 60.Rc5+ Kg6 61.Kf4 g3 62.hxg3 h3 63.Rg5+ Kh6 64.Rg4 Rf7+ 65.Ke3 Rf1 66.Rh4+ Kg6 67.b6 Re1+ 68.Kf4 Rh1 69.c5 h2 70.Ke5 Kg7 71.c6 Rb1 72.c7 Rb5+ 73.Kf4 
  +-  (6.87)   Depth: 61/111   17:41:01  1224441MN, tb=313592914

(N_A,  26.04.2016)

Code: Select all

Analysis by CorChess beta 151016 x64 POPCNT (16 GB with backsliding):

24.Qxe5 fxe5 25.Rf1 Rc8 26.Bd1 b5 27.Bb3 Rc4 28.a4 a6 29.Kg2 Qe7 30.Rf2 Qe8 31.Ba2 Qa8 32.Kg3 Qe8 33.Rf1 g5 34.Rf5 Qd8 35.Rf7 Qd3+ 36.Rf3 Qd6 37.Kg2 Qe7 38.Rf5 Qg7 39.Bxg7 Kxg7 40.Bxc4 bxc4 41.Kf3 Kg6 42.e7 Re8 43.Rxe5 Kf7 44.Rf5+ Kg6 45.Ra5 Kh5 46.Rxa6 g4+ 47.Ke3 Rxe7 48.a5 Re8 49.Rc6 Ra8 50.Rc5+ Kg6 51.Kf4 h5 52.Rc6+ Kf7 53.a6 Rf8 54.Kf5 Ke7+ 55.Ke5 Kd7 56.Rh6 Rg8 57.Kf4 h4 58.Rxh4 g3 59.hxg3 Rf8+ 60.Ke3 Ra8 61.Rh6 Re8 62.Rh7+ Kc6 63.Kd4 Rd8+ 64.Kxc4 Rc8 65.Rh6+ Kc7 66.e5 Kb8+ 67.Kd5 Ka7 68.Kd6 Ra8 69.Kc5 Rc8+ 70.Kd5 Rd8+ 71.Kc4 Kb8 72.Kc5 Re8 73.Kd5 Rd8+ 74.Kc6 Rc8+ 75.Kd7 Rc7+ 76.Kd6 Rc8 77.e6 
  +- (10.71)  Depth: 68/126   15:48:16  1811931MN, tb=2147483647

(,  25.10.2016)

edit: Mike Libanan just posted a good "manual" analysis of the position after 29...cxb3 at the end of the previous page of this thread - don't miss it.

[BBauer]

First let me apologize for my illegal and sloppy notation.
Thanks for your analysis.
Following Mike Libanan's analysis I came to the following game.

[Event "GAME VARIANT"]
[Site "Chelyabinsk RUS"]
[Date "1946.??.??"]
[Round "5"]
[White "Yuri S Gusev"]
[Black "E Auerbach"]
[Result "1-0"]
[BlackElo "2400"]
[ECO "B70"]
[Opening "Sicilian"]
[Variation "Dragon, 6.Be2 Bg7 7.O-O Nc6 8.Nb3"]
[WhiteElo "2400"]
[Termination "normal"]
[PlyCount "81"]
[WhiteType "COMPUTER"]
[BlackType "cOMPUTER"]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 g6 6. Be2 Nc6 7. Nb3 Bg7
8. O-O Be6 9. f4 Rc8 10. f5 Bd7 11. g4 Ne5 12. g5 Ng8 13. Nd5 f6 14. Be3 b6
15. Nd4 Kf7 16. c3 Qe8 17. Ne6 Bxe6 18. fxe6+ Kf8 19. Nxf6 Nxf6 20. gxf6
Bxf6 21. Bh6+ Kg8 22. Rxf6 exf6 23. Qxd6 Rc6 24. Qxe5 fxe5 25. Rf1 Rc8 26.
Bd1 Rc4 27. Bb3 b5 28. Bxc4 bxc4 29. b3 cxb3 30. axb3 Qe7 31. Kg2 g5 32.
Rf2 a5 33. Rf5 Qd8 34. Rf1 a4 35. bxa4 Qa8 36. Kg3 Qd8 37. Kg2 Qd2+ 38. Rf2
Qxf2+ 39. Kxf2 g4 40. h3 g3+ 41. Kxg3 {Stalemate} 1-0

Which is not correct but anyway.
I think the queen sac is right but it is not easy to understand the complete analysis.

Kind regards
Bernhard

[MikeGL]

I think the queen sac is right but it is not easy to understand the complete analysis.

Your analysis is wrong because you allowed black Q to invade your 2nd rank
with a check. You notice on the previous page, I avoided this Q checks by
lifting the R beside the King. That's where you made mistake on your
analysis. Else this is completely winning and very easy to comprehend
because the black Q is nailed at f8 square. While your Q-side pawns would
position to seventh rank then deliver Rf8+ for the win.

regards

[tpoppins]

You two are wasting time on the 28.Bxc4 line. 28.Bxc4 is an inaccuracy that unnecessarily complicates White's task. 28.a4 is the correct move.

28.a4 a6 - what else? The c4 rook cannot move as 29.e7+ decides instantly; the b5 pawn needs support, without that support after 29.axb5 the rook is hanging
29.axb5 axb5 - forced again for the same reason
30.Ba2 - making the way for the b-pawn

and Black has no satisfactory way to meet White's simple plan: b4 and Bxc4. Note that in this line Black is denied even the shade of counterplay present in the shape of his passed a-pawn in the line you are discussing. White has a passed pawn (the b4 pawn), Black has none. White promotes the b-pawn which Black is helpless to prevent (because of the ever-present threat of Rf8#), Black takes it and White plays his e-pawn to e7 with the same inevitable mate on f8 to follow shortly.

[BBauer]

After the following moves

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 g6 6. Be2 Nc6 7. Nb3 Bg7
8. O-O Be6 9. f4 Rc8 10. f5 Bd7 11. g4 Ne5 12. g5 Ng8 13. Nd5 f6 14. Be3 b6
15. Nd4 Kf7 16. c3 Qe8 17. Ne6 Bxe6 18. fxe6+ Kf8 19. Nxf6 Nxf6 20. gxf6
Bxf6 21. Bh6+ Kg8 22. Rxf6 exf6 23. Qxd6 Rc6 24. Qxe5 fxe5 25. Rf1 Rc8 26.
Bd1 b5 27. Bb3 Rc4 28. a4 a6 29. Rf2 Qe7 30. Kg2 Qe8

I get with some back and forth play
[d]4q1kr/7p/p3P1pB/1p2p3/P1r1P3/1BP5/1P3RKP/8 w - - 4 31
using my modified SF version

Code: Select all

St-mod-17-07-07:
 1/1	00:00	 166	83k	-4,30	Rf2-f8+ Qe8xf8 Bh6xf8 Kg8xf8 Bb3xc4 b5xc4
 5/8	00:00	 8k	1.136k	+1,88	Rf2-f7 b5-b4 Rf7-g7+ Kg8-f8 e6-e7+ Qe8xe7 Rg7xe7+ Kf8xe7
 10/17	00:00	 106k	1.795k	+6,59	Rf2-f3 Qe8-e7 Bb3-a2 Qe7-g7 Ba2xc4 b5xc4 Bh6xg7 Kg8xg7 Rf3-f7+ Kg7-h6 e6-e7 Rh8-e8
 15/32	00:00	 113k	1.786k	+6,59	Rf2-f3 Qe8-e7 Bb3-a2 Qe7-g7 Ba2xc4 b5xc4 Bh6xg7 Kg8xg7 Rf3-f7+ Kg7-h6 e6-e7 Rh8-e8 Kg2-g3 Kh6-g5 h2-h4+ Kg5-h6 Kg3-g4 a6-a5 h4-h5 g6xh5+ Kg4-f5 h5-h4 Kf5-e6 Kh6-h5 Rf7-f8 Re8xe7+ Ke6xe7 h7-h6 Ke7-e6 Kh5-g4 Ke6xe5 Kg4-g3
 20/37	00:00	 140k	1.746k	+6,57	Rf2-f3 Qe8-e7 Bb3-a2 Qe7-g7 Bh6xg7 Kg8xg7 Rf3-f7+ Kg7-h6 Ba2xc4 b5xc4 e6-e7 Rh8-e8 Kg2-g3 Kh6-g5 h2-h4+ Kg5-h6 Kg3-g4 a6-a5 h4-h5 g6xh5+ Kg4-f5 h5-h4 Kf5-e6 Kh6-h5 Rf7xh7+ Kh5-g6 Rh7xh4 Kg6-g5 Rh4-h1 Kg5-f4 Rh1-h5
 25/47	00:00	 733k	2.270k	+6,59	Rf2-f3 Qe8-e7 Bb3-a2 Qe7-g7 Bh6xg7 Kg8xg7 Rf3-f7+ Kg7-h6 Ba2xc4 b5xc4 e6-e7 Rh8-e8 Kg2-g3 Kh6-h5 Rf7xh7+ Kh5-g5 Rh7-f7 Kg5-h5 h2-h4 Kh5-h6 Kg3-f3 g6-g5 h4xg5+ Kh6xg5 Rf7-f5+ Kg5-g6 Rf5xe5 Kg6-f6 Kf3-f4 a6-a5 Re5xa5 Re8xe7 Ra5-a6+ Kf6-f7 a4-a5 Re7-c7 Kf4-e5 Rc7-b7
 30/57	00:01	 4.500k	2.690k	+6,49	Rf2-f3 Qe8-e7 Bb3-a2 Qe7-g7 Bh6xg7 Kg8xg7 Rf3-f7+ Kg7-h6 Ba2xc4 b5xc4 e6-e7 Rh8-e8 Kg2-g3 g6-g5 Rf7-f6+ Kh6-g7 Rf6xa6 Kg7-f7 Kg3-g4 Kf7xe7 a4-a5 Re8-g8 Ra6-h6 Ke7-d8 Kg4-f5 g5-g4 Rh6xh7 Kd8-c8 a5-a6 Kc8-b8 Kf5xe5 Rg8-g6 Ke5-f5 Rg6xa6 e4-e5 Kb8-c8 e5-e6 Kc8-d8 Kf5-f6 Kd8-c8 Kf6-f7 Kc8-c7 e6-e7 Ra6-a8 e7-e8Q Ra8xe8 Kf7xe8+ Kc7-d6
 35/70	00:34	 97.499k	2.847k	+6,59	Rf2-f3 Qe8-e7 Bb3-a2 Qe7-g7 Ba2xc4 b5xc4 Bh6xg7 Kg8xg7 Rf3-f7+ Kg7-h6 e6-e7 Rh8-e8 Kg2-g3 g6-g5 Rf7-f6+ Kh6-g7 Rf6xa6 Re8xe7 Kg3-g4 Re7-b7 Kg4xg5 Kg7-f7 Kg5-f5 Kf7-e7 a4-a5 Rb7xb2 Ra6-h6 Rb2-a2 a5-a6 Ke7-e8 Kf5xe5 Ke8-f8 Rh6-b6 h7-h5 Ke5-e6 h5-h4 Rb6-b8+ Kf8-g7 Rb8-b7+ Kg7-g6 a6-a7 Kg6-g5 e4-e5 Kg5-f4 Ke6-d5 Ra2-a5+ Kd5-d4 Kf4-f5 Rb7-f7+ Kf5-e6 Rf7-f6+ Ke6-e7 Rf6-h6
 40/70	02:51	 478.512k	2.789k	+6,77	Rf2-f3 Qe8-e7 Bb3-a2 Qe7-g7 Bh6xg7 Kg8xg7 Ba2xc4 b5xc4 Rf3-f7+ Kg7-h6 e6-e7 Rh8-e8 Kg2-g3 g6-g5 Rf7-f6+ Kh6-g7 Rf6xa6 h7-h5 Ra6-a7 Kg7-f7 a4-a5 Kf7-e6 Ra7-c7 Re8-a8 Rc7xc4 Ke6xe7 Rc4-c5 Ke7-e6 b2-b4 Ra8-f8 b4-b5 Rf8-f1 Rc5-c6+ Ke6-d7 a5-a6 Rf1-g1+ Kg3-f2 Rg1-a1 Rc6-h6 Kd7-d8 Rh6xh5 Ra1-a5 Rh5xg5 Ra5xb5 a6-a7 Rb5-a5 Rg5-g8+ Kd8-e7 a7-a8Q Ra5xa8 Rg8xa8 Ke7-f7 Ra8-a7+ Kf7-g6 Ra7-b7

In this line White will not mate on g8 because Black returns the Queen on g7.
Now I am satisfied with this computer line.
White is winning.
Kind regards to you both.
Bernhard