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Jan1308   InspiredByMorphy: <johnlspouge> <18...hxg6 19.Bxg6 fxg6 20.Qe5 Rxf1+ 21.Rxf1 Ne8 22.Nd5 Qxe5 23.Nxe7+ Kh7 24.Bxe5 Rb5 25.Bb2 c3> If instead black plays 25. ...cxb3 everything changes. click for larger viewNow if 26.Nxc8 bxc2 27.Bc1 Rd5 black is still in the game. Black's passed pawn probably being at least as equal in value as whites extra piece. click for larger viewAfter 25. ...cxb3 White is better off playing 26.cxb3 where one plan of action for black could be 26. ...Bb7 27.Rf7+ Kh6 28.Rf8 Rc5 click for larger viewwith threats of ...Rc2 and ...Rxg2 black appears to still be in the game. All in all it appears that 18. ...hxg6 was the correct reply for black. 

Jan1308   InspiredByMorphy: <johnspoulge> Perhaps in the line above white is better off playing 26.axb3
where one continuation may be ...Rc5 26.c4 e5 where keeping blacks rook out of the action may help maintain whites positional + 1 pawn advantage. click for larger view 

Jan1308
  johnlspouge: <InspiredByMorphy: <johnspouge>> Thanks for your analysis.
I included the computer line to the end according to the principle of not destroying information when communicating (scientific) results. Of course, near the end of its plies, the computer line is going to miss much that a human can see. In an exceptionally complicated situation like today's, it would be desirable to run computer analysis for hours rather than minutes, to check that the evaluation is stable as the plies increase. I recommend that a few other people download freeware, so we can devote a few more computer cycles to the analyses ;>) 

Jan1308
  johnlspouge: <InspiredByMorphy: All in all it appears that 18. ...hxg6 was the correct reply for black.> I ran Toga II 1.3.1 for an extra ply
[ply 16, time 13:40, value +3.10]
18...hxg6 19.Bxg6 fxg6 20.Qe5 <Ne8> 21.Nd5 Qxe5 22.Nxe7+ Kh7 23.Bxe5 Rxf1+ 24.Rxf1 Rb5 25.Bb2 cxb3 26.axb3 Rc5 27.Rf8 e5 28.Rxe8 Rxc2 29.Nxc8 Rxb2 30.h4 Rxb3 31.Re7+ Kh6 32.Rxe5 Interestingly, the highlighted 20...Ne8 diverged from earlier analysis (and was present at ply 15, time 0:35, value +2.98, as well). I have not discovered any detailed description of the Toga algorithm, but the program appears to learn, because it found its 15ply line much faster than before. I will let the program run some more, and let you know if there is a drastic change in the evaluation. Personally (having done a little human analysis on the position as well ;>), the variation played out to 21.Qg4 was probably best play. It is hard for me to believe that Black is better off with 18...hxg6 than 18...cxd3. With 18...hxg6, he lets the Bd3 sacrifice itself for a valuable defensive Kside P, and without 18...cxd3, the Pc4 never becomes a dangerous passer. 

Jan1308
  johnlspouge: <InspiredByMorphy>, Toga II 1.3.1 [ply 18, time 1:27:36, value +3.32] gave the same moves as ply 15 out to 26...Rc5. I know by experience that each ply doubles to triples the previous calculation time, and I would like my computer back ;>) 

Jan1308   MaczynskiPratten: I think over the board 18..cxd3 is better than 18...hxg6 because it is easy for White to follow up after the latter, but with the former he has to find the very difficult 21 Qg4! to keep the attack going effectively. 

Jan1308   Cinco: <johnlspouge>, Fritz likes two lines here. 18.f5xg6 c4xd3 19.g6xh7+ Kg8h8 20.Nc3d5+ f7f6 21.Qe2g4 e6e5 22.Qg4g8+ Rf8xg8 23.h7xg8Q+ Kh8xg8
± (1.22) Depth: 18/42 230mN
And
18.f5xg6 c4xd3 19.Qe2h5 h7xg6 20.Qh5h6 Be7g5 21.Qh6xg5 Nd6c4 22.Nc3d5 e6xd5 23.Bb2d4 Nc4e3 24.Qg5xe3 f7f6 25.Rf1xf6 Rf8xf6 26.Bd4xf6 Bc8f5
(1.97) Depth: 18/42 23796kN
Thoughts on this second line with 19. Qh5? 

Jan1308
  johnlspouge: Hi, <Cinco>. Welcome to chessgames.com! Since you have your own oracle, I assume you are asking me for a human evaluation :) My analysis did not consider 19.Qh5 as a candidate against 18...cxd3, but this was an oversight on my part. The counter 20...f6 is what necessitated the second key move 21.Qg5 in the game. Over the board, therefore, if you do not have Van der Wiel's calculating abilities (or his intuition, maybe), 19.Qh5 would be a powerful alternative to 19.gxh7+, as it permanently excludes ...f6 (because of Qxg6+), thereby simplifying the lines enormously. As I calculated, I was impressed that certain thematic moves kept recurring in different variations. In practice, I would have excluded ...f6 gladly, even if it cost a few centiPs :) As far as I know, Toga does not offer alternatives to its best lines, so thank you for taking the hint and providing your own computer analysis. 

Jan1308   InspiredByMorphy: <johnlspouge>You are correct in your analysis in concluding that 18. ...hxg6 doesn't really do the trick for black. 

Jan1408   D.Observer: Would <18. ♗d4> work? 

Jan1408
  johnlspouge: <D.Observer>: I assume you mean 18.Be4. It loses (or at least creates disadvantage), as I pointed out. Toga II 1.3.1 [ply 15/48, time 05:59, value 0.65]
18.Be4 Nxe4 19.Nxe4 exf5 20.Nf6+ Bxf6 21.Bxf6 Rb6 22.Bd4 Re6 23.Qxc4 Qxc4 24.bxc4 Re4 25.c3 Rfe8 26.c5 Bb7 27.Kg1 Bd5 28.Rf2 f4 29.Bf6 Bc4 30.g3 Re1+ 31.Rxe1 Rxe1+ 32.Kg2 Bd5+ 33.Kh3 fxg3 34.hxg3 

Jan1408
  kevin86: White gives up a piece so that the pawn can gobble up black's king protection. A strange series of forksat one time white's rooks are forked by a bishop,then he moves one to a square attended by the SAME bishop. 

Jan1408
  patzer2: For the Sunday Jan 13, 2008 puzzle solution, White sacrifices his Bishop in order to attack the weakened Black castled position with 18. fxg6!! The discovered check followup 20. Nd5+! plays a major role in securing White's victory, by enabling him to snare the Queen toward the end of the combination with a clear and probably decisive material advantage. 

May1520   Brenin: I saw that 18 fxg6 cxd3 19 gxh7+ Kh8 20 Nd5+ f6 21 Qg4 looks promising, but I couldn't work out all the possible Black responses. 

May1520
  chrisowen: Damsbite keenmank keyimank keysmank dinkmank pg6jaffa gonemank keenmank keyimank pd3jaffa donemank keenmank keyimank junks it a giveguff 18hxg6 kestrels keyamank mankadds bonegood keenmank
keyimank gonemank keenmank keyimank 1 it ok keyomank ph7jaffa honemank keenmank keyimank kh8jaffa honemank keenmank keyimank nd5jaffa donemank keenmank keyimank pf6jaffa faffmank junks it a 21.Qg4 kestrels keyamank honedits tellmank keenmank keysmank gonemank keenmank keyimank keystink 2 3 it ok keyomank damsbite keenmank keyimank widowadd faffmank jaffaman keysmank umsumums donegood clogmank bonegood keenmank keyimank dinkmank rebindja
buffmank miglight iamsanna keyamank damsbite keyomank pg6jaffa gonemank 

May1520   Brenin: After 18 fxg6 cxd3 19 gxh7+ Kh8 20 Nd5+ f6 21 Qg4, Black's best defence seems to be 21 ... e5 22 Qg8+ Rxg8 23 hxg8=Q+ Kxg8 24 Nxc7, leaving White the exchange up with a better position. If 21 ... exd5 or Qxc2 then 22 Rxf6 leads to mate in a few moves. 

May1520   Andrew Chapman: <If 21 ... exd5 or Qxc2 then 22 Rxf6 leads to mate in a few moves.>When considering exd5, one has to see that after 22..BxQ white has Rf7, rather than only seeing that the attractive Rxf8 loses. 

May1520
  agb2002: Black threatens cxd3.
The weakened black castle suggests 18.fxg6:
A) 18... cxd3 19.gxh7+
A.1) 19... Kh8 20.Nd5+ f6 (20... Kxh7 21.Qh5+ Kg8 22.Qh8#) 21.Qg4 A.1.a) 21... exd5 22.Rxf6
A.1.a.i) 22... Bxg4 23.Rf7+ and mate in two.
A.1.a.ii) 22... Bxf6 23.Bxf6+ Kxh7 (23... Rxf6 24.Qg8#) 24.Qh5+ Kg8 25.Qg6+ Qg7 26.Qxg7#. A.1.b) 21... e5 22.Qg8+ Rxg8 23.hxg8=Q+ Kxg8 24.Nxc7 seems to win an exchange at least. A.1.c) 21... Qxc2 22.Nxe7 Qxb2 23.Qg8+ Rxg8 24.hxg8=Q#. A.2) 19... Kxh7 20.Qh5+ Kg8 21.Qg4+ Kh7 22.Rf3 Nf5 23.Rh3+ Nh6 24.Bc1 wins. A.3) 19... Kg7 20.Qg4+ is similar to previous lines. B) 18... hxg6 19.Qe5
B.1) 19... cxd3 20.Nd5 f6 (20... exd5 21.Qg7#) 21.Nxf6+ (21.Qg3 exd5 22.Qxg6+ Kh8 23.Rf4 Nf5 24.Rf3 Ng7, unclear) B.1.a) 21... Bxf6 22.Rxf6 and Black's king and queen have serious problems to protect g6, f8, d6, etc. For example, 22... Rxf6 23.Qxf6 Rb7 24.Qxg6+ Kf8 25.Rf1+ Ke7 (25... Nf5 26.Ba3+ wins decisive material) 26.Qg7+ Kd8 27.Rf8+ Ne8 28.Bf6+ wins decisive material. B.1.b) 21... Rxf6 22.Rxf6 looks similar or transposes to B. 1.a. For example, 22... Bf8 23.Rxg6+ Kf7 24.Rg7+ Bxg7 25.Qxg7+ Ke8 26.Qxc7 wins. B.2) 19... f6 20.Qg3
B.2.a) 20... cxd3 21.Qxg6+ Kh8 22.Rf3 e5 23.Qh5+ Kg7(8) 24.Rg3+ Bg4 25.Rxg4#. B.2.b) 20... g5 21.Bxc4 wins a pawn at least (21... Nxc4 22.Qxc7). C) 18... fxg6 19.Qe5
C.1) 19... Bf6 20.Rxf6 Rxf6 21.Qxf6 cxd3 22.Nd5
C.1.a) 22... exd5 23.Qh8+ Kf7 24.Qg7+ Ke8 25.Qxc7 wins. C.1.b) 22... Qh7 23.Ne7+ wins.
C.2) 19... Rxf1+ 20.Rxf1, with the double threat Qg7# and Qh8#, wins. D) 18... f5 19.gxh7+ Kxh7 (19... Kf7 20.Qh5+ and 21.Nd5+ wins) 20.Qh5+ Kg8 21.Qg6+ Kh8 22.Nd5+ wins. 

May1520
  FSR: Beautifully played by van der Wiel. 

May1520
  chrisowen: A walk in the woods no? 

May1520
  Breunor: I had good instincts but unfortunately can't calculate this kind of puzzle; I looked at the first three moves right away but I didn't see Qg4; even if I had this was way beyond my skill level. 

May1520   RandomVisitor: After 16.Bb2 black is doing fine, perhaps now 16...Bf6 leads to an even game click for larger viewStockfish_20051519_x64_modern:
<53/22 11:39 0.00 16...Bf6 17.Na4 Bxb2 18.Nxb2 Bb7> 19.Qe5 Rfd8 20.Rad1 a5 21.Rf2 a4 22.Kg1 axb3 23.axb3 Qb6 24.Na4 Qb4 25.Nxc5 Ra5 26.Qf6 Raa8 

May1520   RandomVisitor: After 17...c4 there is 18.fxg6 cxd3 19.<Qh5> hxg6 20.Qh6 and a position so powerful that black must return the piece with 20...Bg5 click for larger viewStockfish_20051519_x64_modern:
<54/93 50:09 +4.94 18.fxg6 cxd3 19.Qh5 hxg6 20.Qh6 Bg5> 21.Qxg5 Ne8 22.Rae1 Bb7 23.Ne4 Bxe4 24.Rxe4 Qxc2 25.Qe5 f6 26.Qxb8 d2 27.Rd4 Qxb2 28.Rd8 Qc1 29.Qf4 d1Q 30.Rdxd1 Qxf4 31.Rxf4 Rf7 32.Rd8 Kf8 33.Rc4 Re7 34.Rc6 g5 35.a4 a5 36.Ra8 Rd7 37.Kg1 Rd1+ 

May1520   Olavi: Analyzing in 1989 Van der Wiel concluded that 19.Qh5 wins as well, but he seems to be happy with 19.gxh7+ since it's more beautiful. 

May1620   RandomVisitor: Curious is the position after 5...d6 where the machine after several hours of thinking likes 6.g4 click for larger viewStockfish_20051519_x64_modern:
<59/93 10:23:57 +0.67 6.g4 h6 7.Be3 a6 8.h4> b5 9.Bg2 b4 10.Na4 Bd7 11.g5 hxg5 12.hxg5 Rxh1+ 13.Bxh1 Bxa4 14.gxf6 Nc6 15.b3 Bb5 16.a4 bxa3 17.c4 Nxd4 18.Qxd4 e5 19.Qd5 Bd7 20.fxg7 Bxg7 21.Bf3 Be6 22.Qc6+ Ke7 23.Qb7+ Bd7 24.Rxa3 Qc8 25.Qxc8 Bxc8 



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