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Luke McShane vs Fabiano Caruana
Isle of Man Grand Swiss (2019), Douglas IMN, rd 5, Oct-14
Four Knights Game: Spanish Variation (C48)  ·  1/2-1/2

ANALYSIS [x]

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Kibitzer's Corner
< Earlier Kibitzing  · PAGE 6 OF 6 ·  Later Kibitzing>
Oct-14-19  Tomlinsky: It's a draw. The b pawn is going nowhere.
Oct-14-19  fabelhaft: White b pawn falls when rook leaves third rank, so no way to progress since black b pawn and bishop always will be enough to hold
Oct-14-19  fabelhaft: For example 53. Nc1 would have won immediately but thats far from the only win McShane missed. These 2800s are tough to beat also in winning positions though.
Oct-14-19  Ulhumbrus: A look at the computer evaluations suggests that with the best play White may reach a winning position after another thirty-four moves, any single one of which may be incomprehensible to ordinary players.
Oct-14-19  devere: White King will defend the b pawn so White rook can attack the Black b pawn. Black must then have counterplay against White h pawn, which he does, or else he will lose. Black can probably hold the draw.
Oct-14-19  Ulhumbrus: My present guess is a draw although I don't rule out the possibility that White may win by means of scores of moves which are incomprehensible to an ordinary player.
Oct-14-19
Premium Chessgames Member
  diceman: Plus Luke only has 5 minutes on the clock.

Not that he will flag, it's just difficult to come up with plans.

Oct-14-19
Premium Chessgames Member
  Gypsy: This has to be a draw, doesn't it? All Black needs to do is to march forward his g-pawn and his king
Oct-14-19  devere: McShane missed a win on move 72 with Rd4 Bxh3 73.Rxb4. According to Nalimov tables with the White King on b2 it's a draw but on c2 it was a win! A difficult game, well played by both players.
Oct-14-19
Premium Chessgames Member
  Gypsy: Draw agreed. Fun game.
Oct-14-19  Tomlinsky: Good game. McShane maybe should have held off trading down but it's understandable why he went that way. Well played.
Oct-14-19
Premium Chessgames Member
  OhioChessFan: <devere: McShane missed a win on move 72 with Rd4 Bxh3 73.Rxb4. According to Nalimov tables with the White King on b2 it's a draw but on c2 it was a win!>

I had a look, and while that sounds incredible, it's rather straight forward. Anyone who wants to work on their endgame analysis should have a look. The mundane fact is the King is in the square on c2, and a move late on b2.

Oct-14-19  parmetd: Luke is going to have nightmares tonight.
Oct-14-19  spazzky: <devere: McShane missed a win on move 72 with Rd4 Bxh3 73.Rxb4. According to Nalimov tables with the White King on b2 it's a draw but on c2 it was a win!>

White rook can't go to d4 on move 72, and if you meant Re4, that draws to Bf5 pin.

Oct-14-19  devere: < spazzky: <devere: McShane missed a win on move 72 with Rd4 Bxh3 73.Rxb4. According to Nalimov tables with the White King on b2 it's a draw but on c2 it was a win!> White rook can't go to d4 on move 72, and if you meant Re4, that draws to Bf5 pin.>

You are correct. Thank you for correcting my error.

Oct-14-19
Premium Chessgames Member
  luzhin: I think the cleanest win was 53.Nc1! Qb5 (what else?) 54.Rf4 and Black can resign.
Oct-14-19
Premium Chessgames Member
  Sally Simpson: ***

The good guys, Carlsen, Caruana etc... are the good guys not because they can win games, even a slob like me can win games, it's because they are so hard to beat.

<" Luke is going to have nightmares tonight.">

Nah, he's an amatuer, a trader in London's finance, plays chess for fun.

A missing million in a bank account - that is a sleepless night.

The apparent missed wins in the ending. (I can relate to that - these wins a slob like me cannot find.)

We have to remember that there was a clock ticking in an Allegro finish on the ass end of tough 5 hour playing session.

***

Oct-14-19
Premium Chessgames Member
  OhioChessFan: I guess I should have looked at the moves leading up to the position. Still an instructive case of a King being in/out of the Queening square.
Oct-14-19
Premium Chessgames Member
  cro777: Sometimes it's harder to kill than it is to heal!

"Caruana has survived to an ending which seems to be a draw with best play" (chess24.com):

Position after 60g5


click for larger view

This position, however, is won for White. The key is to win the b4-pawn.

Instead of 61.Kg3? Luke should have played 61.Rd3! followed by 61Bf7 62.Rg3! (this was really difficult to find with "a clock ticking in an Allegro finish" as Sally remarked) with a possible continuation:

62Kh5 63.Kg1 Be6 64.Kf2 Kh4 65.Re3 Bf5 66.Re5 Bxh3 67.Re4+ g4 68.Rxb4


click for larger view

This endgame is theoretically won for White, e.g.

68Kg5 69.Rd4 Kf5 70.b4 Ke5 71.Rd1 Kf4 72.b5 g3+ 73.Kg1 Bc8 74.Rc1 etc


click for larger view

Oct-15-19  Marksen: 52.Qg4! would have won on the spot because of the threat Qh5+. 52.- Kg8 53.Re6! and most of black pieces are hanging. Unfortunately Luke played 52.Qg5? and after 52.- Qe2 Fabi managed to control the square h5.
Oct-15-19
Premium Chessgames Member
  cro777: In the aforementioned diagram after 60g5


click for larger view

Here, the immediate 61.Rg3 is also winning as demonstrated by GM Dejan Bojkov. This was the last chance for Luke to win the game.

https://www.chess.com/news/view/201...

Oct-17-19
Premium Chessgames Member
  AylerKupp: Validation of GM Bohkov's analysis (part 1 of 2)

<cro777> I just thought I'd tell you that GM Bohkov's judgment was validated by the FinalGen tablebase generator after 60...g5 61.g3 from the following position:


click for larger view

FinalGen looks at <every> legal move from each position using retrograde analysis and creates a tablebase of all replies so it's a conclusive analysis of the position. I had FinalGen analyze the position after 61.Rg3 and this is what it determined:

61...Bd5 White wins in 36 moves
61...Be6 White wins in 36 moves
61...Kh5 White wins in 36 moves
61...Bg8 White wins in 31 moves
61...Kh7 White wins in 31 moves
61...Bh5 White wins in 28 moves
61...Kg6 White wins in 20 moves
61...Kg7 White wins in 19 moves
61...g4 White wins in 19 moves
61...Bg6 White wins in 14 moves
61...Bxb3 White mates in 17 moves
61...Bc4 White wins in 17 moves

"Win" means that White achieves a decisive material advantage, in this case either by capturing Black's bishop or promoting a pawn.

So after 60...g5 Black is lost after 60.g3 in all variations. So maybe 60...g5 is Black's losing move. I decided to see if White still won regardless after 60.Re3.

In so doing I found out something very useful about FinalGen that was not obvious (at least not to me) from the existing documentation. When you start a new analysis FinalGen's work folder will either be empty (if I remembered to delete its previous tablebase from it) or it will have an existing tablebase (if I didn't remember to delete the old one). If there is an existing tablebase in its work folder FinalGen will ask you if you want to delete it or append the new tablebase to it. Normally I would be running a new analysis from a completely different position so it makes no sense to me to keep the old one, so I delete it. But this time I wanted to run an analysis from the position after 60.Re3 so I let it append the new tablebase to be generated to the existing one.

Here is where this became useful. The initial analysis of the position after 60...g5 61.Rg3 took 8 hours. But the analysis of the position after 60.Re3 took "only" 2 hours. So apparently, if you are working backwards from a previous analysis and the tablebase generated from the previous analysis is still available, it will use the information from the previous tablebase to generate the new one, saving a substantial amount of time in the process. And, since FinalGen is single-treaded, if you have a multi-core computer (who doesn't these days?) you can continue to do your regular work without reduced response time except when both FinalGen and your application are accessing the disk drive, assuming that that FinalGen and your application(s) are using the same drive.

Oct-17-19
Premium Chessgames Member
  AylerKupp: Validation of GM Bohkov's analysis (part 2 of 2)

Which should have been obvious to me but it wasn't. After all, I'm familiar with backward sliding using regular engine analysis and a large hash table which still contains most hopefully all of the previously analyzed positions so the evaluations of these positions don't have to be recalculated. So FinalGen is able to use it's previously generated tablebase and eliminate most of the calculations resulting from its retrograde analysis and significantly reduce its analysis time.

Back to the original question. After 60.Re3 White wins after any Black reply. 61...Bd5, 61...Be6, and 61...Kh5 are Black's relatively "best" responses in the sense that they delay White's win by the longest number of moves, 36. In contrast after 61...g4 White wins in 19 moves.

So, since after 59.Rxd5, 59...Bxd5 seems forced, I wanted Final Gen to analyze the position after 58.Kh2 to see if 58...Rd5 was the losing move. But unfortunately FinalGen is only able to analyze a position with one piece on either side exclusive of kings and pawns. So I though about having Stockfish 10 analyze the position after 58.Kh2 to see how it evaluated the resulting positions.

But even I don't need Stockfish for that. It's clear that any move other than 58...Rd5 probably loses the bishop, even after 58...Kg6 59.Rd4 Kf5, and Stockfish verified that for 10 possible variations. So since after 54.Rd2 the sequence 54...Qa6 (the only move that doesn't lose the queen) 55.Qh5+ Qh6 56.Qxh6+ Kxh6 57.Re1 the threat is either 58.Re2 winning the bishop or 58.Rd4 winning the Pb4, both likely leading to a simple win for White.

So maybe Black's last opportunity to save the bishop and the game was after 57.Re1. But no, Stockfish indicates that Black loses the bishop after 57.Re1 in the 10 variations that I had it examine. So Black is apparently lost after 54.Rd2. And since after 52...Qe2, 53.Nxb4 cxb4 is forced, the next candidate losing move for Black is 52...Qe2.


click for larger view

But no. Stockfish considers 52...Qe2 to be Black's best move in this position but follows it up with 53.Nc1 (instead of Caruana's 53.Nxb4) and then 53...Qg2+ 54.Qxg2 Bxg2 55.Kxg2 leaving White a rook up and an easily won game. The alternative to 53...Qg2+ is 53...Qb5 (the only move that does not lose the queen!) but then White mates in 22 starting with 54.Qh5+ Kg8 55.Rf4 Bc3 56.Qf7+ Kh8 57.Rxe4 Rxe4 58.Rd8+ Re8 59.Rxe8+ Qxe8 60.Qxe8+ Kh7 leaving White a queen up. And one ply later Stockfish uncovered a mate in 20.

So it looks like McShane missed a forced win by playing 53.Nxb4 instead of 53.Nc1. He played 53.Nxb4 after 1 min 25 secs of thought.

Oct-17-19
Premium Chessgames Member
  AylerKupp: <<Marksen> 52.Qg4! would have won on the spot because of the threat Qh5+. 52.- Kg8 53.Re6! and most of black pieces are hanging. Unfortunately Luke played 52.Qg5? >

As you see from my response to <cro777> above White wins after either 52.Qg4 or 52.Qg5 as actually played. 52.Qg4 might be a little bit quicker and that should not be discounted, but 52.Qg5 also wins assuming best play by both sides. Heck, Stockfish 10 also considers 52.Rd8 as winning convincingly, so apparently all roads lead to Rome.

Oct-17-19
Premium Chessgames Member
  cro777: <AylerKupp> Thanks for the analysis and additional information about FinalGen.


click for larger view

White to win. (Last 60g5)

In order to win White must win the b4-pawn creating a passed pawn. (He will trade his h-pawn for the b4-pawn). But first he must restrict the activity of the black king by playing Rg3.

61.Rg3 Kg6 62.h4

61.Rg3 Kh5 62.Kg1 Kh4 63.Rg4+

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