Wednesday, May 11, 2016

Practical Rook Endgames 11: Time, Efficiency, and Alternate Realities

About three months ago, a friend sent me a game where he had this position as White with White to play:

He chose to sacrifice his bishop on this move while Black's passer was on g3 and went on to win a nailbiting race in which his f-pawn queened just before Black's h-pawn queened, White forced the exchange of the queens on h1, and then White ran to capture a6 and successfully queen his a-pawn. Later, he had afterthoughts of whether he should have waited to sacrifice. His win would have been much easier had he just played f5. If Black played g2 next, he plays Bf2, and only after g1=Q, sacrifices with Bxg1+ Kxg1 f6, when his pawn is one tempo closer to queening than the played line. If Black played Kh3, then he plays Bxg3 Kxg3 and f6 when again, his pawn is one tempo closer to queening than the played line. I thought that I would advise him that logic dictates that one should always wait until the last second to sacrifice for a queening pawn, but the last second is difficult to determine if your opponent has a way to block the sacrifice. And then study of the following ending really humbled me with regard to timing and rules of thumb.

One lovely thing about chess is that you can relive the game from the recorded score. As long as the notation isn't botched, the record of the game contains the essence of what happened. There are no dice rolls or card deck draws to reconstruct. History is captured in a half-page of alphanumeric codes. The player's thoughts and calculations can be reconstructed afterward, but the logic engines can also look at relevant lines of missed or accurately evaluated variations. The variations are like parallel universes, alternate realities, counterfactual possibilities. Guy Pearce's "Time Machine" from 2002 was itself a remake of an earlier 1960 movie adaptation of H.G. Wells' novel. One of the ideas that came up is that despite Alexander Hartdegen's ability to alter some past events, he cannot change the the mortal fate of his girlfriend.

This post is the third installment from a semifinal game from my 2015 club championship run. The game is broken into phases running roughly in reverse chronological order.

For this third installment, I'm going four moves into the past relative to the previous post. After White moved 50.Kd6, I had this position to contemplate:

I could see that I was going to have to sacrifice my rook, but that my pawns stood a chance if only I could give them enough of a head start. I needed to put my rook in a position to slow down the pawn, but still sacrifice for it when needed. My main move was Rc8. I don't specifically recall if Rh7 entered into my calculations during the game, but it's instructive to go through the exercise. So bear with me as we go into a long variation that wasn't played. Analysis variation 50...Rh7:

Black's idea is to play Rh8 and Rxc8 only when necessary. But those moments arrive earlier than expected due to some tricky variations. 51.c7 Rh8 and now 52.Rb1!!

The hard-to-see threat is that Rb8 guarantees a queen. "So what?" you say. Black can still get the pawn and try to queen his own with 52...Rc8 53.Kd7 Rxc7+ 54.Kxc7 Kf5

We've seen a position very similar to this. Recall in the previous post, that White had a choice to lock out Black's passers or try to race with his own a-pawn from this position, White to move:

In the race variation, Black barely held a draw with 54.Kb7 f3 55.Kxa7 Kf4 56.a4 f2 57.Ra1 Kg3 58.a5 Kg2 59.a6 f1=Q 60.Rxf1 Kxf1 61.Kb8 h3 62.a7 h2 63.a8=Q Kg1!=. The problem for Black is that he is now 2 tempi behind: the h-pawn is on h5 instead of h4 and when he plays f3-f2, White will not have to spend a tempo moving a rook on e1 because it moved to b1 already.

The new race would look like this:

55.Kb7 f3 56.Kxa7 Kf4 57.a4 f2 58.a5 Kg3 59.a6 Kg2 60.Kb8 f1=Q 61.Rxf1 Kxf1 62.a7 h4 63.a8=Q h3 and White just needs to use checks to get his queen to g4 and Black won't have a self-stalemate resource.

So after 50.Kd6, 50...Rc8! is the only move that draws.

At this point, I noticed that White has two logical moves: c7 or Kd7. I was really relieved when the game continued 51.c7 h4 52.Kd7 Rxc7+! 53.Kxc7 Kf5 which brings us to the drawn position at the beginning of the previous post. During the game I didn't think that I could delay the capture of the c-pawn with a move like 52.Kd7 Rh8 because of 53.Re8. I didn't notice at the time that 53...Rh7+ could keep the sacrifice bid alive and 54.Re7 Rh8 might lead to repetition. It turns out that Black has a very narrow path to draw with 55.Re8 Rh7+ 56.Kd6 Rxc7 57.Kxc7

57...f3 and White has to run his king down to f2 and trade his rook for both passers. Back to the game, I really dreaded 51.Kd7

because I thought that I had no choice but to play 51...Rxc6 52.Kxc6. Compared with the barely drawing variation above, White's king is one step closer to e2 and Black's pawn is back on h5. Two tempi mean that White has the win. If White decides to go for the a-pawn race, he sacrifices one tempo because there was no advantage to play Kc6-b7 versus Kc7-b7, but chasing Black's passer with Kd5 means that Black's h-pawn hardly gets going before the f-pawn is dead. e.g. 52...Kf5 53.Kd5 f3 54.Kd4 Kf4 55.Re8 f2 56.Rf8+ Kg3 57.Ke3 h4 58.Rg8+! followed by 59.Kxf2. In home analysis, I was astounded to see the complexity of a draw beginning with 51.Kd7 Rh8!

Didn't we just refute something like this? Three diagrams ago, Black tried to save time with the narrowly losing variation 52...Rh8 53.Re8 Rh7+ 54.Re7 Rh8 55.Re8 Rh7+ 56.Kd6 Rxc7 57.Kxc7 Kf5 58.Rf8!. But here, the pawn is still back on c6. So let's try to win the game for White beginning with 52.c7 Kf5 53.Re8 Rh7+ 53.Ke6 Rxc7 54.Kxc7. Since Black had time for 52...Kf5, he is one tempo up on the losing variation and this is just enough to draw.

One more surprising idea is that Black has a very narrow path to a draw after 51.Kd7 Rh8! 52.c7 Kf5! 53.Re8 Rh7+ 54.Re7 Rh8 55.c8=Q Rxc8 56.Kxc8. Black to move and draw:

It's hard to believe, but the only move that draws is 56...a6!! Why that pawn and why just one step? With the rook on e7 already, it's worth it for White to spend the time to capture on a7 and maneuver back to b1 or behind the leading passer. Here are some sample variations if Black doesn't find 56...a6!!

56...f3?? 57.Rxa7 Kg4 58.a4 f2 59.Rf7 Kg3 60.a5 Kg2 61.a6 f1=Q 62.Rxf1 Kxf1 63.a7 h4 64.a8=Q h3. Again, White checks with his queen until he can get to g4.

56...h4?? 57.Rxa7 h3 58.a4 f3 59.Rb7! (or 59.Rc7!) Kg4 60.a5 h2 61.Rb1! Kg3 62.a6! Kg2 63.a7! h1=Q 64.Rxh1 Kxh1 65.a8=Q Kg2. Now the technique is standard to never let the f-pawn get to f2 otherwise a drawn queen versus bishop pawn ending can arise. The white queen checks its way to g4, forcing the black king to step on f2 and then the white king moves closer to the f-pawn.

56...a5?? This is the hardest to understand, but the key is that the white rook recovers some time with threats on Black's king or pawns. 57.Ra7! Kg4 58.Rxa5 f3 59.Rb5 h4 60.a4 h3 61.a5 h2 62.Rb1 Kg3 63.a6 Kg2 64.a7 h1=Q 65.Rxh1 Kxh1 66.a8=Q is just like the previous variation.

The reason why 56...a6!! escapes with a draw is that Black's f-pawn can run pretty fast if Black's rook is out of position and a6 is just such a bad spot. 56...a6!! 57.Ra7?! f3!. White can even lose with 58.Rxa6?? f2!-+. Instead, there is still time for White to draw with 58.Rb7, Rb1 and Kb7. If White tries to improve with 56...a6!! 57.Kb7, Black still draws with the just-in-time pawn race, making sure not to be caught on g2 when the a-pawn queens.

If White had chosen 51.Kd7, I don't think I could have found the saving variations of 51...Rh8 and the impossible 56...a6!! I was just lucky my opponent didn't force the issue for me to go down in flames with 51...Rxc6?? I would say that the search for improvements in time efficiency are extremely important to look for in endgame variations, probably more so than rules of thumb about when is the best time to sac for a passer.

No comments: