Thursday, 3 September 2009

Moving across

As you may have noticed, I haven't posted on this blog since March. It will remain up here, but I will be starting a new blog, with slightly wider range. Its focus will be chess in the entirety of the WECU area, and it can be found here.

Monday, 9 March 2009

What happened next - the answer

As you may have worked out for yourselves, the winning line for white starts 1.Kd6, after which a typical line runs 1...Kf8 2.Ke6 Kg7 3.Ke7 (gaining the opposition) Kg6 4.Kf8 Kf5 5.Kf7, and white forces the pawn home.
This is not what happened in the game.
As Simon suggested in the comments, a plausible line that only draws is 1.Kf5?! Kg7 2.g6?? Kh6!, and then 3.Kf6 is stalemate, whereas everything else drops the pawn and leads to a drawn pawn ending.
Or at least, it should do.
What actually happened was that the game did indeed continue 1.Kf5?! Kg7 2.g6?? Kh6!, and white sat there for a while thinking about how she'd thrown a winning position away.
But she sat there thinking this on black's clock time. He'd forgotten to press his clock, and his flag eventually fell, giving white the win.
What this goes to show, I'm not quite sure.

Sunday, 8 March 2009

What happened next?

This is a picture from round 1 of the Exeter Chess Congress. White to play: what happened next?

Saturday, 28 February 2009

Barnstaple v Bideford

Result of Barnstaple v Bideford match played at the Barnstaple club on Monday:

1Peter Marriott0-1Jack Rudd
2Steve Clarke1-0Peter Sandon
3Rick Dooley0-1Jon Munsey
4John Howard0-1Rob Oughton

This means Bideford, having won both matches, win the league.

Tuesday, 24 February 2009

...and over to me

About a week ago, I set you this position:

First of all, the significance: this position is from the game Pietrzycki v Rudd, from the Devon v Somerset match. The score in the other fifteen games was 7½-7½, so the match was to hang on the result of this game.

The crucial factors of this position, as I see them, are the following:

1) The black bishop is both a better piece, and a currently better-placed piece, than the white knight.

2) The black pawns are far enough advanced that they might have a decent chance of queening; the white ones are not.

3) The white rook is somewhat awkwardly placed, although it does have the good point that while it's on a4, black always has to watch for the possibility of white's playing a3.

So my take on the position is that black has a definite advantage. Is it enough for a win? My gut feeling would be probably not, but in practice it's difficult for white to defend. Among my thoughts while playing this position was that while R+B v R is a theoretical draw, it is not an easy draw, and at 40/100 + G/20, I'd fancy my chances of winning it.

In the actual game, white played 49.Ne5, to which I responded with the natural 49...Bg7. Now white missed a trick here: after 50.f4!, it is hard to see how I make progress. (50...Rxf4 51.Nd3+ Kb5, for example, can be met by 52.Rxb4+ and that's an immediate draw.) In practice, I'd have probably gone for 50...gxf3+ 51.Nxf3 Rc4, and tried to round up the a-pawn. We would have probably ended up in R+B v R at some point.

But white's actual move was 50.Ng6?!, after which white has made things rather more difficult for himself. 50...Rd2 meant white had to deal with threats to f2 and a2: the way to deal with these was probably 51.Kg3, reaching a similar position to the last line. Instead, 51.Nf4? probably pushed the position over the edge.

After 51...Kb5 52.Ra8 (52.Ra7 comes to much the same thing after 52...Be5 53.Ng6 Bd4), I then played 52...Be5 to stop the king's coming up to snaffle the g-pawn. 53.Kg3 would have been met with 53...Rd4 54.Rf8 Rxf4! 55.Rxf4 Ka4, and the black pawn easily wins the race.

(The full analysis runs 56.Kxg4 Bxf4 57.Kxf4 Ka3 58.Kg5 Kxa2 59.f4 b3 60.f5 b2 61.f6 b1=Q and now 62. f7 Qb4/b8 and 63...Qf8, or 62.Kh6 Qf5 63.Kg7 Qg5+ 64.Kf7 Kb3 and white is stuck: Ke7/f7 do not threaten to advance the pawn, and Ke6 followed by f7 allows ...Qd8.)

So white played 53.Ng6, and the game continued Bc7 54.Rc8 (what else? ...Ba5 was a serious threat whatever) Bb6 55.Ne5 Rxf2+ 56. Kg3 Rxa2 57.Kxg4. I'd managed to emerge a pawn up, and now set about shielding the b-pawn from any white pieces thinking of coming back to defend. 57...Rd2 prevented the knight's passage back to d3 (note that 58.Nc4? fails to 58...Rd4+). Thus white had to spend a tempo on 58.Kf3, after which 58...b3 59.Nc4 Rf2+ gave him an unwanted decision:

If white now plays 60.Kg3 (60.Kg4 is not all that different, except that it doesn't attack the rook.), then I play 60...Bc5, and the knight has nowhere good to go to escape the attack. Wherever it goes, I can play 61...b2. An amusing line is 60.Kg3 Bc5 61.Ne5 b2 62.Rb8+ Bb6 63.Nd7 (or 63.Nc4 Kxc4 64.Rxb6 Rd2 and my king snakes in to shepherd the pawn home) Rf6!, and the pawn queens.

So instead white tried 60.Ke4 Bc5 61.Kd5. Unfortunately for him, I'd already seen the answer to this: 61...Rf5+ 62.Ke6 Kxc4! 63.Kxf5 b2, with no way to stop the pawn queening. The game ended a few inconsequential moves later.

So in the end, I won the game and Somerset thereby won the match. (Yes, I play for Somerset, not Devon. It's because I lived in Somerset for twenty years before moving across the border.) Should I have won the game? Well, I suspect not. I get the feeling some of the contributors to the previous post would have put up a more tenacious defence than my actual opponent did.

Sunday, 15 February 2009

Over to you

This is a position from a recent game; black has just played his 48th move. The time has come, ladies and gentlemen, for you to use the Comments Box to its full potential: evaluate the position, giving analysis as appropriate.
In a later post, I shall be giving the game, its significance, and my own take on what I think of this position. But for now, it's in your hands.

Tuesday, 10 February 2009

The subtleties of pawn endings

The humble pawn endgame is one of the most fascinating parts of chess. Despite the lack of material on the board, there can be quite complex variations arising, and you need a clear head and a good understanding of the concepts concerned. Take the game Macfarlane-Munsey, played at the Barnstaple club last night:
The position on the left arose after black's 37th move. The obvious critical feature of the position is the two sides' pawn majorities, black's on the kingside and white's on the queenside. The latter is still fully mobile and white may be able to create a passed pawn from it, but the former is blocked.

Black cannot do anything to advance the pawns without losing one of them; all he can do on that side is shuffle his king. And if white plays 38.gxf5+, then after 38...Kxf5, he can't even do that. The position on the kingside is now a mutual zugzwang - black can't move without losing the e-pawn, but white can't move without allowing the black king in.

Fortunately for white, he has some free tempo moves and can play 39.b4! to force black to give way: 39...a5 is met by 40.bxa5 bxa5 41.a4, and 39...b5 is met by 40.c5, and in both cases black has run out of waiting moves and must lose the e-pawn and the game.

Instead, white let black off the hook with 38.c5??, which completely changes the character of the position. Now after 38...bxc5 39. dxc5 Ke5 40.gxf5 Kxf5, the situation has changed. White is still in the same kingside zugzwang he was in before, but black, with the pass moves Kf5-e5-d5, is not. After 41.a3 Ke5 42.b4 Kd5 43.a4, we reach the second diagram.

Here, black played the hasty 43...Kc4? to mop up the queenside pawns. Instead, 43...Ke5! was winning. Now 44.b5 cxb5 is of no use to white, because the black king can stop the c-pawn, so he's got to try 44.Ke2, but after 44...Kd4 45.Kd2 (or 45.b5 axb5 46.axb5 Kxc5 47.bxc6 Kxc6 48.Ke3 Kd5 and black has a winning endgame) 45...Kc4 46.Ke3, we've reached the position after 43...Kc4 but with black to move, rather than white. As you will see, this would have made all the difference...

...because the game continued 43...Kc4? 44.Kxe4 Kxb4 45.Kf5, reaching the third diagram, in which black made his final mistake.

After 45...Kxa4?? 46.Kxg5 Kb3 47.h4 a5 48.h5, he realized what he'd done: the white pawn would queen first and stop him from queening. He therefore resigned. And this is why the tempo in the earlier line was crucial: had black gone into this line a tempo up, he'd have been the one queening and controlling a queening square.

Had he played 45...Kxc5 instead, he'd have had a safe draw with some winning chances: 46.Kxg5 Kb4 47.h4 c5 48.h5 c4 49.h6 c3 50.h7 c2 51.h8=Q c1=Q+ will end up with a queen and a-pawn against queen ending. Black can't lose that except by walking into a skewer, and can play for a win without risk. (There may not be a win there, but that's another story.)