The coincidence is that two pieces with very different powers, the bishop and the knight, should nevertheless be of equal value.
Computer database analysis run by international master Larry Kaufman - now a grandmaster - showed that on average a bishop is worth 3.25 pawns, and so is a knight.
However, their values vary, depending on the position, eg a blocked position with 16 pawns would almost certainly favour the knight, while an open position with rival 3-2 pawn-majorities on the flanks would almost certainly favour the bishop.
But before a game gets down to a battle of knight versus bishop, there is another highly relevant factor to take into account: two bishops are usually worth more than two knights or a knight and bishop..
This is why annotators often highlight the win of the bishop-pair, ie when one player has two bishops and the other, for whatever reason, does not.
According to Kaufman's analysis, the bishop-pair is worth half a pawn on average.
It is often said doubled pawns are only worth 1.5 pawns. If true, this would make giving up the bishop-pair to double an opponent's pawns an even trade although, as usual, much depends on the position.
In this series I want to look at decisive games in my praxis that have got down to an ending of knight versus bishop with equal pawns.
There are none with 16 pawns on the board, so I will start with those having 14 pawns.
 |
| Black has just captured on g8 in Spanton (151) - K Griffiths (126), North London Autumn Major 1989. Who stands better, and by how much, |
*****
*****
*****
*****
*****
*****
*****
*****
*****
The pawn-structure is typical of one arising from the Exchange Variation of the Spanish. Black's four pawns on the queenside include doubled c pawns. Because of the way the white queenside pawns are set up, Black cannot make a passed pawn there by normal means. On the kingside, Black's formation is weaker than usual in that he has three isolated pawns, two of them doubled. However, White can only win if the white king can penetrate the black position, and it is not so obvious how this can be done. The analysis engine Komodo11.01 gives White a slight edge; Stockfish12 is more confident of White's chances (+1.25).
30.Kd2 c4?!
There is no need to put another pawn on a light square until obliged to do so. Generally speaking, the player with the bishop wants to keep the pawns flexible. Having said that, 30...h5!?, getting ready for mass exchanges on g4, is liked by the engines. It will be necessary at some point to develop the king, but where to? Stockfish12 suggests 30...Kg7 while Komodo11.01 narrowly prefers 30...Kf8. It is difficult for White to break through in the centre, so the former seems preferable.
31.Nc2 c5
This has the dual purpose of keeping the knight out of b4 and d4, and of preventing the white king entering the queenside via d4.
32.Ne3 Kg7 33.Ke2 f6!?
It is tempting to get rid of a doubled pawn, and this is Komodo11.01's choice, but now the knight gets access to e5, and so can invade Black's position.
34.exf6+!?
The engines prefer 33.Kf3, one point being that capturing on f6 can wait as 33...fxe5? 34.fxe5 is bad for Black.
34...Kxf6 35.Kf3 h5
Stockfish12 at first reckons White is winning while Komodo11.01 rates the position as equal. Given a little more time, they come to agree White has a slight edge.
36.Kg3 Kg6 37.Kh4 Bf7
KG offered a draw.
38.h3 Kf6?
Black had to play 38...Be6, when 39.g4? hxg4 40.hxg4 fxg4 41.Nxg4 Kf5 leaves White fighting for a draw thanks to the white king being offside. The engines give 39.g3, the point being that 39...Kh6? is a mistake because 40.g4 hxg4 41.hxg4 fxg4 42.f5! wins for White. Black should therefore drop the bishop back, eg 39...Bd7, when 40.Nd5 is only slightly better for White, according to the engines, but Black faces an unpleasant defensive task.
If White meets 38...Be6 with 39.Nf1, intending to route the knight via d2 and f3 to e5 or g5, Black has 39...Bd5, when 40.Kg3 h4+!? 41.Kxh4 Bxg2 is dead-equal, according to the engines. However White can play 40.Ne3, returning to the g3 plan.
39.g4 fxg4 40.hxg4 hxg4 41.Kxg4 Bg8
Black has no counterplay, and has to worry about his vulnerable queenside as well as the passed pawn.
42.Kf3 Ke6 43.Ke4 Bf7 44.f5+ Kd6
Worse is 44...Kf6 45.Nd5+ and 46.Nc7.
45.Kf4 Bg8 46.Ng4 Kc6 47.Ke5 b4 48.Nf6 Bf7 49.Ne4 b3 50.f6 bg6 51.Ng5 Bh5 52.f7 Bxf7 53.Nxc7 (1-0, 74 moves)
No comments:
Post a Comment