31 January 2018

Keep Forking

Last week and this, I've been using my time on the bus to solve a few tactics exercises on Chess.com. I have attempted more than one hundred, finding that my concentration on the bus is often less than optimal, especially on the small screen of my phone. This afternoon, I muffed several easy ones by moving too quickly and skipping an elementary step in calculation, then spent three and a half minutes on this one.

White to move

I found the solution, then got several more correct.

28 January 2018

Study Material

Chess Informant 134 contains an article by Ivan Ivanisevic on "The Art of Unequal Exchange" that has material suitable for chess players across a range of skill levels. An unplayed variaton in his first game fragment offers some positions highlighting fork threats.

Black to move

The game is Gurieli,N. -- Matveeva,S., Moscow 1986. In the game, White played 15.Kxh2 and Black won back the sacrificed queen. Ivanisevic suggests 15.Re1 Rxg2+ 16.Kf1, which leads to the position in the diagram above.

White's battery on the e-file appears menacing. But after 16...e5 17.Qxe5, Black draws with a perpetual that forces repetition. Alternatives give Black White's queen for a rook via a knight fork. Black's material advantage should prove decisive.

Ivanisevic begins his article with this position.

Black to move

Black played 10...Qxd4! Simple tactics allowed White to win the Black queen, but in the resulting position, White's queen and king proved vulnerable. To this game fragment, the author adds material from historic games and several played more recently.

There is a 1962 game where Rashid Nezhmetdinov's three minor pieces were superior to a queen and rook due to the enemy king's vulnerability. There is a 1994 blitz game between Garry Kasparov and Vladimir Kramnik. Among the other games are a nice queen sacrifice by Hou Yifan and another by Fabiano Caruana.

Ivanisevic also includes one of his own games, a game where engines have shown in the decades since the game was played that his opponent missed several chances for clear advantage. Such positions offer good training material for sitting at a board and struggling through the imbalances and plans without silicon assistance.

White to move

From Drasko,M. -- Ivanisevic,I, Pale 1997.

23 January 2018

On the Bus

During the bus ride from the college town where I am teaching a class this quarter back into the city where I park my car, I attempted fifteen tactics exercises yesterday. This is one of those that I failed.

Black to move (diagram upside down with Black on bottom)

It is exercise 660988 on Chess.com.

22 January 2018

Checkmate Data

It is commonplace to speak and write about checkmate patterns. Certain recurring checkmates happen over and over again in games no matter the skill level of the players. Of course, once players rise above a certain level, checkmates become rare due to resignation either due to a checkmate threat or one player gaining an overwhelming material advantage.

Do claims about checkmate patterns stand up to data from played games? It is a simple, albeit time consuming matter to examine every game in the database that ended in checkmate. It may be possible to name every pattern in these checkmates and then list them in order of frequency.

Running on my desktop, ChessBase was able to find every game in my largest database ending in checkmate in about one minute. As I prefer quality over quantity, my largest database is smaller than many others, containing a mere 5.9 million games.

In this database, 148,127 games end in checkmate.

The last piece to move was most often the queen, and presumably this piece was always giving the check that is checkmate in all of them. Queen moves account for 59% (87,894) of the games in this selection.

The rook is the last piece to move in 24% (35,473) of the games. Most often, the rook is likely giving check and mate. However, a rook move can produce a discovered check by bishop or queen.

A little more than 7% (10,990) of the games ending in checkmate involve a knight making the last move of the game. Some of these, no doubt will be discoveries, but it's a reasonable prediction that the knight is checking the enemy king in most of them.

A bishop moves to checkmate the opponent in 6% (8,898) of the games.

Pawn moves account for slightly more than 3% (4,847) of the games. It will be interesting to study how often the pawn itself delivers the decisive check.

King moves account for a mere 25 games. More than half of these are by castling, so a rook is giving checkmate. The king cannot deliver check, but it can cut off the escape of an enemy king.

For example, in this game between two youth players from 2005, White's king moved so as to check by the rook and cover one of the escape squares.

White to move

One of the games that ended with O-O# could have gone on two moves longer with better defense. The combination strikes me as instructive. It is from Suess -- Hurme 1969, a game played as part of team world championship qualifier.

White to move

13 January 2018

Beware the Horse

Where should the queen move?

White to move

This position caught my interest. It appears in "The Art of Unequal Exchange" by Ivan Ivanisevic in Chess Informant 134, which I received last week. This article is quite interesting and offers study material that promises to improve my game, as well as helping me develop some materials for teaching young players.