December 22, 2010

Endgame tablebases

Like many other chess players, I am also following the live games of the World Women Chess Championship on the Official Website.
After Ruan Lufei has lost her second game against Hou Yifan, I started to analyse the rook endgame, which was again very interesting to check:) For the entire analysis of the game, you can visit Chess Vibes.
There are many critical moments in a game and the players have to be extremely focused all the time. Many chances suddenly appear and you have to be sharp enough to see them. But it's very difficult to calculate very deep some positions, with so many lines to be checked. The endgame tablebase (more about it at the end of today's post) doesn't have this problem, engines never get tired and thus, we can come up with the following analysis:

Ruan Lufei vs Hou Yifan

Hou Yifan played a great game, got a big advantage with Black, but after a few small inaccuracies, the following position appeared on the board:

White to play and draw!

Here Ruan Lufei played 48.Kg6? when after 48...Ra6 Black is winning.
Instead, White could have played 48.Kf6! with a draw that it is almost impossible to see, for humans. But nowdays, when endgame tablebases exists, it's easy for us to give a correct solution. If it would only be that simple for the players...
If Black goes after 48.Kf6
48...Ra6 49.Ke5 Rb6 50.Kd4 b3 51.Re1 with a draw.

Instead, on move 48 Black goes:

48...Rb5 49.Re2 and here Black has two options: taking on h5 or playing b3. Let's take a look at 49...b3 first.
49...b3 50.Rb2 Rb6 51.Ke5 Kf7 52.Kd4 Kf6 with the following position:

White to play and draw

53.Rg2! Rb5 54.Kc3 Kf5 (if 54...b2 55.Rb2 and draw) 55.Kb2 Kf4 56.Rg6 Rh5 57.Kb3 with a theoretical draw.

Let's go back to move 49 when Black could have played 49...Rh5 resulting in the position below:

White to play and draw

50.Ra2! Ke8 51.Ke6! Kd8 52.Kd6 Kc8 53.Kc6 Kb8 and now:

 54.Ra6! Rh4 55.Rb6 Ka7 (55...Kc8 56.Ra6 back and draw) 56.Rb7 Ka6 and the last and final drawing move:

57.Rb8! Rc4 58. Kd5 Rf4 59.Kc6 with a well fought draw for White!

An endgame tablebase is a computerized database that contains precalculated exhaustive analysis of a chess endgame position. The tablebase contains the game-theoretical value (win, loss, or draw) of each possible move in each possible position, and how many moves it would take to achieve that result with perfect play.
So far, all positions with 6 pieces (including kings) have been solved. Whenever you want to be sure of your analysis or to check an endgame with 6 pieces, you can go here!

Research on seven-piece tablebases is ongoing and may be completed by the end of 2015. Which makes me wonder: Chess will eventually be solved?!


  1. Dear Alina,
    Compliments for teh post today! Great endgame analysis. Teun

  2. Thank you!'s great to have an engine to help:)

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