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7 men tablebases

Convekta Ltd announces the release of Lomonosov Tablebases – the first complete 7-piece endgame database that includes 100%-accurate predictions and optimal solutions to every singe position possible within this limitation.

Until December 31, 2013, the tablebases will be available online and for free to all owners of ChessOK Aquarium 2012, Houdini 3 Aquarium, Houdini 3 PRO Aquarium and Chess Assistant 13, Professional Package. To access the tablebases, follow the instructions from

What are Endgame Tablebases?

Endgame tablebases are computer databases of chess endings with precise calculations for optimal play in any position, provided the number of pieces on the board does not exceed a certain limit. With Lomonosov Tablebases, this limit has gone up from 6 pieces to 7!

Simply put, the program determines if the position leads to a draw or can be won by either side – with 100% certainty. If the game can be won, the path with the least number of moves until the end of this variation is shown, given that both players make the best moves possible. If the losing player makes a suboptimal move, he will lose sooner, and the program will display the new optimal path.

The main difficulty in compiling such tablebases consists in the fact that all possible positions and variations with the desired number of pieces on the board must be thoroughly analysed and catalogued. When the piece limit is increased by one, the total number of possible situations is multiplied by about 100. This is why there is a limit to how far the precise calculations can go with the current level of computing devices.


Can a king and a knight win a position against the opponent's king assisted by 4 pieces and pawns? They can! Black Mates in 22

History Note

The first ending tablebases – for all 4-piece endgames – were built by the end of the 80-s. In the beginning of the 90-s, the same task was done for 5 pieces. In 2005, 6-piece endings were solved in Nalimov Tablebases which are now used by many professional chess programs and services.

Experts didn’t expect 7-piece endings to be cracked and catalogued until after 2015, but Convekta Ltd, namely programmers Zakharov and Makhnichev – the developers of the Aquarium interface – managed to solve this task in just 6 month using a new algorithm designed specifically for this purpose and run on the Lomonosov supercomputer based in the Moscow State University.

Lomonosov Tablebases

As a result, we now have 525 tablebases of the 4 vs. 3 type and 350 tablebases of the 5 vs. 2 type. The calculations for 6 pieces playing against a lone king weren’t done because the results are rather obvious.

The total volume of all tablebases is 140 000 gigabytes, which is obviously too much for personal computers. Lomonosov Tablebases will be accessible online from the Aquarium 2012 interface. All users of ChessOK Aquarium 2012, Houdini 3 Aquarium, Houdini 3 PRO Aquarium and Chess Assistant 13, Professional Package receive free access to the service until December 31, 2013.

To access the tablebases, follow the instructions from


During the tie-breaking match between Anand and Gelfand (May 30, 2012), the tablebases instantly detected Gelfand's decisive mistake on the 75st move.


The Interesting Part

So what new have the Lomonosov Tablebases shown us?

The most popular question would probably be about the longest mating position for 7 pieces. Well, the developers actually found the answer a couple of years ago, when they have just started working on the algorithm.











In this position, Black is to move, and he will be mated in 545 moves.

You can download the solution in .pgn and check it in your chess program. One can be sure that without the 7-piece endgame tablebases, no human player could win against a modern computer program in this position. And a chess program armed with them could probably win against any opponent for either side.


This is a position from the 9th game of the World Championship match between Steinitz and Gunsberg (New York, 1890-1891).

The game ended in a draw, but it has always been believed that Gunsberg had a winning position. In the actual game, after 73. Ra4+ he followed with 73…Kf3. But endgame textbooks claim that he could win by playing 73…Kd5.

Now, after 122 years, we finally know for a fact that there was no sure way to win that game!


The program can also search for mutual zugzwangs.

In the position to the left, if White is to move, he loses in 81; and if Black is to move, he loses in 42.


With Lomonosov Tablebases we can now look deeper into the chess endgame. As they have just been released, we will surely see more old questions answered. Though the most important is, without doubt, the contribution the tablebases can make to the further development of chess theory.

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