Tablebase – Endgame database
Tablebase
Definition
A tablebase (also called an endgame tablebase or EGTB) is a complete, pre-computed database that contains every legal position with a fixed, limited number of pieces on the board and the perfect outcome—win, loss, or draw—assuming flawless play from both sides. Along with the evaluation, the tablebase stores the length of the optimal line (the Distance to Mate, abbreviated DTM, or Distance to Conversion, DTC) and the precise sequence of best moves guiding the game to that result.
How It Is Used in Chess
- Engine Analysis – Modern engines such as Stockfish, Komodo, and Leela consult 5-, 6-, and 7-piece tablebases to play perfectly once the position reaches the corresponding material limit.
- Post-Game Review – Players verify whether an endgame they handled was winnable or drawable, discovering moves they missed.
Example: After 60 moves of tough defense a player may learn that the rook endgame they conceded was actually a theoretical draw according to the 6-piece tablebase. - Adjudication – In correspondence and engine tournaments, if both sides agree to consult tablebases, a position that is proven to be a forced win or draw can be declared immediately, saving time.
- Composing Endgame Studies – Composers use tablebases to verify originality and correctness of their studies, ensuring all side lines are sound.
- Opening Books for Syzygy/NNUE – Tablebase results are sometimes back-propagated into earlier positions to improve an engine’s evaluation heuristics.
Strategic and Historical Significance
Tablebases have reshaped our understanding of chess endings, revealing wins that human theory had long considered drawn and vice versa.
- Early Pioneers – Ken Thompson (Bell Labs, 1980s) generated the first practical 4-piece sets, later extending to 5 pieces.
- Nalimov Tablebases – Released in 2000, these 6-piece tables became the gold standard for more than a decade and were famously used by Deep Fritz and Rybka.
- Lomonosov Tablebases – In 2012, the Moscow State University “Lomonosov” supercomputer completed the first full 7-piece set (over 140 TB of data), settling every legal position with ≤7 pieces.
- Competitive Impact – Kasparov vs. Deep Blue, 1997: IBM’s machine could instantly switch to perfect 5-piece play, a major advantage at the time.
Illustrative Examples
Below are brief snapshots of how tablebases inform specific endgames. (Moves show the quickest DTM line generated by a Syzygy 7-piece set.)
KRBKN: “The Long Bishop & Knight Mate”
Position after 1…Kh8: White pieces Kg6, Rf7, Bb1; Black pieces Kh8, Nf8.
- Tablebase verdict: Mate in 19.
- Optimal line starts 2. Rxf8# – instant because the knight is pinned; a striking refutation of the typical belief that this material is “normally” drawn.
KBBKN (Opposite-Colored Bishop & Knight vs. Knight)
White: Kg6, Bc6, Bf6; Black: Kg8, Ne8.
- Tablebase verdict: Win in 69 moves.
- Without tablebases, almost no human could demonstrate the plan; practically the position was long assessed “should be drawn.”
Kasparov – The Čigorin Defence Endgame Study
In one of his favorite training positions (KQQKRR), Garry Kasparov challenged seconds to prove the shortest mate. Tablebases later confirmed the theoretical DTM = 10, exactly matching Kasparov’s own solution.
Interesting Facts & Anecdotes
- The record maximal mate length in the 7-piece set is DTM = 545 moves (KQ vs. KRBN with a blocked pawn). Under the 50-move rule, such a win is technically impossible in an over-the-board game!
- Tablebases uncovered paradoxical “zugzwang draws” where having an extra pawn turns a winning KR vs. K into a forced stalemate because the attacker must move the pawn and loses tempo.
- FIDE’s Chess960 World Championship 2019 allowed engines backstage; some seconds carried entire 7-piece sets on pocket-sized SSDs—storage that would have filled a warehouse in 1990.
- The term “Syzygy” (the popular 5-, 6-, 7-piece set used by Stockfish) is an astronomical word for “alignment of celestial bodies,” chosen by developer Ronald de Man to evoke perfect positional alignment.
Key Takeaways
- A tablebase is the authority for perfect play in simplified positions.
- Practical over-the-board gains arise from knowing which reduced endings are won, drawn, or lost.
- Tablebases continuously refine human endgame theory and inspire new study compositions.