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#Online chess endgame tablebase pdf#

Checkmate: opponent’s King is in check (attacked) and unable to escape to safety.

Stalemate: opponent’s King is not in check, but your opponent has no legal moves, (remember it’s illegal to move into check).

Draw: declared when players repeat an identical board position 3 times in a row, OR when 50 moves have elapsed without a pawn move or capture taking place.

Let’s see, for example, how SpaceDog copes with the tricky KBNvsK ending: These rules and the complicated nature of some endgames make things difficult for humans to succeed in their endgame play, and chess engines struggle too, even when looking ahead many more moves.

#Online chess endgame tablebase pdf#

Here’s a snippet of SpaceDog’s attempt (before my recent additions) to play KBNvsK (the full PDF record is available here). I actually stopped the engine after 26 moves as it was clearly making no progress! If you check the full game log out, you’ll see that SpaceDog manoeuvres bravely, but is unable to work out the correct plan to trap the enemy King, even though it was looking ahead 25 moves at this point.

SpaceDog needed to trap the enemy King against the side or corner of the board to make it easier to deliver checkmate, but couldn’t coordinate its pieces correctly, and so the ending barrelled irretrievably toward a draw by the 50-move rule. It’s worth saying that SpaceDog, even armed with only its core evaluation function and search, is more than capable of winning many endgames.

But even in those cases, it can make the occasional mistake that can allow a clever opponent to salvage a draw or stalemate, or can be simply inefficient and take longer than it should to mate the opponent.