Singular extensions Singular extensions (SE) got their 15 minutes of fame when they were used by the Deep Blue team which won it's chess match against world champion Garry Kasparov. Since then, SE seems to have been abandoned by most. The idea of singular extensions is appealing, and what makes it so appealing is that it is game-independent: Many ideas on how to improve tree search depend heavily on the game, and therefore lack generality. Singular extensions in theory work for all games. As the name says, SE is about extensions. Up to now, I have avoided this topic, but it is important: The AlphaBeta function I have shown searches a game tree to a fixed depth. However, many lines of play are just stupid, while others are more interesting. The aim of SE is to catch some of the more interesting lines, and to search them deeper than the rest. It relies on detecting forced moves for one side, and on extending the search depth in the case of forced moves. Humans play chess like this, and can solve long variations which are forced easily. SE tries to emulate this behavior.

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