Fruitless Recursion as a Strategy

Luring an opponent into fruitless recursion can be an effective strategy in other games, too. One of the most colorful, bizarre, and fascinating episodes in the history of man-vs.-machine chess came in a 2008 blitz showdown between American grandmaster Hikaru Nakamura and leading computer chess program Rybka. In a game where each side got just three minutes on the clock to play all of their moves or automatically lose, the advantage surely seemed to be on the side of the computer—capable of e...

 Tablebases

t. In 1977, Thompson showed up at the World Computer Chess Championship th a new creation, a database that played the king and queen versus king and rook endgame perfectly. (KQKR is the abbreviation.) It wasn'1 an engine; there was no thinking required. Thompson had generated a database that essentially solved chess backwards, what we call retrograde analysis. It started from checkmate and worked its way back until it contained every single possible position with that material balance. Then i...

 Null Move

Called the "null move" technique, it tells the engine to "pass" for one side. That is, to evaluate a position as if one player could make two moves in a row. If the position has not improved even after moving twice, then it can be assumed that the first move is a dud and can be quickly discarded from the search tree, reducing its size and making the search more efficient. Null moves were used in some of the earliest chess programs, including the Soviet Kaissa. It's elegant and a little ironic...

 Processing Power to Chess Rating Ratio

50 here is what the Deep Thought team wrote about the relationship between search depth and chess strength in a 1989 article: The ascent of the brute-force chess machines back in the late 1970s made one thing crystal clear: there is a strong causal relationship between the search speed of a chess machine and its playing strength. In fact, it appeared from machine self-test games that every time a machine searches one extra ply, its rating increases by about 200-250 rating points. Since each...