Null move

Article summary

In game theory, a null move or pass is a decision by a player to not make a move when it is that player's turn to move. Even though null moves are against the rules of many games, they are often useful to consider when analyzing these games. Examples of this include the analysis of zugzwang (a situation in chess or other games in which a null move, if it were allowed, would be better than any other move), and the null-move heuristic in game tree analysis (a method of pruning game trees involving making a null move and then searching to a lower depth). The reason a reduced-depth null move is effective in game tree alpha-beta search reduction is that tactical threats tend to show up very quickly, in just one or two moves. If the opponent has no tactical threats revealed by null move search, the position may be good enough to exceed the best result obtainable in another branch of the tree (i.e. "beta"), so that no further search need be done from the current node, and the result from the null move can be returned as the search value. Even if the null move search value doesn't exceed beta, the returned value may set a higher floor on the valuation of the position than the present alpha, so more cutoffs will occur at descendant sibling nodes from the position.…

Key claims

No claims recorded.

Discussion questions

1. Summarise the article in your own words. Which single claim would you verify first, and why?
2. Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
3. If two sources disagreed about one of these facts, what would you need in order to trust one over the other?

Bibliography

No sources recorded.