Nollasiirto
Nollasiirto, Finnish for “null move,” is a term used in computer chess to describe a search optimization technique that speeds up alpha-beta pruning. It is applied during game-tree search by evaluating the effect of a hypothetical move in which the side to move passes its turn to the opponent, effectively making a null move. The engine then searches from that position with a reduced search depth. If the null-move evaluation exceeds the current beta bound, a cutoff is performed at the original node, allowing the engine to prune the remaining moves. The goal is to quickly detect when the opponent has a clearly strong response and to reduce the number of branches that must be explored.
In practice, nollasiirto is used with a depth-reduction parameter, often lowering the search depth by one ply
Nollasiirto has become a standard feature in modern chess engines since the 1990s, complementing other optimizations