Touch-move rule the player touches his rook at the same time as touching the king, he must castle with that rook if it is legal to do so. If the player completes a two-square king move without touching a rook, the player must move the correct rook accordingly if castling on that side is legal. Otherwise, the move must be withdrawn and another king move made. When a pawn is moved to its eighth , once the player takes his hand off the pawn, a different move of the pawn can no longer be substituted. However, the move is not complete until
Null-move heuristic null-move heuristic in zugzwang positions, most chess-playing programs that use the null-move heuristic put restrictions on its use. Such restrictions often include not using the null-move heuristic if Another heuristic for dealing with the zugzwang problem is Omid David and Nathan Netanyahu's verified null-move pruning. In verified null-move pruning, whenever the shallow null-move search indicates a fail-high, instead of cutting off the search from the current node, the search is continued with reduced depth. Null-move heuristic In computer chess programs, the null-move heuristic is a heuristic technique used to enhance the speed of the alpha-beta pruning algorithm. Alpha-beta pruning speeds