Changes

Assuming the above code used a legal move generator. The algorithm is simple, short but it generates makes moves for every node even they are the leave (ends of branches). It could improve speed significantly: instead of counting nodes at "depth 0", legal move generators can take advantage of the fact that the number of moves generated at "depth 1" represents the accurate Perft value for that branch. Therefore they can skip the last [[Make Move|makemove]]/[[Unmake Move|undomove]], which gives much faster results and is a better indicator of the raw move generator speed (versus move generator + make/unmake). However, this can cause some confusion when comparing Perft valuesand may make the task of collecting some extra information such as the number of captures and checks be almost impossible.

To generate legal moves some programs have to make moves first, call a function to check if the function IsIncheck position incheck and then undo those moves. That makes the above Perft function to make and undo moves twice for all moves. Below code can avoid that problem and run much faster: