Function shakmaty::perft

pub fn perft<P: Position + Clone>(pos: &P, depth: u32) -> u64

Counts legal move paths of a given length.

Paths with mate or stalemate are not counted unless it occurs in the final position. Computing perft numbers is useful for comparing, testing and debugging move generation correctness and performance.

The method used here is simply recursively enumerating the entire tree of legal moves. While this is fine for testing there is much faster specialized software.

Warning: Computing perft numbers can take a long time, even at moderate depths. The simple recursive algorithm can also overflow the stack at high depths, but this will only come into consideration in the rare case that high depths are feasible at all.

Examples

use shakmaty::{Chess, perft};

let pos = Chess::default();
assert_eq!(perft(&pos, 1), 20);
assert_eq!(perft(&pos, 2), 400);
assert_eq!(perft(&pos, 3), 8902);