chess_ 3.3.3

This is a fast chess move generator. It has a very good set of documentation, so you should take advantage of that. It (now) generates all lookup tables with a build.rs file, which means that very little pseudo-legal move generation requires branching. There are some convenience functions that are exposed to, for example, find all the squares between two squares. This uses a copy-on-make style structure, and the Board structure is as slimmed down as possible to reduce the cost of copying the board. There are places to improve perft-test performance further, but I instead opt to be more feature-complete to make it useful in real applications. For example, I generate both a hash of the board and a pawn-hash of the board for use in evaluation lookup tables (using Zobrist hashing). There are two ways to generate moves, one is faster, the other has more features that will be useful if making a chess engine. See the documentation for more details.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62

use std::fs::File;
use std::io::Write;

use crate::bitboard::{BitBoard, EMPTY};
use crate::square::ALL_SQUARES;

// Given two squares, lookup a line between those two squares, or return EMPTY.
// This will be generated here, and then put into the magic_gen.rs as a const array.
static mut BETWEEN: [[BitBoard; 64]; 64] = [[EMPTY; 64]; 64];

// Is a number (t) between two numbers (a and b)?
fn between(a: i8, t: i8, b: i8) -> bool {
	if a < b { a < t && t < b } else { b < t && t < a }
}

// Generate the BETWEEN array.
pub fn gen_between() {
	for src in ALL_SQUARES.iter() {
		for dest in ALL_SQUARES.iter() {
			unsafe {
				BETWEEN[src.to_index()][dest.to_index()] = ALL_SQUARES
					.iter()
					.filter(|test| {
						let src_rank = src.get_rank().to_index() as i8;
						let src_file = src.get_file().to_index() as i8;
						let dest_rank = dest.get_rank().to_index() as i8;
						let dest_file = dest.get_file().to_index() as i8;
						let test_rank = test.get_rank().to_index() as i8;
						let test_file = test.get_file().to_index() as i8;

						// test diagonals first, as above
						if (src_rank - dest_rank).abs() == (src_file - dest_file).abs() && *src != *dest {
							(src_rank - test_rank).abs() == (src_file - test_file).abs()
								&& (dest_rank - test_rank).abs() == (dest_file - test_file).abs()
								&& between(src_rank, test_rank, dest_rank)
						} else if (src_rank == dest_rank || src_file == dest_file) && *src != *dest {
							(src_rank == test_rank && dest_rank == test_rank && between(src_file, test_file, dest_file))
								|| (src_file == test_file && dest_file == test_file && between(src_rank, test_rank, dest_rank))
						} else {
							false
						}
					})
					.fold(EMPTY, |b, s| b | BitBoard::from_square(*s));
			}
		}
	}
}

// Write the BETWEEN array to the specified file.
pub fn write_between(f: &mut File) {
	writeln!(f, "static BETWEEN: [[BitBoard; 64]; 64] = [[").unwrap();
	let b = unsafe { BETWEEN };
	for (i, row) in b.iter().enumerate() {
		for j in row {
			writeln!(f, "    BitBoard({}),", j.0).unwrap()
		}
		if i != 63 {
			writeln!(f, "  ], [").unwrap();
		}
	}
	writeln!(f, "]];").unwrap();
}