# chessgen
[](https://github.com/dsaiko/chessgen/actions)
[](https://github.com/dsaiko/chessgen)
[](https://crates.io/crates/chessgen)
[](https://docs.rs/chessgen)
A simple and fast chess moves generator.
This is my next and probably last rewrite of a chess moves generator into a new programming language.
Since 2014, I have implemented the same engine in:
- C
- [C++](https://github.com/dsaiko/sachista-chess)
- Java
- Scala
- [Swift](https://github.com/dsaiko/sachista-chess-swift)
- [Go](https://github.com/dsaiko/sachista-chess-go)
- [Rust](https://github.com/dsaiko/chessgen)
Rust implementation is the newest and most advanced in terms of code quality and features.
## Performance comparison between different language versions.
[PerfT](https://www.chessprogramming.org/Perft) computes number of all possible moves for a given depth and is a common
way how to test performance and result of a chess generator.
Rust implementation is very comparable in performance to C++ and it surprisingly behaves faster for bigger depth of
moves.
The reason for a longer startup of a perft binary is probably an initialisation of a cache array using a loop and Mutex:
```
cache: Box<[Mutex<PerfTCacheEntry>]>
...
let mut cache = Vec::with_capacity(cache_size);
for _ in 0..cache_size {
cache.push(Mutex::new(PerfTCacheEntry::new()))
}
```
vs C++
```c++
std::atomic<CacheEntry> *cache;
...
cache = new std::atomic<CacheEntry>[cacheSize];
```
Bellow are perft results for a standard chessboard layout on my AMD Ryzen 7 5800H, Ubuntu 23.04.
<pre>
PERFT 7: 3,195,901,860 combinations
PERFT 8: 84,998,978,956 combinations
PERFT 9: 2,439,530,234,167 combinations
</pre>
Multithreaded, with cache:
<pre>
_______| PERFT 7 _| PERFT 8 __| PERFT 9 __|
C++: | 1.05s | 28.99s | 36m45s |
Rust: | 1.59s | 26.28s | 20m13s |
GO: | 2.88s | 2m16s | --- |
</pre>
Multithreaded, no cache:
<pre>
_______| PERFT 7 _| PERFT 8 __| PERFT 9 __|
C++: | 3,850 | 1m52s | 54m17s |
Rust: | 3.78s | 1m56s | 58m48s |
GO: | 18.38s | 9m57s | --- |
</pre>
## Examples
### Initializing ChessBoard
```rust
use chessgen::ChessBoard;
fn main() -> Result<(), Box<dyn std::error::Error>> {
// standard chess board
let mut board = ChessBoard::STANDARD;
// creating board from FEN
board = ChessBoard::from_fen(ChessBoard::STANDARD_BOARD_FEN)?;
board = ChessBoard::from_fen("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1")?;
// creating board from String representation
board = ChessBoard::from_string(
"
a b c d e f g h
8 r n b q k b n r 8
7 p p p p p p p p 7
6 - - - - - - - - 6
5 - - - - - - - - 5
4 - - - - - - - - 4
3 - - - - - - - - 3
2 P P P P P P P P 2
1 R N B Q K B N R 1
a b c d e f g h
",
)?;
// creating board from String representation without decoration
board = ChessBoard::from_string(
"
r n b q k b n r
p p p p p p p p
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
P P P P P P P P
R N B Q K B N R
",
)?;
println!("{}", board);
Ok(())
}
```
Output:
<pre>
a b c d e f g h
8 r n b q k b n r 8
7 p p p p p p p p 7
6 - - - - - - - - 6
5 - - - - - - - - 5
4 - - - - - - - - 4
3 - - - - - - - - 3
2 P P P P P P P P 2
1 R N B Q K B N R 1
a b c d e f g h
</pre>
### Generating attacks and moves
See: [ChessProgramming Pseudo Legal Move](https://www.chessprogramming.org/Pseudo-Legal_Move)
```rust
use chessgen::{ChessBoard, Color};
fn main() -> Result<(), Box<dyn std::error::Error>> {
let board = ChessBoard::from_string(
"
- - - - q - - k
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - B - - -
- - - Q K - - -
",
)?;
// attacks
println!("Attacks:\n{}", board.attacks(Color::Black));
// legal moves
print!("Legal moves: ");
for m in board.legal_moves() {
print!("{} ", m)
}
println!("\n");
// pseudo legal moves
print!("Pseudo legal moves: ");
board.moves(&mut |m| print!("{} ", m));
println!("\n");
Ok(())
}
```
Output:
<pre>
Attacks:
a b c d e f g h
8 x x x x - x x x 8
7 - - - x x x x x 7
6 - - x - x - x - 6
5 - x - - x - - x 5
4 x - - - x - - - 4
3 - - - - x - - - 3
2 - - - - x - - - 2
1 - - - - - - - - 1
a b c d e f g h
Legal moves: d1a1 d1b1 d1c1 d1d2 d1d3 d1d4 d1d5 d1d6 d1d7 d1d8
d1c2 d1b3 d1a4 e1f1 e1d2 e1f2
Pseudo legal moves: d1a1 d1b1 d1c1 d1d2 d1d3 d1d4 d1d5 d1d6
d1d7 d1d8 e2f1 e2d3 e2f3 e2c4 e2g4 e2b5 e2h5 e2a6 d1c2 d1b3
d1a4 e1f1 e1d2 e1f2
</pre>
### Applying a move
```rust
use chessgen::{ChessBoard, Move};
fn main() -> Result<(), Box<dyn std::error::Error>> {
let mut board = ChessBoard::from_string(
"
- - - - q - - k
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - B - - -
- - - Q K - - -
",
)?;
board = board.validate_and_apply_move(&Move::from_string("d1d8")?)?;
println!("{}", board);
Ok(())
}
```
Output:
<pre>
a b c d e f g h
8 - - - Q q - - k 8
7 - - - - - - - - 7
6 - - - - - - - - 6
5 - - - - - - - - 5
4 - - - - - - - - 4
3 - - - - - - - - 3
2 - - - - B - - - 2
1 - - - - K - - - 1
a b c d e f g h
</pre>
### Running PerfT
```rust
use chessgen::{ChessBoard, PerfT};
use std::time::Instant;
const CACHE_SIZE: usize = 64 * 1024 * 1024;
/// Run PerfT at specific board and depth.
fn main() -> Result<(), Box<dyn std::error::Error>> {
let board = ChessBoard::STANDARD;
let depth = 5;
let start = Instant::now();
let count = PerfT::new(CACHE_SIZE).perft_n(&board, depth);
let duration = start.elapsed();
println!("perfT finished:");
println!(" FEN: {}", board.to_fen());
println!(" depth: {}", depth);
println!(" count: {}", count);
println!(" time: {:?}", duration);
Ok(())
}
```
Output:
<pre>
perfT finished:
FEN: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
depth: 5
count: 4865609
time: 1.363183325s
</pre>
### Displaying chess board
You may implement custom display of the chessboard using
```
ChessBoard::piece_at()
```
```rust
use chessgen::{ChessBoard, Index};
/// Run PerfT at specific board and depth.
fn main() -> Result<(), Box<dyn std::error::Error>> {
let board = ChessBoard::STANDARD;
for i in Index::ALL_FIELDS {
if i.index > 0 && i.rank() != Index::new(i.index - 1).rank() {
println!();
}
let file = i.file();
let rank = i.rank();
// translate ranks for a display as rank 0 is the most bottom rank
let translated_i = Index::from_rank_and_file(7 - rank, file);
let output = match board.piece_at(translated_i) {
Some((color, piece)) => piece.to_char(color),
None => '-',
};
print!(" {} ", output);
}
println!();
Ok(())
}
```
Output:
<pre>
r n b q k b n r
p p p p p p p p
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
P P P P P P P P
R N B Q K B N R
</pre>