Little Wing: a chess engine written in Rust
===========================================
[](https://github.com/vinc/littlewing/actions/workflows/rust.yml)
[](https://crates.io/crates/littlewing)
Little Wing is the successor of my previous engine [Purple Haze](https://github.com/vinc/purplehaze).
The project started in December 2014 to learn the Rust language and play with
bitboards, both experiments were conclusive and Little Wing it is still
maintained in 2026.
Currently evaluated at around 2100+ ELO on CCRL 40/4 Rating List.
[](https://asciinema.org/a/146112)
Features
--------
- Interfaces
- A nice CLI with many commands
- XBoard and UCI communication protocols
- Public API with [documented library](https://docs.rs/littlewing)
- Board representation
- FEN support
- Bitboard with LLVM CTPOP and CTTZ
- Sliding piece attacks with Hyperbola Quintessence and First Rank Attacks
- Zobrist hashing with Xorshift RNG
- Staged move generation
- MVV/LVA, SEE, and HH moves ordering by insertion sort
- Evaluation
- Tempo, Material, Mobility
- Piece Square Table (PST)
- Static Exchange Evaluation (SEE)
- Search
- Principal Variation Search (PVS)
- Quiescence Search (QS)
- Delta Pruning (DP)
- Check Extension (CE)
- Transposition Table (TT) with prefetching
- Reverse Futility Pruning (RFP)
- Null Move Pruning (NMP)
- Internal Iterative Deepening (IID)
- Futility Pruning (FP)
- Late Move Reduction (LMR)
- Killer Heuristic (KH)
- History Heuristic (HH)
Install
-------
Binaries for GNU/Linux (x86-64), Android (ARMv7), and Windows (x86-64) are
available: https://vinc.cc/binaries
If you want to compile Little Wing yourself, you must first install Rust:
$ curl https://sh.rustup.rs -sSf | sh
Then you can install the latest stable version of the engine with Cargo:
$ cargo install littlewing
Or the development version by fetching the git repository:
$ git clone https://github.com/vinc/littlewing.git
$ cd littlewing
$ export RUSTFLAGS="-C target-cpu=native"
$ export LITTLEWING_VERSION="$(git describe)"
$ cargo build --release
$ sudo cp target/release/littlewing /usr/local/bin
Usage
-----
Little Wing is compatible with XBoard and UCI communication protocols,
and in addition it has its own text-based user interface:
$ littlewing
_,;
, .--. _,-'.-;
\`-, <) o `._ ,-' ,'`_7
<_ `-\ _ _,' _.'
<_`".| `\ ` _.>
<_ ; \ _>
`" ; ``
Little Wing v0.7.0 \ | \
'|-. _ \
by Vincent Ollivier _/ / \ '.
+---+---+---+---+---+"-"`---+--'\_>
| r | n | b | q | k | b | n | r | 8
+---+---+---+---+---+---+---+---+
| p | p | p | p | p | p | p | p | 7
+---+---+---+---+---+---+---+---+
| | | | | | | | | 6
+---+---+---+---+---+---+---+---+
| | | | | | | | | 5
+---+---+---+---+---+---+---+---+
| | | | | | | | | 4
+---+---+---+---+---+---+---+---+
| | | | | | | | | 3
+---+---+---+---+---+---+---+---+
| P | P | P | P | P | P | P | P | 2
+---+---+---+---+---+---+---+---+
| R | N | B | Q | K | B | N | R | 1
+---+---+---+---+---+---+---+---+
a b c d e f g h
> move e4
+---+---+---+---+---+---+---+---+
| r | n | b | q | k | b | n | r | 8
+---+---+---+---+---+---+---+---+
| p | p | p | p | p | p | p | p | 7
+---+---+---+---+---+---+---+---+
| | | | | | | | | 6
+---+---+---+---+---+---+---+---+
| | | | | | | | | 5
+---+---+---+---+---+---+---+---+
| | | | | P | | | | 4
+---+---+---+---+---+---+---+---+
| | | | | | | | | 3
+---+---+---+---+---+---+---+---+
| P | P | P | P | | P | P | P | 2
+---+---+---+---+---+---+---+---+
| R | N | B | Q | K | B | N | R | 1
+---+---+---+---+---+---+---+---+
a b c d e f g h
> time 1 10
> show think
> play black
ply score time nodes pv
1 -46 0 1 1. ... a6
1 -45 0 3 1. ... c6
1 -22 0 4 1. ... d6
1 -20 0 5 1. ... e6
1 -1 0 14 1. ... d5
1 0 0 15 1. ... e5
1 9 0 20 1. ... Nc6
2 -47 0 53 1. ... Nc6 2. Nc3
3 9 0 278 1. ... Nc6 2. Nc3 Nf6
4 -45 0 860 1. ... Nc6 2. Nc3 Nf6 3. Nf3
4 -31 1 2437 1. ... d5 2. exd5 Qxd5 3. Nc3
5 -32 1 4647 1. ... d5 2. exd5 Qxd5 3. Nc3 Qd4
5 -20 2 7442 1. ... d6 2. Nc3 Nf6 3. Nf3 Nc6
5 0 2 11381 1. ... e5 2. Nc3 Nf6 3. Nf3 Nc6
5 1 2 12946 1. ... Nc6 2. Nc3 Nf6 3. Nf3 d5
6 -21 3 14052 1. ... Nc6 2. Nc3 Nf6 3. Nf3 d5 4. d3
7 -7 6 34813 1. ... Nc6 2. Nf3 Nf6 3. e5 Ng4 4. d4 d5
8 -29 9 53113 1. ... Nc6 2. Nf3 Nf6 3. e5 Ng4 4. d4 d6
5. h3
9 -25 27 181431 1. ... Nc6 2. d4 d5 3. e5 e6 4. Nc3 Bb4
5. Nf3 Nge7
9 -12 35 241217 1. ... e5 2. Nc3 Nf6 3. Nf3 Nc6 4. d4 exd4
5. Nxd4 d5
10 -10 50 363028 1. ... e5 2. Nc3 Nf6 3. Nf3 Nc6 4. d4 exd4
5. Nxd4 d5 6. f3
11 -7 109 815399 1. ... e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nc4 Nxe4
5. d3 Nf6 6. Nc3 Nc6
12 -23 218 1686098 1. ... e5 2. Nf3 Nf6 3. Nc3 Nc6 4. d4 exd4
5. Nxd4 d5 6. exd5 Nxd5 7. Bc4
13 -13 467 3791367 1. ... e5 2. Nf3 Nf6 3. Nc3 Nc6 4. d4 exd4
5. Nxd4 d5 6. exd5 Nxd5 7. Bc4
< move e5
+---+---+---+---+---+---+---+---+
| r | n | b | q | k | b | n | r | 8
+---+---+---+---+---+---+---+---+
| p | p | p | p | | p | p | p | 7
+---+---+---+---+---+---+---+---+
| | | | | | | | | 6
+---+---+---+---+---+---+---+---+
| | | | | p | | | | 5
+---+---+---+---+---+---+---+---+
| | | | | P | | | | 4
+---+---+---+---+---+---+---+---+
| | | | | | | | | 3
+---+---+---+---+---+---+---+---+
| P | P | P | P | | P | P | P | 2
+---+---+---+---+---+---+---+---+
| R | N | B | Q | K | B | N | R | 1
+---+---+---+---+---+---+---+---+
a b c d e f g h
> help
Commands:
quit Exit this program
help Display this screen
load [<options>] Load game from <options>
save [<options>] Save game to <options>
hint Search the best move
play [<color>] Search and play [<color>] move[s]
undo Undo the last move
move <move> Play <move> on the board
show <feature> Show <feature>
hide <feature> Hide <feature>
time <moves> <time> Set clock to <moves> in <time> (in seconds)
hash <size> Set the <size> of the memory (in MB)
core <number> Set the <number> of threads
perft [<depth>] Count the nodes at each depth
perftsuite <epd> Compare perft results to each position of <epd>
testsuite <epd> [<time>] Search each position of <epd> [for <time>]
divide <depth> Count the nodes at <depth> for each moves
uci Start UCI mode
xboard Start XBoard mode
Made with <3 in 2014-2026 by Vincent Ollivier <v@vinc.cc>
Report bugs to https://github.com/vinc/littlewing/issues
> quit
Tests
-----
Run the test suite with Cargo:
$ cargo test
Run Sequential Probability Ratio Test (SPRT) at Short Time Control (STC) with
gainer bounds:
$ make && cp target/release/littlewing littlewing-old
$ patch -p1 < something.patch
$ make && cp target/release/littlewing littlewing-new
$ sh tests/tournament.sh sprt stc gainer
Or with non-regression bounds:
$ sh tests/tournament.sh sprt stc non-regression
Little Wing also have a `perft` command for counting the number of nodes at
each depth from the starting position.
$ cargo run -- --silent
> perft
perft 1 -> 20 (0.00 s, 5.83e4 nps)
perft 2 -> 400 (0.00 s, 7.62e5 nps)
perft 3 -> 8902 (0.01 s, 7.44e5 nps)
perft 4 -> 197281 (0.16 s, 1.26e6 nps)
perft 5 -> 4865609 (3.82 s, 1.27e6 nps)
And a `perftsuite` command for comparing the results of a perft calculation
with the given EPD file.
$ cargo run -- --silent
> perftsuite tests/perftsuite.epd
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1 -> ......
r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 1 -> ......
4k3/8/8/8/8/8/8/4K2R w K - 0 1 -> ......
4k3/8/8/8/8/8/8/R3K3 w Q - 0 1 -> ......
4k2r/8/8/8/8/8/8/4K3 w k - 0 1 -> ......
r3k3/8/8/8/8/8/8/4K3 w q - 0 1 -> ......
4k3/8/8/8/8/8/8/R3K2R w KQ - 0 1 -> ......
r3k2r/8/8/8/8/8/8/4K3 w kq - 0 1 -> ......
8/8/8/8/8/8/6k1/4K2R w K - 0 1 -> ......
8/8/8/8/8/8/1k6/R3K3 w Q - 0 1 -> ......
4k2r/6K1/8/8/8/8/8/8 w k - 0 1 -> ......
r3k3/1K6/8/8/8/8/8/8 w q - 0 1 -> ......
And the usual debug commands like `divide` or `testsuite`:
$ cargo run -- --silent
> testsuite tests/wac.epd 1
2rr3k/pp3pp1/1nnqbN1p/3pN3/2pP4/2P3Q1/PPB4P/R4RK1 w - - bm Qg6 -> Qg6
8/7p/5k2/5p2/p1p2P2/Pr1pPK2/1P1R3P/8 b - - bm Rxb2 -> c3
5rk1/1ppb3p/p1pb4/6q1/3P1p1r/2P1R2P/PP1BQ1P1/5RKN w - - bm Rg3 -> Rg3
r1bq2rk/pp3pbp/2p1p1pQ/7P/3P4/2PB1N2/PP3PPR/2KR4 w - - bm Qxh7+ -> Qxh7+
5k2/6pp/p1qN4/1p1p4/3P4/2PKP2Q/PP3r2/3R4 b - - bm Qc4+ -> Qc4+
7k/p7/1R5K/6r1/6p1/6P1/8/8 w - - bm Rb7 -> Rb7
rnbqkb1r/pppp1ppp/8/4P3/6n1/7P/PPPNPPP1/R1BQKBNR b KQkq - bm Ne3 -> Ne3
r4q1k/p2bR1rp/2p2Q1N/5p2/5p2/2P5/PP3PPP/R5K1 w - - bm Rf7 -> Rf7
3q1rk1/p4pp1/2pb3p/3p4/6Pr/1PNQ4/P1PB1PP1/4RRK1 b - - bm Bh2+ -> Bh2+
2br2k1/2q3rn/p2NppQ1/2p1P3/Pp5R/4P3/1P3PPP/3R2K1 w - - bm Rxh7 -> Rxh7
r1b1kb1r/3q1ppp/pBp1pn2/8/Np3P2/5B2/PPP3PP/R2Q1RK1 w kq - bm Bxc6 -> Bxc6
Here we used `cargo run` to run the engine in debug mode, but you can invoke
it from `littlewing` if you installed it to make it run (much) faster.
The CLI as been designed to interface nicely with other Unix tools, for example
to test if the times from perft are stable you can do:
$ for i in $(seq 0 10); do littlewing -s <<< "perft 6"; sleep 1; done
Anyway, have fun with it and send me your feedback at <v@vinc.cc>!
License
-------
Little Wing is released under MIT.