Little Wing

A bitboard chess engine written in Rust.

A work in progress since December 2014.

Board representation
- Bitboard with LLVM CTPOP and CTTZ
- FEN support
- Zobrist hashing
- Staged moves generation
- MVV/LVA and SEE moves ordering with insertion sort
Search
- Principal variation search
- Quiescence search
- Transpositions table
- Null move pruning
- Internal iterative deepening
- Futility pruning
- Late move reduction
- Killer heuristic
Evaluation
- Piece square table evaluation
- Mobility evaluation
- Static exchange evaluation
Interface
- CLI with play and debug commands
- XBoard and UCI communication protocol
- Public API with documented library

Tested on GNU/Linux 32 and 64 bits, should run anywhere.

Usage

First you need to 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
$ LITTLEWING_VERSION=$(git describe) cargo build --release
$ sudo cp target/release/littlewing /usr/local/bin

Little Wing is compatible with XBoard and UCI communication protocols, in addition it has its own text-based user interface:

$ littlewing --color --debug
Little Wing v0.4.0

> move e2e4
> show board
+---+---+---+---+---+---+---+---+
| 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 |
+---+---+---+---+---+---+---+---+
> show think
> time 1 10
> play
# using 0 threads
# FEN rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1
# allocating 10000 ms to move
# starting search at depth 1
 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      1       860  1. ... Nc6 2. Nc3 Nf6 3. Nf3
   4     -31      1      2435  1. ... d5 2. exd5 Qxd5 3. Nc3
   5     -32      2      4559  1. ... d5 2. exd5 Qxd5 3. Nc3 Qd4
   5     -21      2      7708  1. ... d6 2. Qe2 Nf6 3. Nc3 Nc6
   5      -3      3     11522  1. ... e5 2. Qh5 d6 3. d3 Nc6
   5       1      4     13090  1. ... Nc6 2. Nc3 Nf6 3. Nf3 d5
   6     -21      4     14191  1. ... Nc6 2. Nc3 Nf6 3. Nf3 d5 4. d3
   7      -7     10     42921  1. ... Nc6 2. Nf3 Nf6 3. e5 Ng4 4. d4 d5
   8     -30     15     68987  1. ... Nc6 2. Nf3 Nf6 3. Nc3 e6 4. d4 d5 5. e5
   9     -18     42    203216  1. ... Nc6 2. d4 d5 3. exd5 Qxd5 4. Nf3 Qe4+ 5. Be3 e5
  10     -43     68    337369  1. ... Nc6 2. d4 e6 3. Nc3 d5 4. Nf3 dxe4 5. Nxe4 Nf6 6. Bg5
  10     -38    113    570619  1. ... d5 2. exd5 Qxd5 3. Nc3 Qe6+ 4. Nge2 Nf6 5. d4 Nc6 6. Bf4
  10     -21    136    689628  1. ... e5 2. Nc3 Nf6 3. Nf3 Nc6 4. Bb5 Qe7 5. d3 d6
  11      -8    244   1231372  1. ... e5 2. c4 Bd6 3. Nf3 Ne7 4. Nc3 Nbc6 5. d4 O-O 6. c5 exd4
  12     -22    488   2552398  1. ... e5 2. Nf3 Nf6 3. Nc3 Nc6 4. d4 exd4 5. Nxd4 d5 6. exd5 Nxd5
  13     -13    859   4716253  1. ... e5 2. Nf3 Nf6 3. Nc3 Nc6 4. d4 exd4 5. Nxd4 d5 6. exd5 Nxd5 7. Bc4 Qe7+
# score:               -22
# time:               9951 ms
# nodes:           5571362 (5.60e5 nps)
# tt size:          524288 (8 MB)
#  - lower:         382039 (72.87 %)
#  - upper:          54669 (10.43 %)
#  - exact:            170 (0.03 %)
# tt inserts:       941233
# tt lookups:      3650051
#  - miss:         1472020 (40.33 %)
#  - hits:          469768 (12.87 %)
#  - collisions:   1708263 (46.80 %)
< move e7e5
+---+---+---+---+---+---+---+---+
| 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 |
+---+---+---+---+---+---+---+---+
> help
Commands:
  quit                      Exit this program
  help                      Display this screen
  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
  load <fen>                Set the board to <fen>

  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                     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 2014-2017 by Vincent Ollivier <v@vinc.cc>

Report bugs to https://github.com/vinc/littlewing/issues
> quit

Test

Unit testing in Rust is wonderful. You can run the test suite directly from Cargo:

$ cargo test

Little Wing also have a perft command for counting the number of nodes at each depth from the starting position.

$ cargo run
Little Wing v0.4.0

> 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 -- --color
Little Wing v0.4.0

> 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 others like divide, setboard or testsuite:

$ cargo run -- --color
Little Wing v0.4.0

> 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.

Little Wing

Usage

Test

License