A small command-line utility for generating chess endgame positions that are particularly good at exposing chess engine bugs involving the 50-move rule.
Only-move-generator utilizes syzygy endgames tablebases to generate positions where there is only move that wins within the 50-move rule, or one move that saves the draw due to the 50-move rule. Additionally, every position will also have a move that misses the win/draw by one move, and will have at least 10 ply until the 50-move reset.
In tablebase terms, every position generated is either:
- A win with exactly one winning move, and one or more moves that lead to a cursed win.
- A blessed loss with exactly one drawing move, and one or more moves that lead to a true loss.
Binaries are available for 64-bit Windows and Linux, under releases. For other platforms, see the Compiling section.
The tool can generate positions with 3-7 pieces, depending on which tablebase you have installed. It requires a full set of syzygy tablebases, both wdl and dtz, including the tablebases for less than n pieces. They can be downloaded from a variety of sources, including https://syzygy-tables.info/.
Storing the tablebases on an SSD is significantly faster.
only-move-generator [-n <number of pieces>] <syzygypath>...
Note that it may not start outputting results immediately.
The resulting positions are continuously written to standard output in Extended Position Description for as long as the program runs. It includes hmvc (half-move counter), bm (best move) and ce (centipawn evaluation) tags. Centipawn evaluation will always be either 0 (blessed loss) or 10000 (win).
Example output, using 6-man tablebases:
2k1K3/2r5/8/R7/8/4n3/2n5/8 b - - hmvc 76; bm Nd4; ce 10000
4rk2/8/1n6/8/6PK/1N6/8/8 b - - hmvc 86; bm Nc4; ce 10000
8/K7/B1k5/7R/8/2q5/8/3n4 w - - hmvc 78; bm Rh6; ce 0
8/8/8/8/kb3R2/6K1/n7/4R3 b - - hmvc 78; bm Nc3; ce 0
k5n1/8/r7/5R2/8/b3K3/8/8 b - - hmvc 66; bm Kb7; ce 10000
Compiling requires a Rust compiler. The project has dependencies hosted on crates.io, so using cargo (Included in a rustup install) is strongly recommended.
cargo build --release
This will create an executable in target/release/.
This project is licensed under the GPLv3 (or any later version at your option). See the LICENSE.md file for the full license text.