github.com/codedeliveryservice/Reckless @v0.9.0
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README
Reckless – Chess Engine in Rust
Reckless is a competitive chess engine, consistently performing among the top engines in major tournaments including Chess.com Computer Chess Championship (CCC) and Top Chess Engine Championship (TCEC).
Rating
| Version | CCRL Blitz | CCRL 40/15 | CCRL FRC | Release Date |
|---|---|---|---|---|
| Reckless v0.8.0 | 3765 +/- 14 [#2] | 3609 +/- 11 [#3] | 4077 +/- 13 [#3] | Aug 29, 2025 |
| Reckless v0.7.0 | 3500 +/- 12 [#68] | 3422 +/- 12 [#72] | Aug 23, 2024 | |
| Reckless v0.6.0 | 3386 +/- 15 [#95] | 3317 +/- 15 [#103] | Mar 22, 2024 | |
| Reckless v0.5.0 | 3240 +/- 17 [#133] | 3211 +/- 17 [#140] | Feb 4, 2024 | |
| Reckless v0.4.0 | 2934 +/- 17 [#210] | 2926 +/- 16 [#222] | Dec 13, 2023 | |
| Reckless v0.3.0 | 2616 +/- 19 [#297] | 2617 +/- 19 [#321] | Nov 6, 2023 | |
| Reckless v0.2.0 | 2349 +/- 18 [#406] | Oct 7, 2023 | ||
| Reckless v0.1.0 | 2005 +/- 18 [#539] | May 16, 2023 |
Getting started
Precompiled binaries
You can download precompiled builds from the GitHub Releases page.
-avx512: Fastest, requires a recent CPU with AVX-512 support-avx2: Fast, supported on most modern CPUs-generic: Compatible with virtually all CPUs, but significantly slower than AVX2 or AVX512 builds
[!NOTE] If you're unsure which binary to use, try the AVX-512 build first. If it doesn't run on your system, fall back to the AVX2 build, or the generic one as a last resort.
Building from source
To build Reckless from source, make sure you have:
Rust 1.88.0or a later version installed (official Rust installation guide)Clanginstalled (required for building the Fathom library used for Syzygy endgame tablebase support)
Once installed, you can build it with:
cargo rustc --release -- -C target-cpu=native
# ./target/release/reckless
To build without Syzygy tablebase support and Clang dependency, add the --no-default-features flag:
cargo rustc --release --no-default-features -- -C target-cpu=native
PGO builds
For profile-guided optimization (PGO) builds, you need to install additional tools:
rustup component add llvm-tools
cargo install cargo-pgo
Then, you can build the engine using make:
make pgo
# ./reckless
Or run the steps manually:
cargo pgo instrument
cargo pgo run -- bench
cargo pgo optimize
# ./target/x86_64-unknown-linux-gnu/release/reckless
# (the path may vary based on your system)
Usage
Reckless is not a standalone chess program but a chess engine designed for use with UCI-compatible GUIs, such as Cute Chess, En Croissant, or Nibbler.
UCI options
Reckless supports the following UCI options:
| Name | Default | Description |
|---|---|---|
| Hash | 16 | Size of the transposition table in MB [1–262144] |
| Threads | 1 | Number of search threads [1–512] |
| MultiPV | 1 | Number of principal variations to display [1–218] |
| UCI_Chess960 | false | Enable Chess960 (Fischer Random) support [false–true] |
| Minimal | false | Enable minimal UCI output [false–true] |
| MoveOverhead | 100 | Time in milliseconds reserved for overhead during each move [0–2000] |
| Clear Hash | — | Clear the transposition table |
| SyzygyPath | — | Path to Syzygy endgame tablebases |
Custom commands
Along with the standard UCI commands, Reckless supports additional commands for testing and debugging:
| Command | Description |
|---|---|
perft <depth> |
Run a perft test to count the number of leaf nodes at a given depth |
bench |
Run a benchmark on a set of positions to measure the engine's performance |
d |
Print the current board position in a human-readable format together with FEN |
eval |
Print the network evaluation of the current position from white's perspective |
compiler |
Print the compiler version, target and flags used to compile the engine |
Acknowledgements
- Code contributors who help develop and improve Reckless
- Hardware contributors providing compute resources
- OpenBench is the primary testing framework powered by Cute Chess
- Bullet is the NNUE trainer
- Stockfish, PlentyChess, and many other open source chess engines
- Members of the Stockfish Discord server
- Chess Programming Wiki
- CCRL and all chess engine testers out there
License
This project is licensed under the GNU Affero General Public License v3.0.
Extension points exported contracts — how you extend this code
Core symbols most depended-on inside this repo
Shape
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For agents
$ claude mcp add Reckless \
-- python -m otcore.mcp_server <graph>