Stockfish 18

Official release version of Stockfish 18

Bench: 2050811

---

Stockfish 18

Today, we have the pleasure of announcing Stockfish 18, a new major release. As
always, you can freely download it at [stockfishchess.org/download][1] and use
it as a drop-in replacement in the [GUI of your choice][2] to benefit from
stronger play and more accurate analysis.

Whether you can spare hours or days of CPU time, your help matters for the
ongoing development of Stockfish. Find out how you can help at
[stockfishchess.org/get-involved][3]. Join our [Discord server][4] to get in
touch with the community of developers and users of the project!

Quality of chess play

In tests against Stockfish 17, this new release brings an Elo gain of up to [46
points][5], and wins [four times as many game pairs][6] as it loses. Quality
improved throughout, including in [Fischer Random Chess][7].

Stockfish is stronger than any human, even when running on older or low-end
hardware. On the highest-end hardware, where Stockfish can search over [500
million positions per second][8], it continues to [dominate chess engine
tournaments][9].

Update highlights

Next-Generation Evaluation

This release introduces the SFNNv10 network architecture. The network’s input
layer has been augmented with 'Threat Inputs' features as part of a massive
community effort. These features allow the engine to 'see' which pieces are
threatened more naturally, resulting in more accurate evaluations.

Hardware and Performance Optimizations

A key highlight is the new 'Shared Memory' implementation, which allows
different Stockfish processes to share the same memory space for neural network
weights. This makes it the most efficient version for cloud analysis and
high-concurrency testing.

Significant efforts have also been made to utilize hardware more effectively by
adapting the code to make use of modern CPU instructions and refining how
threads interact during a search.

Search Improvements

Stockfish 18 features a heavily refined search, utilizing 'Correction History'
to dynamically adjust evaluations based on patterns found during the search
itself. These and other refinements allow the engine to detect stalemates and
evaluate fortresses significantly better than previous versions. A particularly
rare issue, involving threefold repetition detection, en passant, and pins, was
also fixed.

Refactored Training Workflow

The training of Stockfish's neural networks has transitioned to an automated
and reproducible model. This new framework allows the project to employ
standardized recipes to chain complex training stages together. This transition
facilitates the training of networks using over 100 billion positions of [Lc0
evaluation data][10].

Thank you

In this release in particular, we are deeply grateful to the contributors who
shared their research and ideas to help develop the new threat-input network
architecture.

The Stockfish project builds on a thriving community of enthusiasts (thanks to
everybody!) who contribute their expertise, time, and resources to build a free
and open-source chess engine that is robust, widely available, and very strong.

We would like to express our gratitude for the [14.6k stars][11] that light up
our GitHub project. Thank you for your support and encouragement – your
recognition means a lot to us. Programmers can contribute to the project either
directly to [Stockfish][12] (C++), to [Fishtest][13] (HTML, CSS, JavaScript,
and Python), to our trainer [nnue-pytorch][14] (C++ and Python), or to our
[website][15] (HTML, CSS/SCSS, and JavaScript).

The Stockfish team

[1]: https://stockfishchess.org/download
[2]: https://official-stockfish.github.io/docs/stockfish-wiki/Download-and-usage.html#download-a-chess-gui
[3]: https://stockfishchess.org/get-involved/
[4]: https://discord.gg/GWDRS3kU6R
[5]: https://tests.stockfishchess.org/tests/view/696a9e15cec152c6220c1d19
[6]: https://tests.stockfishchess.org/tests/view/696a9e4dcec152c6220c1d1b
[7]: https://tests.stockfishchess.org/tests/view/696a9e83cec152c6220c1d1d
[8]: https://openbenchmarking.org/test/pts/stockfish
[9]: https://en.wikipedia.org/wiki/Stockfish_(chess)#Competition_results
[10]: https://lczero.org/blog/2021/06/the-importance-of-open-data/
[11]: https://github.com/official-stockfish/Stockfish/stargazers
[12]: https://github.com/official-stockfish/Stockfish
[13]: https://github.com/official-stockfish/fishtest
[14]: https://github.com/official-stockfish/nnue-pytorch
[15]: https://github.com/official-stockfish/stockfish-web

Author: vondele

src/misc.cpp

@@ -40,7 +40,7 @@ namespace Stockfish {
 namespace {
 
 // Version number or dev.
-constexpr std::string_view version = "dev";
+constexpr std::string_view version = "18";
 
 // Our fancy logging facility. The trick here is to replace cin.rdbuf() and
 // cout.rdbuf() with two Tie objects that tie cin and cout to a file stream. We