Update 12/3/2024, 20:02 UTC: Added v4 binaries for machines with avx512 support.

Estimated Rating: 3500 CCRL

Estimated EAS: 330k-450k (depending on the testing method)

Patricia 4 is now out! Thanks to a new net trained on Patricia data, a lot of search patches, and a bitboard rewrite, she's now able to compete much more effectively with top engines, while retaining her status as the most aggressive chess engine out there.

Explanation about the EAS value:

I measured an EAS score of 470,000 in my initial testing before release, however when Stefan Pohl tested it under his conditions he only got a score in the low 300 thousands. I've traced this discrepancy to the different books used in the testing, with Pohl using more unbalanced books than me. Pohl's EAS score is more likely to be accurate in engine games, meaning I have a lot of work to do EAS-wise, however I've held up the release long enough so the task of hiking up the EAS under top engine tournament conditions will be left to Patricia 4.1/5.

Patricia is still the most aggressive engine out there and is now far stronger than 3.1 was, able to fully hold its own in TCEC and CCC.

Binaries

Linux and Windows binaries are found below. Use v3 (avx2) for most computers, and use v2 (SSE) for very old models. If you're not sure about which one to download, try v3 first.

If you have a machine that supports AVX512 or you want to compile from source for other reasons, you can easily build Patricia from source by running the commands:

git clone https://github.com/Adam-Kulju/Patricia
cd Patricia/engine
make -B

The executable patricia will be found in the current directory, that is, Patricia/engine.

Acknowledgements

Gabe, the Obsidian author, is responsible for a majority of Patricia's Elo increase. I really appreciate his help and collaboration - the only reason he's not a coauthor is because he declined to be added as one.

Thank you to everyone who supports Patricia. I'm truly grateful for all the attention she's received.

A Note on Antivirus Software

I've been getting a lot of reports of antivirus software flagging Patricia as a virus. She is not a virus and this problem happens to most chess engines, but it's been especially annoying and persistent with her for some reason. If you're struggling with getting an executable due to this let me know and I'll see what I can do to help you out.