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Princhess - development version with MCTS

Princhess is an interesting chess engine by a programmer with the nice nickname princesslana. It is a free open source chess engine using the UCI protocol. It is written in the Rust language and is released under two licenses: MIT and GNU GPL3.0. The initial code base was Sashimi.

What makes the Princhess engine different is its use of the MCTS (Monte-Carlo Tree Search) algorithm.

99% of chess engines use the Alpha-Beta algorithm, but there are exceptions. The most recognized is Lc0, which can play beautiful and extremely powerful chess. Another well-known one is Dragon by Komodo Chess, which is able to beat most Alpha-Beta opponents using MCTS.

Princhess is not (yet) such a strong chess engine, which makes it an interesting alternative to competing with human chess players :)

I would add that engines using MCTS usually play chess... naturally from my - human - point of view. I encourage you to check it out !

Here's how Princhess dealt with me when I wasn't very focused on the game....

In contrast, in the game below, with a literal real Chesstiger9 against me, despite my concentration I failed to find a beautiful tactical strike. This is a game played in mid-January 2023 on the PlayChess server.

In the position shown, the forcing mate is led by Qe6+ and the sacrifice of Rook on h6 in the next move.

Me not being a grandmaster and having seconds to make a move, I did not find the best continuation. Princhess didn't manage it either.

According to my tests on a MacBook Pro M1 with a short time to think, after playing 300 games Princhess plays with a strength of around 2350 Elo; equivalent to the playing strength of a human Chess Master.

Source: MCERL (ongoing)

Undoubtedly, at the current level, Princhess is not the best engine for chess analysis. On the other hand, the style of play is a factor in favor of giving Princhess a chance as a sparring partner or when struggling against engines at a similar level.

An impressive tactical strike!

Princhess can also be played via a web browser on the lichess server, where it has reached a ranking of 2093 Elo.



  1. Although the source code and compilations are as of 2023-01-22, the Princhess engine reports itself as: Princhess 0.0.0-dev.

  2. This is a development version of Princhess, so it may affect the stability of this chess engine on your computer. Darius, the author of this post, during testing, did not encounter any problems.

Feel free to download Princhess.

Linux, Mac and Windows – Compiled by Darius

Download 7Z • 8.85MB
Download 7Z • 8.24MB
Download 7Z • 4.06MB

Source code – by princesslana

Download 7Z • 38.00MB



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