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RubiChess 20230407. Elo: 3595 !

Clear #5 on MCERL.

This is not the official RubiChess logo

RubiChess is an open source chess engine by Andreas Matthies, written in C++, licensed under the GPL v3.0.

Source: MCERL (ongoing)

+28 Elo more than previous version !

We are talking about the developer's version; it is to be assumed that the official release will be even stronger!

A large increase in strength, which at this level should be received positively.

It is gratifying to see the growth in capabilities of this chess engine, showing that even at such a high level an increase of several dozen Elo points is as possible.

Thanks to author Mr. Andreas Matthies, RubiChess is a very friendly engine.

Compiling a working version for different operating systems - is a pleasure - in such a thoughtful way this process was simplified by the author.

In turn, the user, after running RubiChess on the command line, is informed by this chess engine whether he is using the best version.

An example of running RubiChess in the modern version (popcnt) on a computer supporting additional capabilities in the form of avx2 / bmi2. The engine informs about running a suboptimal binaries and suggests using another version.

On the same computer, after running RubiChess in the avx2 / bmi2 version, we see a message indicating that the selected binary is fully supported by the CPU of this computer.

If you would like to learn more about how to choose chess engine versions for your computer, I invite you to the How-To section.

*Here is a sample of the capabilities of latest RubiChess.

White: RubiChess 20230407, Black: Caissa 1.7


A position that does not herald such an imminent disaster for the blacks. Materially, the forces are aligned.

Is it possible to checkmate in such a position in 10 moves having an opponent playing with a strength above 3400 Elo ?

RubiChess can do it !


Caissa takes Pawn d4, threatening to play Rc8 in the next move.


RubiChess prevents Rook from playing to the c8 square, putting strong pressure on Bishop e7.


Black decides to strengthen the bound Bishop e7 through the King himself. Unfortunately for Caissa, bringing the King directly into the center of events in a situation with such strong pressure from white figures was not the best move.

Resistance could have been prolonged by 27...Bxa3 accepting to give up the Rook for the Bishop.


Black has a pawn more and... paralyzed figures.


Seemingly active Pawn play, which in addition reveals more of the black King's position.


RubiChess literally rules the chessboard. There are 5 moves left to checkmate the black King.


That's the power of chess bonding.

If 32...Qxb2 had occurred then in repose white takes the Rook with a 33.Qxd7.



Will the black King's escape help him ?


No. Double check and only 2 moves to checkmate.


Download ZIP • 3KB

Feel free to download RubiChess - true ruby gem among chess engines.

Linux ARM & Intel – Compiled by Darius

Download 7Z • 19.87MB
Download 7Z • 20.22MB

Mac Apple Silicon & Intel – Compiled by Darius

Download 7Z • 19.85MB
Download 7Z • 20.23MB

Windows – Compiled by Darius

Download 7Z • 20.71MB

Source Code – by Andreas Matthies

Download 7Z • 18.81MB


* Diagrams created in the ChessBase program.


Andreas Matthies
Andreas Matthies
Apr 08, 2023

Thanks for your kind words about my engine. I tested your Windows avx2 binary against my build and obviously my compiler setup is a little better than yours with 6.5% better speed:

Engine# (NPS) Speedup Sp Conf. 95% S.S.

2 (2.007.741,5 ) ---> 1 (1.885.236,0 ) ---> 6,498% 16.308,5 Yes No

My progress test was +22 Elo, so I'm very happy with your +28 Elo.

I'm running tests of one last Elo gainer now and will release something on monday probably.

Apr 08, 2023
Replying to

Thank you for getting back to me with a performance update of your build.

I appreciate the testing you've done and I'm glad to see RubiChess growing in strength like this. I'm also interested in the upcoming official release you mentioned and can't wait for it 😊

Thanks again for your post and for your hard work on the engine.

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