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Viridithas 8.0.0 - released & Championship Match.

The latest version of Viridithas 8 is about 100 Elo stronger than Viridithas 7.

According to MCERL, Viridithas 8 plays with a strength of 3372 Elo.

Source: GitHub

I love such surprises :)

Viridithas is a free and open source chess engine written in the Rust language. Published under the MIT License.

The author, Cosmo Bobak, who (as I wrote in a previous post about Viridithas) is obsessed with treesearch, has successfully used his "obsession" and is passionately developing his chess engine.

According to the latest results (MCERL ongoing), the strongest chess engine written in Rust is Velvet 5.1.0 with a ranking of 3377 Elo.

Viridithas, after playing 738 games, reached 3372 Elo, only 5 Elo less.

Source: MCERL (ongoing)

To decide which of these chess engines is stronger, I decided to play a match between them.

With 10, 50 or maybe 100 games? Nothing of the sort!

In the end, I wanted to determine the undisputed Champion – the strongest chess engine written in the Rust language participating in the MCERL competition.

Viridithas faced Velvet in the Championship match consisting of 300 games. Time: the same as in the MCERL competitions.

Here are the results:

Velvet won by 1 point. Only one :)

Well... with this dynamic growth of both these engines, the next match between this worthy rivals may end in a different result.

Games to download.

Download ZIP • 103KB

To be sure, the next versions of Viridithas and Velvet will be paired by me in what I hope will be a no less interesting match.

Ok, take a look at how Viridithas can play*.

White: Viridithas-8.0.0

Black: Bit-Genie-9, a robust chess engine that plays thickly above 3000 Elo.

Below we see an aligned position full of opportunities for both sides, created by playing the Spanish Opening.

White's Bishop seems to be somewhat stuck on the c2 field, while the black Knight has no freedom standing on the b7 field. In this type of position, it is not uncommon for one side to prepare and realize a breakthrough by playing Pawn to the f4 field (white) or the f5 field (black).


Is it too fast? After all, white, if the exchange takes place, will expose itself to a "fork" attack by playing the black pawn on g5.


And indeed, Bit-Genie does not hesitate to attack Viridithas two figures. So was white Pawn's previous move on f4 a mistake ?


At first glance, it's easy to come to a hasty conclusion. Viridithas, at the price of Knight, opened the F line for Rook, placed Bishop on the excellent d4 field and, in prospect, enabled the activation of his other figures.


Blacks are trying to create any chance of a constructive game for themselves. White calmly gives up the "brawl" on the Queen's wing.


The punch line of Viridithas' idea from a few moves ago is starting to become apparent. The exposed position of the black King does not bode well for Bit-Genie.

28. Qe4

In a little while, the King of the Blacks will have to evacuate.


The Black King's defenders can only look on.


Another sacrifice! How beautiful :) Viridithas brings his Knight into the center of events, offering black another of its figures, this time a white Bishop.


Black makes the only fat mistake of the game, taking the white Bishop off the d4 field. Bit-Genie desperately tries to do everything - reduces the material on the chessboard just to turn the game around.

What can white do in this position?

Dear reader, before you scroll down this page, think about white's next move.

Already ?

If so, let's see what Viridithas played in his 31st move.


What an impact! Another sacrifice made by white to get the black King on the chessboard.


Viridithas already has less material on Rook and Knight, but it still devotes its forces - this time attacking using Pawn.


Blacks with the last strength try to achieve anything, blocking the white Bishop. Will this help anything?


The last beautiful notes of this game resound. Double check to the black King.


The power of Viridithas calmness almost pulls me out of my shoes ;)

What a computer player, it moves its Bishop without haste to finally plunge Bit-Genie-9.


After a few moves, white gives the mat.

Download ZIP • 4KB

Viridithas wins in such style that I wonder if this game will be among the other contenders for game of the year :)

The new one - Viridithas 8.0.0 - and the style in which it plays impressed me. This is another engine created with the Rust language, whose style and level of play can evoke so many positive emotions and pleasant impressions when watching it in action.

I encourage you to download Viridithas 8.1.0.


(...) This release adds WLD probability-adjusted reporting to Viridithas. No strength difference exists compared to 8.0.0, but Viridithas's score cp output is now normalised such that 100 centipawns == 50% chance of winning, and Viri now outputs WDL probabilities per mill.


Source: GitHub

Android – Compiled by Archimedes

Download 7Z • 6.78MB

Linux arm64 & x64 – Compiled by Darius

Download 7Z • 5.59MB
Download 7Z • 6.66MB

Mac Apple Silicon & Intel – Compiled by Darius

Download 7Z • 4.91MB
Download 7Z • 5.70MB

Windows x64 – Compiled by Darius

Download 7Z • 5.62MB


* Diagrams generated in Aquarium program.

2 comentários

Edward Appleton
Edward Appleton
03 de abr. de 2023

Love seeing this improvement in Viridithas, however there is one small mistake that I have spotted. The author is named "Cosmo Bobak", not nicknamed.

04 de abr. de 2023
Respondendo a

Thank you for bringing it to my attention. I have corrected it.

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