I have been looking forward to reviewing the Rodent Chess Engine ever since its programmer Pawel Koziol informed me on my Facebook page about its release.

And I must admit that I was honored to be approached by the programmer of an engine I already liked to review his new offering and so I downloaded the Rodent II package within minutes.

What a nerd I am! 😛

At the time I was using the Fritz GUI for my engine testing and due to some issues within the GUI, was unable to use Pawel’s included personalities for my testing (Fritz GUI sucks for engine tweaking).

This really pissed me off, but since Pawel had mentioned that Rodent II was designed to be a “highly tweakable” release, I decided to create my own personality/s.

This Chess Engine Review is the result. 🙂

So…Just like DisasterArea 1.54, Rodent II’s raw, non-tweaked engine is 2800+ on the CCRL rating scale, which is pretty damn strong and too strong for a player like me (or most players) to play training games with.

So after tweaking it in the way I liked, I thought I had something worth training with…

THEN, I thought it was too weak and re-tweaked…

THEN, I still thought it was too weak and re-tweaked again…

NOW, I was happy.

It turns out NONE of them were too weak (the first one plays beautifully, actually!) and all three have similar, but still quite distinct playing styles which I like very much.

I threw them in a tournament in which I was researching the opening position reached after

1. d4 d5 2. c4 e6 3. Nf3 c5 4. cxd5 exd5 5. Nc3 Nf6 6. g3 Nc6 7. Bg2 Be7 8. O-O
O-O 9. dxc5 d4 10. Na4

Tarrasch Na4

This is an opening variation (and position the engines in the tournament began to “think” from) I had been researching as a possible addition to my own repertoire against 1.d4 and which offers equal chances and attacking possibilities if black chooses to play in such a manner.

There are several possibilities for black here:

10…Be6 (logical)

10…Bf5 (with ideas of …Be4 or …Qd7 and …Bh3 ideas)

and the ULTRA aggressive exchange sacrifice idea which is…

10…b5!!?!?!!?! (and has a critical line going 11. cxb6 axb6 12. Nxd4 Nxd4 13. Bxa8 Ba6 with a wild position)


The tournament was eventually won by a famous engine (to computer chess nerds) Thinker 5.3b Inert (2846), followed by Frenzee (2720) but when evaluating performance against other CCRL rated engines in this tournament our Rodent II personalities earned the following ratings:

Rodent II Henny: 2401 CCRL

Rodent II Remy: 2478 CCRL

Rodent II Alize: 2529 CCRL

Wow! So based on what we see above we can make the following conclusions.

  1. I named the personalities after my favourite brands of cognac…check!
  2. The engines got progressively stronger with each unsatisfied “tweak”…check!
  3. Style has been maximised while weakening the engine to a good level for training games…checkmate!

This is great news!

Now I have three new training partners with beautiful chess styles who I can play training games with, plus have help me analyze my games and openings with.

Let’s see how each personality dealt with our critical opening line above.

Rodent II Henny:

Rodent II Henny played in a logical and human way, preferring the 10…Bf5 and 11…Qd7 plan and attacking the kingside in this way.

Here are some games where he broke through with fantastic  style using this plan.

So needless to say, Rodent II Henny plays beautiful chess, right?

Let’s have a look at one of his brothers.

Rodent II Remy:

Although he varied his preference in the tournament, Rodent II Remy was a bit more ambitious than his brother Henny and usually went for the crazy sacrificial line beginning with 10…b5!?.

Here are some nice examples of his play in this line.

A similar, yet distinct style of play, right? So awesome! 🙂

Now let’s see the younger, stronger brother Rodent II Alize.

Rodent II Alize

This is the personality I finally settled upon. The final “tweak” we might say.

The personality which worked out to be the strongest, while still keeping some of his brother’s raw aggression and violent tendencies haha.

Rodent II Alize quite surprisingly (to me at least) was also a fan of the 10…b5!? line, and played a number of beautiful attacking games.

Here are a couple of them.

So I’d say we’ve done pretty well.

The three Rodent Cognac brothers (Henny, Remy and Alize) are fantastically talented attackers sure to give me tons of headaches in the future training games.

If YOU would like to take these guys on (or have them play engine matches), here are the settings.

Rodent II Henny (2401 CCRL Approx):

rodent II henny settings

rodent II henny settings

Rodent II Remy (2478 CCRL Approx):

rodent II remy settings

rodent II remy settings

Rodent II Alize (2529 CCRL Approx):

rodent II alize settings

rodent II alize settings

Where to get the engine?

Go to Pawel’s site and download it!

Which GUI to use?

Arena is the most stable interface for engine testing, tweaking and playing against chess engines.

Get it here.


This engine (of which I might make a fourth personality in future) is awesome and really impressive in its handling of positions where one side has the initiative or attacking chances.

It is non-materialistic and aggressive which is a big plus and I think it will make an excellent training partner.

Humanness of style: 9/10

Attractiveness of style: 10/10

Usefulness for analysis: Good for creative ideas in sharp openings.

Estimated ELO: 2300

Note: I have entered Rodent II Henny in my recent rapid tournament (in which I will play) so if you want to check out how he does, click here to follow the tournament!