Rebel 14

This year (2022) it's 42 years ago I started chess programming, from REBEL 1.0 -> REBEL 12 and after my retirement from the competition and commerce (2003) the free hobby versions of ProDeo only gained about 200-250 elo through the years 2003-2021.

Inspiration (after 19 years) returned after a well known chess programmer offered his help with the implementation of the NNUE technique.

And the result speaks for itself, an improvement of 300-350 elo. It's my pleasure to realese REBEL 14, back to my brand name and its roots.

Rebel 14 is released under the GPLv3 licence.


Rebel 14 consists of 4 parts,

1. The famous Fruit 2.1 engine from 2004 by Fabien Letouzey, elo ~2700

2. Growing Fruit by Pawel Koziol improving the Fruit search, elo ~2800 making it about equal in strength with ProDeo 3.1

3. Replacing the Fruit evaluation with Benjamin 1.1 NNUE evaluation.

4. NNUE code to excecute the Benjamin NN evaluation by Chris Whittington.

NNUE evaluation, how it works, steps,

1. Playing millions of fast Benjamin 1.1 games.

2. Creating EPD's from the games.

3. Pruning the EPD's throwing out tactical positions.

4. Making sure you have enough positions left, typically 850 million for Rebel.

5. Put the 850 million into the learner which will create the nnue file.

The result is a blueprint of Benjamin's evaluation and playing style, only better and much stronger.


Playing style, wild and exciting as the title of the song.

At times a bit too aggressive making an unsound move. But Benjamin is the gambit version of the more balanced ProDeo 3.1 after all and so it is tolerable for a first version.

Next versions will focus on the playing style of ProDeo 3.1, there is a whole new world to explore anyway.

Results : 2 matches against an elo pool of 3100 elo rated engines.








Rebel 14






Gambit Positions GRL

Rebel 14






Gambit Positions GRL

This would put Rebel 14 on place 25 of the current Gambit Rating List.



  • Fabien Letouzey for Fruit 2.1 

  • Pawel Koziol for Growing Fruit

  • Chris Whittington for introducing me into NNUE, providing me with the necessary tools and writing the NNUE code.

Rebel 14

Source Code

There are 2 versions of Rebel 14

1. Rebel-14-avx2  for modern computers

2. Rebel-14-sse    for somewhat older computers.

Use Rebel-14-avx2 wherever possible since it runs

about 20% faster.