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BrainLearn is a free, powerful UCI chess engine derived from BrainFish ( It is not a complete chess program and requires a UCI-compatible GUI (e.g. XBoard with PolyGlot, Scid, Cute Chess, eboard, Arena, Sigma Chess, Shredder, Chess Partner or Fritz) in order to be used comfortably. Read the documentation for your GUI of choice for information about how to use Stockfish with it.


This distribution of BrainLearn consists of the following files:

  •, the file you are currently reading.
  • Copying.txt, a text file containing the GNU General Public License version 3.
  • src, a subdirectory containing the full source code, including a Makefile that can be used to compile BrainLearn on Unix-like systems.

UCI parameters

BrainLearn hash the same options as BrainFish, but it implements a persisted learning algorithm, managing a file named experience.bin.

It is a collection of one or more positions stored with the following format (similar to in memory Stockfish Transposition Table):

  • best move
  • board signature (hash key)
  • best move depth
  • best move score

This file is loaded in an hashtable at the engine load and updated each time the engine receive quit or stop uci command. When BrainLearn starts a new game or when we have max 8 pieces on the chessboard, the learning is activated and the hash table updated each time the engine has a best score at a depth >= 4 PLIES, according to Stockfish aspiration window.

At the engine loading, there is an automatic merge to experience.bin files, if we put the other ones, based on the following convention:



  • fileType="experience"/"bin"
  • qualityIndex , an integer, incrementally from 0 on based on the file's quality assigned by the user (0 best quality and so on)


Because of disk access, to be effective, the learning must be made at no bullet time controls (less than 5 minutes/game).

Opening variety

Integer, Default: 0, Min: 0, Max: 40 To play different opening lines from default (0), if not from book (see below). Higher variety -> more probable loss of ELO

Terms of use

BrainLearn is free, and distributed under the GNU General Public License version 3 (GPL v3). Essentially, this means that you are free to do almost exactly what you want with the program, including distributing it among your friends, making it available for download from your web site, selling it (either by itself or as part of some bigger software package), or using it as the starting point for a software project of your own.

The only real limitation is that whenever you distribute BrainLearn in some way, you must always include the full source code, or a pointer to where the source code can be found. If you make any changes to the source code, these changes must also be made available under the GPL.

For full details, read the copy of the GPL v3 found in the file named Copying.txt.

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