A UCI chess engine written in C++11.

Drofa started as fork of the Shallow Blue chess engine. My initial intention was to take weak, but stable and working chess engine and try to improve it, learning c++ along the way.

During my Drofa experiments huge chunk of knowlenge were received from:

• VICE chess engine and tutorials.
• Chessprogramming WIKI great place for all chessprogramming-related knowledge.
• Weiss chess engine, with clean and understandable implementations of complex features. Drofa use Weiss 1.0 LMP base reduction formulas. Althouth Adagrad tuning implementation is not copy-pasted from Weiss, Drofa implementation closesy follows Weiss logic and can be considered a c++ rewrite of it.
• Several open source engines, mostly Ethereal and Stockfish

Special thanks to:

• Terje Kirstihagen (Weiss author)
• Andrew Grant. AdaGrad paper and Ethereal chess engine are great sources of knowledge; Ethereal tuning dataset was a great help in tuning. As well as allowing me on main OpenBench instance
• Kim Kahre, Finn Eggers and Eugenio Bruno (Koivisto team) for allowing Drofa on Koi OpenBench instance and motivating me to work on the engine
• OpenBench community for helping me in finding bugs, teaching me (even if unknowingly) good programming practices and interesting discussions

Drofa 1.0.0 64-bit    2061
Drofa 2.0.0 64-bit    2458
Drofa 3.0.0 64-bit    2891
Drofa 3.1.0 64-bit    2968
Drofa 3.2.0 64-bit    ????

Historically Drofa scales a bit better in LTC.

With Drofa 3.0 many features was added on top of the Shallow Blue, adding up to ~1000 elo.

Almost-full changelog with elo-gains measured for some of the features can be found:

• ShallowBlue -> Drofa 1.0.0 in the Drofa_changelog file.
• Drofa 1.0.0 -> Drofa 2.0.0 in the Drofa_changelog_2 file
• Drofa 2.0.0 -> Drofa 3.0.0 in the Drofa_changelog_3 file
• Drofa 3.0.0 -> Drofa 3.1.0 in the Drofa_changelog_4 file
• Drofa 3.1.0 -> Drofa 3.2.0 in the Drofa_changelog_5 file

make

If you have Mingw-w64 installed, you can cross compile for Windows on Linux with:

./build_windows.sh

WARNING - migw-w64 compiles are ~50% slower than native windows compiles, for best performance, use native windows g++ compiler.

Shallow Blue's code was extensively documented with Doxygen. I tried to follow this rule in the Drofa, and mostly sucseeded.

To generate HTML documentation use:

doxygen

Drofa 3.0.0 supports following UCI commands:

• BookPath
• OwnBook
• Threads (1 to 172),
• Hash (16 to 65536)

These options can be set from your chess GUI or the UCI interface as follows:

setoption name OwnBook value true
setoption name BookPath value /path/to/book.bin

These commands can be useful for debugging.

• bench
  • runs search on the list of positions and returns count of nodes searched and speed
• printboard
  • Pretty prints the current state of the game board
• printmoves
  • Prints all legal moves for the currently active player

I dont know shit about licensing and Drofa is too weak to be plagiarised. So it is under the same MIT license as Shallow Blue.

2017 - 2019 © Rhys Rustad-Elliott (original Shallow Blue creator)

2020 - 2021 © Litov Alexander