Pulse Chess is a simple chess engine with didactic intentions in mind. The source code should be easy to read, so that new developers can learn, how to build a chess engine. If you want to roll your own, just fork it and start coding! :)

Pulse Chess is available in Java and C++. Both editions have the same feature set. The Java Edition requires Java 7 for compilation and execution. The C++ Edition is written in C++11. It has been compiled successfully using g++ 4.9.1 and Visual C++ 2013.


Only a couple of basic chess engine features are implemented to keep the source code clean and readable. Below is a list of the major building blocks.

  • UCI compatible
    Java Edition: Pulse Chess uses JCPI for implementing the UCI protocol.
  • 0x88 board representation
    To keep things simple Pulse Chess uses a 0x88 board representation. In addition piece lists are kept in Bitboards.
  • Only material and mobility evaluation
    Currently only material and mobility (to add some variation) are used for calculating the evaluation function. However it should be quite easy to extend it with other evaluation features.
  • Using integers for type representation
    Java Edition: Although Java is quite efficient and fast in memory management, it is not fast enough for chess engines. Instead of using objects for important data structures, Pulse Chess uses integers to exploit the Java stack.
  • Pseudo-legal move generator
    To keep the source code clean and simple, a pseudo-legal move generator is used. This has the advantage to skip writing a complicated legal move checking method.
  • Basic search
    Pulse Chess uses a basic Alpha-beta pruning algorithm with iterative deepening. This allows us to use a very simple time management. In addition there’s a basic Quiescent search to improve the game play.

Hack it

Pulse Chess can hold its own against an average club player. If you want to make it even better, have a look at the following ideas.

  • Null Move Pruning
    This will make you faster. A whole lot faster! If done right, it should give you quite a boost.
  • Transposition Table
    Although a little bit tricky to get right from the beginning, this technique can make you impressively faster.
  • Check Extensions
    This is the one extension I would choose first to implement. If you can control the search explosion, the tactical gain is awesome.
  • Passed Pawn
    This will definitely improve your endgame.
  • Staged move generation
    Tune your move generation! Don’t generate every move upfront. Believe me, you will get a nice speed increase.