Elixir Chess Engine

Elixir is a UCI-compliant chess engine developed in C++. It is the successor of my previous engine, Shuffle, and is under development with the goal of achieving an ELO rating of 3500+

Instructions to build

Building Elixir requires Make and latest versions of clang++ or g++ with C++20 support

make CXX=<compiler>

• Replace <compiler> with your preferred compiler - either clang++ or g++
  • If not specified, the compiler defaults to clang++
• Upon successful compilation, the binary file will appear in the root directory as elixir or elixir.exe depending on your operating system
  • You can also give a custom name to the binary by specifying it as EXE=<name> during compilation

Alternatively, you can download pre-compiled binaries from the Releases page

UCI Options

Name	Type	Default value	Valid values	Description
Hash	integer	64	[4, 1024]	Memory allocated to the Transposition Table (in MB).
Threads	integer	1	1	Number of Threads used to search.

Features

• Search : Standard PVS with Quiescence Search and Iterative Deepening
  • Aspiration Windows Search
  • Check Extension
  • Repetition Draw Detection
  • Mate Distance Pruning
  • Transpotition Table (TT) cutoff
  • Internal Iterative Reduction
  • Razoring
  • Reverse Futility Pruning
  • Null Move Pruning
  • Late Move Pruning
  • Futility Pruning
  • Static Exchange Evaluation (SEE) Pruning
  • Late Move Reductions
• Move Ordering
  • TT Move ordering
  • Good and Bad Captures ordering using SEE
  • Killer Move Ordering
  • Counter Move History
  • Butterfly History Move Ordering with maluses
• Evaluation : Hand Crafted Evaluation (HCE) using texel-tuned values
  • Tapered Evaluation
  • Material + Piece Square Table Evaluation
  • Piece Mobility Evaluation
  • Stacked Pawn Penalty
  • Bishop Pair Bonus
  • Passed Pawn Bonus
  • Rook Open & Semi-Open File Bonus
  • Tempo Bonus

Acknowledgements

• A special thanks to Ciecke, Zuppa, Yoshie, Shawn, A_randoomnoob, Gabe and everyone else on the StockFish Discord server for their continuous help in developing and bug-fixing Elixir.
• This project would never have been where it is right now, if it was not for the help of everyone on my OpenBench instance - Aron, Yoshie, Shawn, Mid. Massive CPU time donations by these guys is what enabled me to heavily test and tune Elixir.
• Andrew Grant for developing the OpenBench platform.