Orange, A Xiangqi Chinese Chess Engine

Authors: Daniel Tan, Xiaofan Sun

This Xiangqi Chinese Chess Engine is named after the famous ancient Chinese manual "Secret of the Orange". This project has both a Xiangqi Graphical User Interface and a UCCI (Universal Chinese Chess Interface) protocol complaint Xiangqi Engine. This project supports Windows, Mac, and Linux.

Graphical User Interface Features

• Drag and Drop to move pieces
• Click to move pieces
• Psuedo Legal Move Generation
• Implements UCI (Universal Chess Interface) Protocol as well as UCCI (Universal Chinese Chess Interface)
• Can do human vs computer, computer vs computer
• Parse and load FEN strings
• Multi engine support
• UCI/UCCI Engine Options
• Windows, Mac, and Linux support
• Chess Clock with Increment
• Blindfold Mode
• Drawing Arrows with Right Click
• Display Engine Lines
• English/Chinese Language Options

Xiangqi Artificial Intelligence Engine

• Approximately 2560+ rating
• UCCI Protocol

Board Representation

• 90 square board
• Piece Lists
• Magic Sliding Bit Rows and Columns
• Pseudo Legal Move Generation
• Staged Move Generation

Threading

• Supports up to 256 Threads
• Lazy Shared Memory Processing Parallel Search

Search

• Negamax Search with Alpha Beta Pruning
• Principle Variation Search
• Iterative Deepening
• Aspiration Window Search

Pruning

• Reverse Futility Pruning
• Null Move Pruning w/ Endgame Verification
• Delta Pruning
• Razoring
• Mate Distance Pruning

Extensions

• Singular Search Extensions
• Check Extensions

Transposition Table

• 16-byte transposition table hash entries
• Zobrist Hashing with Incremental Update
• Prefetch Transposition Table Entries
• Depth Preferred + Random Replacement Scheme

Move Ordering

• Principle Variation Move Ordering
• MVV-LVA (Most Valuable Victim, Least Valuable Attacker)
• Killer Move Ordering
• Countermove Move Ordering
• History Move Ordering
• Countermove History Move Ordering

Evaluation

• Efficiently Updatable Neural Networks with Incremental Update
• 2 Layer Neural Network (2 x (1620 x 128) -> 1)
• Supports AVX2, SSE, and CPU without SIMD
• Trained on 40000 Grandmaster Games + 20000 Synthetic Games. 90 Million Positions

Repetition Rules

• 100% World Xiangqi Federation Repetition Rules Coverage
• Full Chasing Rule Coverage
• Understands Perpetual Check, Kill, Chase, Exhange, Block, Offer, Idle, etc.