Chester

A chess library and engine written in Go.

Library Features

• Fast legal move generation using bitboards
• FEN (Forsyth–Edwards Notation) parsing and serialization
• Magic bitboard sliding piece attack lookup
• Zobrist hashing (Polyglot-compatible)
• Perft for move generation testing and benchmarking

Engine Features

• Universal Chess Interface (UCI)
• Negamax with Alpha-Beta pruning
• Tranposition Table
• Search time / nodes budget
• Iterative Deepening
• Quiescence search
• PeSTO evaluation function
• Opening book support (Polyglot .bin format)

Demo

Play against Chester in lichess.

Installation

go get github.com/bluescreen10/chester

Usage

As a library

import "github.com/bluescreen10/chester"

// Parse a position from FEN
pos, err := chester.ParseFEN(chester.DefaultFEN)
if err != nil {
    panic(err)
}

// Generate legal moves
var moves []chester.Move
moves, inCheck := chester.LegalMoves(moves, &pos)

// Apply a move
pos.Do(moves[0])

// Serialize back to FEN
fmt.Println(pos.FEN())

// Perft
results := chester.Perft(&pos, 6)
var nodes int
for r := range results {
    nodes += r.Count
}
fmt.Printf("nodes: %d\n", nodes)

As an engine (UCI)

go run ./cmd

position startpos
perft 6

a2a3: 4463267
b2b3: 5310358
c2c3: 5417640
d2d3: 8073082
e2e3: 9726018
f2f3: 4404141
g2g3: 5346260
h2h3: 4463070
a2a4: 5363555
b2b4: 5293555
c2c4: 5866666
d2d4: 8879566
e2e4: 9771632
f2f4: 4890429
g2g4: 5239875
h2h4: 5385554
b1a3: 4856835
b1c3: 5708064
g1f3: 5723523
g1h3: 4877234
perft 119060324 in 363.214708ms

(The above results were produced in a Macbook Pro M2)

References

• Chess Programming Wiki
• Magic Bitboards
• Polyglot Opening Book Format