66 lines
2.2 KiB
Markdown
66 lines
2.2 KiB
Markdown
# gambit
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A chess engine written in Scala 3, built with [scala-cli](https://scala-cli.virtuslab.org/).
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## Overview
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`gambit` is a from-scratch alpha-beta chess engine. It uses a `0x88`
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mailbox board representation, Zobrist hashing for transposition detection,
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and a principal-variation search with a full set of modern pruning and
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move-ordering heuristics. It speaks the UCI protocol and can also read and
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write SAN, PGN and EPD.
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## Features
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- **Board** — `0x88` mailbox representation with incremental Zobrist hashing.
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- **Move generation** — pseudo-legal and legal generation for all piece
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types, including castling, en passant and promotions, validated by a
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`perft` node counter.
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- **Evaluation** — tapered midgame/endgame evaluation with piece-square
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tables, pawn structure (passed, doubled, isolated), mobility, the bishop
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pair, rook file bonuses and king safety, plus a static exchange
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evaluation (SEE).
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- **Search** — iterative-deepening PVS with quiescence search, a
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transposition table, null-move pruning, reverse futility and razoring,
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late-move reductions, late-move pruning, killer moves and a history
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heuristic, with aspiration windows at the root.
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- **Time management** — UCI `go` limit parsing (clock, increment,
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`movestogo`, `movetime`, `depth`, `infinite`) with a per-move budget.
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- **Notation** — SAN formatting/parsing, PGN reading/writing, and EPD
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parsing with a test-suite runner (bundled Win at Chess positions).
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- **Self-play** — a game loop with draw adjudication (fifty-move,
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insufficient material, threefold repetition).
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## Usage
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```sh
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# UCI mode
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scala-cli run . -- uci
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# self-play a game (maxPlies, depth)
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scala-cli run . -- selfplay 200 6
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# perft / search on a position
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scala-cli run . -- <fen|startpos> <depth>
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# run the EPD (Win at Chess) suite, N ms per position
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scala-cli run . -- epd 500
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```
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Running with no arguments prints usage and a short perft/search demo.
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## Tests
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```sh
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scala-cli test .
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```
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Tests use [munit](https://scalameta.org/munit/) and cover move generation
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and perft, make/unmake and hashing, evaluation and SEE, search heuristics,
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the transposition table, draw detection, SAN/PGN notation, time control and
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the UCI handler.
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## Requirements
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- scala-cli (Scala `3.8.4`, as pinned in `project.scala`)
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