Go chess engine, AI, cli interface, and websocket client ♞
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README.md

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go-chess || ghess

A Golang chess engine and user interfaces. Challenge the AI, Ghess, online.

|Move:  3     Turn: b
|Check: false Castle: KQkq
|Mate:  false Score: *
8: |♖||♘||♗||♕||♔|| ||♘||♖|
7: |♙||♙||♙||♙|| ||♙||♙||♙|
6: |░|| ||░|| ||░|| ||░|| |
5: | ||░||♗||░||♙||░|| ||░|
4: |░|| ||░||♟||♟|| ||░|| |
3: | ||░|| ||░|| ||♞|| ||░|
2: |♟||♟||♟|| ||░||♟||♟||♟|
1: |♜||♞||♝||♛||♚||♝|| ||♜|
   :a::b::c::d::e::f::g::h:
Black to move:

Instructions

ghess.go is a Go package responsible for representing a chess board, parsing PGN input, and validating moves. In the UI branch, in the ui/ directory, clichess.go is a simple interface for debugging and growser.go is a browser client powered by websockets. See godoc for the docs.

  • To use the package in a project, start a new game by calling ghess.NewBoard(), which returns an instance of the ghess.Board struct, ready to Board.ParseMove() and return FEN positions, Board.Position().

  • To use the built in Front-Ends, go to the UI branch:

    • To play a real-time game over the internal network, run growser.go within the /ui directory, and connect to port 8080.

    • After cloning the source into $GOPATH/src/github.com/polypmer/ghess/, try

      go run ui/clichess.go // found in UI branch

    • To see a math/rand vs math/rand game, enter into the clichess client:

      > /random-game

    • To evaluate a board position, with positive numbers as a White advantage and negative as Black advantage:

      > /eval

Basic Features and Functionality

  • Most rules are implemented:
    • Pawns only promote to Queen.
    • There is no PGN disambiguation for Queens.
  • PGN import-export via Board.LoadPgn() and Board.PgnString()
  • FEN import-export via Board.LoadFen() and Board.Position()
  • Command Line interface.
  • Web interface
  • Artificial intelligence, goes 5 ply in a few seconds.

Search and Evaluate Features

  • Looks for all possible and valid moves via Board.SearchForValid(), which returns two []int slices with the coordinates of possible origins and possible targets. The Board field pieceMap is a map[int]string; the aforementioned ints are keys for the standard notation coordinates.
  • Evaluation returns a score with a positive value for white advantage and negative value for black advantage. See the evaluation.go file for it's emerging api. There is also a Board.MoveRandom() method which passes in two []int slices and math/rand chooses a move.

Bitmap

The chess engine works with a 120 (10x12) bitmap []byte slice, stored in the Board board field. This boils down to (accessible with the /coordinates command in clichess.go):

Coordinates:
8: |88||87||86||85||84||83||82||81|
7: |78||77||76||75||74||73||72||71|
6: |68||67||66||65||64||63||62||61|
5: |58||57||56||55||54||53||52||51|
4: |48||47||46||45||44||43||42||41|
3: |38||37||36||35||34||33||32||31|
2: |28||27||26||25||24||23||22||21|
1: |18||17||16||15||14||13||12||11|
   :a ::b ::c ::d ::e ::f ::g ::h :
  • 11 - 18 1st rank
  • 81 - 88 8th rank

Road Map:

  1. FIXME: SearchForValid empassant
  2. FIXME: Horizon Effect
  • Keep track of capture state to combat horizon effect
  1. FIXME: Invalid fen when first Move number is not zero
  2. TODO: Change Board to Game
  3. TODO: Save history

Basic Functionality

  • Minor pawn promotion.
  • Queen disambiguation.
  • Checkmate should update PGN headers/history.
  • ParseMove should allow for resign.

User Interfaces

Clichess

  • A commandline chess program, it can output and parse PGN and FEN notation.
  • Type > /help to list options.

clichess

Growser

  • A server api using gorilla/websocket for live network chess playing!
  • Dependency: gorilla/websocket (BSD) and Chessboard.js (MIT)
  • NB. Castling is only when King steps on Rook, not like normals.
  • Games are stored with a BoltDB keystore database
  • See the repository: Shallow-Green

License

Copyright (C) 2016 Fenimore Love

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.