KhetAI

An AI engine and multi-platform implementation for the board game Khet.

This project started as a Ruby gem and over time, new ways to interact with the core C code were built (see the Subprojects section below).

The core AI engine is written in C for performance and uses bit-packing, alpha-beta pruning, and Zobrist hashing. The code lives in the ext/khetai directory.

Example (via the Ruby gem):

require 'khetai'

# initial board setup:
# A = anubis, P = pyramid, S = scarab, X = pharaoh, L = sphinx
# capital letters = red, lowercase letters = silver
# numbers = 1 north, 2 east, 3 south, 4 west
board = ["L2", "--", "--", "--", "A2", "X2", "A2", "P1", "--", "--",
         "--", "--", "P2", "--", "--", "--", "--", "--", "--", "--",
         "--", "--", "--", "p3", "--", "--", "--", "--", "--", "--",
         "P0", "--", "p2", "--", "S2", "S3", "--", "P1", "--", "p3",
         "P1", "--", "p3", "--", "s1", "s0", "--", "P0", "--", "p2",
         "--", "--", "--", "--", "--", "--", "P1", "--", "--", "--",
         "--", "--", "--", "--", "--", "--", "--", "p0", "--", "--",
         "--", "--", "p3", "a0", "x0", "a0", "--", "--", "--", "l0"]

whose_turn = 1          # silver = 0, red = 1
max_search_depth = 25   # between 2 and 25
max_search_time = 5     # in seconds

move = KhetAI.move(board, whose_turn, max_search_depth, max_search_time)
#=> [start_index, end_index, rotation]
# rotation = 0 none, 1 clockwise, -1 counterclockwise

Uses SDL3 for its rendering and input processing. The laser is animated in real time using vector math and the pieces are all drawn with SDL_RenderGeometry calls. It also runs in the browser via WebAssembly, compiled with Emscripten.

Playable here: https://jkugs.github.io/

Located in the ext/khetai/dev/sdl-ui directory.

A C++ FLTK GUI that allows manual testing of the AI and gameplay. Supports live reloading of the AI during runtime using Shift + K.

Located in the ext/khetai/dev/fltk-ui directory.

$ gem install khetai

To build the gem from source, you'll need:

• Ruby >= 2.3.0
• GCC or compatible C compiler
• Development headers (usually provided by ruby-dev or ruby-devel package)

This project uses asdf as the version manager for Ruby. However, any Ruby version >= 2.3.0 should work to compile this gem.

$ gem install bundler
$ bundle install
$ bundle exec rake compile
$ bundle exec rake build
$ gem install pkg/khetai-<version>.gem

Once tested and verified, bump the version number in lib/khetai/version.rb, then run bundle install to update Gemfile.lock, and commit changes.

To release and push to rubygems.org:

$ bundle exec rake release

To push a pre-built gem manually:

$ gem push pkg/<gem>

To build and learn from... 🐢