Yavalath

This is an engine and AI player for the Yavalath 2-player board game. The goal is to form 4-in-a-row without first forming 3-in-a-row.

The game has 61 hex tiles, and internally the game state is represented using a pair of 64-bit bitboards, one for each player. The rules are encoded as two bit mask tables, and detecting wins and losses is just a handful of bit operations.

The AI has an API, documented in yavalath.h, and can be plugged into a variety of interfaces. For embedding, consider using the amalgamation build (make amalgamation), which will reduce the AI sources to one source file (yavalath.c) and won't require an intermediate build program.

For a user interface, only a minimal, crude CLI is available since the focus is on creating an AI player. The input must be in Susan notation. For example, the upper-left tile is a1 and the bottom-right tile is i5.

       1 2 3 4 5
    a . . . . . 6
   b . . . . . . 7
  c . . . . . . . 8
 d . . . . . . . . 9
e . . . . . . . . .
 f . . . . . . . . 9
  g . . . . . . . 8
   h . . . . . . 7
    i . . . . . 6
       1 2 3 4 5

The AI is a UCT Monte Carlo tree search and it's a decent player. However, it suffers from UCT's "shallow trap" problem and can easily be defeated once you recognize its blind spots.