dicechess.engine.movegen

Precomputed attack tables for leaping pieces (Knights and Kings).

Since leapers are not blocked by other pieces, their attacks can be completely pre-calculated at JVM startup for all 64 squares.

Legal moves filter for Dice Chess.

Implements the Maximum Micro-moves Rule: a player must choose a first move that is part of the longest possible sequence of micro-moves achievable with the rolled dice.

Two types of legal first moves

1. King-Capture — any sequence of micro-moves that ends with capturing the opponent's King is always legal, regardless of whether it is 1, 2, or 3 moves long.
2. Non-King-Capture — any sequence of micro-moves that does not end with a King capture must achieve the globally optimal length L*(state, dice).

Rules encoded here

• Normal move — consumes exactly one die of the matching piece type.
• Castling — requires and consumes both the King die (6) and the Rook die (4) simultaneously.
• King-Capture — terminates the game; a King capture contributes its depth to maxLen but is not recursed into (the game is over). All branches continue to be searched so that maxLen is computed correctly.
• Active-color invariance — the active color is kept fixed for every intermediate state produced during a turn; it is not toggled between micro-moves.

Magic Bitboards implementation for sliding pieces (Bishops and Rooks).

Magic Bitboards provide O(1) lookup for sliding piece attacks by hashing the current board occupancy into a precomputed attack table.

Unified move generator for Dice Chess. Coordinates between specialized generators for pawns, leapers, and sliding pieces.

Highly optimized pawn move generation using Bitboard arithmetic.

Unlike leaping pieces which are generated per-square, pawn pushes and attacks can be calculated in parallel for all pawns of a given color simultaneously using bitwise shifts.