protected MoveValuePair handleTerminal(Position position, boolean maxTurn, int alpha, int beta)
throws IllegalMoveException {
MoveValuePair finalMove = new MoveValuePair();
if (position.isTerminal() && position.isMate()) {
this.terminalFound = position.isTerminal();
finalMove.eval = (maxTurn ? BE_MATED : MATE);
} else if (position.isTerminal() && position.isStaleMate()) finalMove.eval = 0;
else {
finalMove.eval = quiescence(position, alpha, beta, !maxTurn);
}
// System.out.print(finalMove.eval + " ");
return finalMove;
}
@Override
protected MoveValuePair ABMaxMinValue(
Position position, int depth, int alpha, int beta, boolean maxTurn)
throws IllegalMoveException {
if (depth <= 0 || position.isTerminal()) {
return handleTerminal(position, maxTurn, alpha, beta);
} else {
MoveValuePair bestMove = new MoveValuePair();
LinkedList<MoveValuePair> sortedMoves = getSortedMoves(position, maxTurn);
for (MoveValuePair movepair : sortedMoves) {
short move = movepair.move;
// collect values from further moves
// get and update transposition table if possible
position.doMove(move);
if (this.p2tte.containsKey(position.getHashCode())
&& (this.p2tte.get(position.getHashCode()).depth >= depth)) {
// System.out.println("trans table at level: " + depth);
TransTableEntry tte = p2tte.get(position.getHashCode());
bestMove.updateMinMax(move, tte.eval, maxTurn);
} else {
// recursive method
MoveValuePair childMove = ABMaxMinValue(position, depth - 1, alpha, beta, !maxTurn);
bestMove.updateMinMax(move, childMove.eval, maxTurn);
p2tte.put(position.getHashCode(), new TransTableEntry(childMove.eval, depth, move));
}
position.undoMove();
// update the alpha beta boundary
if (maxTurn) alpha = bestMove.eval;
else beta = bestMove.eval;
// prune the subtree if needed
if (alpha >= beta) return bestMove;
}
return bestMove;
}
}