private int GetBoardValueRecursive(OthelloBoard board, int ply,
int notStuck, int alpha, int beta)
{
//MyTrace(ply, "left="+board.EmptySquares+" alpha="+alpha+" beta="+beta);
/* If the game is over */
if (notStuck == 0 || board.EmptySquares == 0)
{
_finalEvaluations++;
int squareDifference = board.PlayerSquares - board.OpponentSquares;
if (squareDifference > 0)
{
return(squareDifference + 1000);
}
if (squareDifference < 0)
{
return(squareDifference - 1000);
}
// Tie
return(0);
}
#if USE_TRANSPOSITION_TABLE
int moveToTryFirst_X = -1, moveToTryFirst_Y = -1;
bool needToTryFirstMove = false;
int boardHashCode = board.GetHashCode();
int transpositionValue = _transpositionTable.LookupEntry(boardHashCode, ply,
alpha, beta, ref moveToTryFirst_X, ref moveToTryFirst_Y);
if (transpositionValue != AlphaBetaOthelloPlayer.INVALID_MOVE)
{
_transpositionHits++;
return(transpositionValue);
}
if (moveToTryFirst_X >= 0)
{
needToTryFirstMove = true;
}
TranspositionTableElementType elementType = TranspositionTableElementType.Alpha;
OthelloMoveWithData bestMove = null;
#endif
if (ply == 0)
{
_boardEvaluations++;
int val = GetBoardValue(board);
#if USE_TRANSPOSITION_TABLE
_transpositionTable.AddEntry(boardHashCode, 0, val,
TranspositionTableElementType.Exact, -1, -1);
#endif
return(val);
}
int count = 0;
for (int y = 0; y < 8; y++)
{
for (int x = 0; x < 8; x++)
{
OthelloMoveWithData move;
#if USE_TRANSPOSITION_TABLE
if (needToTryFirstMove)
{
move = board.GetMoveInfoIfValid(moveToTryFirst_X, moveToTryFirst_Y);
needToTryFirstMove = false;
// Set x to -1 to make sure that (0,0) gets process next time around
x = -1;
// This could happen if we found an incorrect entry in the table
if (move == null)
{
continue;
}
}
else
{
// Skip this move if we've already tried it
if (x == moveToTryFirst_X && y == moveToTryFirst_Y)
{
continue;
}
move = board.GetMoveInfoIfValid(x, y);
if (move == null)
{
continue;
}
}
#else
move = board.GetMoveInfoIfValid(x, y);
if (move == null)
{
continue;
}
#endif
count++;
/* perform the move */
board.PlayMove(move);
//MyTrace(ply, move.X + "," + move.Y + " alpha="+alpha+" beta="+beta);
int val = (-GetBoardValueRecursive(board, ply - 1, 2, -beta, -alpha));
//MyTrace(ply, move.X + "," + move.Y + " alpha="+alpha+" beta="+beta+" val="+val);
board.UnplayMove(move);
if (val >= beta)
{
#if USE_TRANSPOSITION_TABLE
_transpositionTable.AddEntry(boardHashCode, ply, beta,
TranspositionTableElementType.Beta, move.X, move.Y);
#endif
return(BEST_MOVE);
}
if (val > alpha)
{
alpha = val;
#if USE_TRANSPOSITION_TABLE
elementType = TranspositionTableElementType.Exact;
bestMove = move;
#endif
}
}
}
if (count == 0)
{ /* if no possible move */
board.SwitchPlayer();
int val = -GetBoardValueRecursive(board, ply, notStuck - 1, -beta, -alpha);
board.SwitchPlayer();
return(val);
}
#if USE_TRANSPOSITION_TABLE
if (bestMove != null)
{
_transpositionTable.AddEntry(boardHashCode, ply, alpha, elementType, bestMove.X, bestMove.Y);
}
else
{
_transpositionTable.AddEntry(boardHashCode, ply, alpha, elementType, -1, -1);
}
#endif
return(alpha);
}
public override PlayerResult GetMove(OthelloBoard board)
{
StringBuilder statusString = new StringBuilder();;
_finalEvaluations = 0;
_boardEvaluations = 0;
#if USE_TRANSPOSITION_TABLE
_transpositionHits = 0;
_transpositionTable._wrongEntriesFound = 0;
_transpositionTable._tooShallowEntriesFound = 0;
#endif
DateTime startTime = DateTime.Now;
OthelloMoveWithData[] moves = board.GetValidMovesWithData();
MoveWithValue[] movesWithValue = new MoveWithValue[moves.Length];
for (int i = 0; i < moves.Length; i++)
{
movesWithValue[i] = new MoveWithValue();
movesWithValue[i].Move = moves[i];
}
int currentPly;
#if USE_ITERATIVE_DEEPENING
for (currentPly = 0; ; currentPly++)
{
//for (currentPly = 0; currentPly<2; currentPly++) {
#else
for (int currentPly = ply - 1; currentPly < ply; currentPly++)
{
#endif
statusString.Length = 0;
DateTime startIterationTime = DateTime.Now;
statusString.Append("Depth " + (currentPly + 1).ToString() + ": ");
// Should we do a final search
if (board.EmptySquares <= 15 && currentPly > 5)
{
currentPly = board.EmptySquares;
}
int alpha = WORST_MOVE;
int beta = BEST_MOVE;
foreach (MoveWithValue move in movesWithValue)
{
board.PlayMove(move.Move);
statusString.Append(move.Move.ToString());
this.PostStatus(statusString.ToString());
move.Value = (-GetBoardValueRecursive(board, currentPly, 2, -beta, -alpha));
if (move.Value != BEST_MOVE && move.Value != WORST_MOVE)
{
statusString.Append("(" + move.Value.ToString() + ")");
}
statusString.Append(" ");
this.PostStatus(statusString.ToString());
board.UnplayMove(move.Move);
if (move.Value > alpha)
{
alpha = move.Value;
}
if (alpha >= beta)
{
break;
}
}
Array.Sort(movesWithValue);
// If we've already search to the end, we're done
if (currentPly == board.EmptySquares)
{
break;
}
if (movesWithValue[0].Value < -500 || movesWithValue[0].Value > 500)
{
break;
}
TimeSpan t = DateTime.Now - startTime;
if (t.TotalSeconds >= 3)
{
break;
}
}
PlayerResult result = new PlayerResult();
result.Move = movesWithValue[0].Move;
TimeSpan processingTime = DateTime.Now - startTime;
statusString.Append("\r\nEvals: " + _boardEvaluations + " Final evals: " + _finalEvaluations + "\r\n");
#if USE_TRANSPOSITION_TABLE
/*
* statusString.Append("Transp: " + _transpositionHits +
* " wrong hits: " + _transpositionTable._wrongEntriesFound +
* " shallow hits: " + _transpositionTable._tooShallowEntriesFound + "\r\n");
*/
#endif
statusString.Append("Score: " + movesWithValue[0].Value + " (" + processingTime + ")");
result.Status = statusString.ToString();
return(result);
}