/// <summary>
/// Should only be called through the public Search method.
/// </summary>
/// <param name="state">The game state to consider.</param>
/// <param name="isLightPlayer">The player to move.</param>
/// <param name="alpha">The alpha pruning value.</param>
/// <param name="beta">The beta pruning value.</param>
/// <param name="depth">The current search depth.</param>
/// <returns>A MinimaxMove that represents the best move found.</returns>
/// <remarks>
/// The initial alpha value should be Int32.MinValue, the initial beta value
/// should be Int32.MaxValue, and the initial depth value should be 0.
///
/// The search will terminate ASAP if the m_ct cancellation token is signaled.
///
/// This method is thread-safe.
/// </remarks>
private MinimaxMove InternalSearch(MinimaxSpot[,] state, bool isLightPlayer, int alpha, int beta, int depth)
{
// Stop the search if...
if (TerminalTest(state) || depth >= m_maxDepth || m_ct.IsCancellationRequested)
{
m_movesConsidered++;
return(new MinimaxMove(EvaluateHeuristic(state)));
}
// Initialize the best move for this recursive call.
MinimaxMove bestMove = new MinimaxMove(isLightPlayer ? Int32.MinValue : Int32.MaxValue);
// Get the valid moves for this recursive call.
IEnumerable <MinimaxMove> validMoves = GetValidMoves(state, isLightPlayer);
// If there are valid moves, recurse on each.
bool consideredLocalMoves = false;
foreach (MinimaxMove move in validMoves)
{
consideredLocalMoves = true;
MinimaxMove curMove = move;
curMove.Value = InternalSearch(GetInsight(state, curMove, isLightPlayer), !isLightPlayer, alpha, beta, depth + 1).Value;
if (isLightPlayer)
{
if (curMove.Value > bestMove.Value)
{
bestMove = curMove;
}
if (bestMove.Value >= beta)
{
break;
}
alpha = Math.Max(alpha, bestMove.Value.Value);
}
else
{
if (curMove.Value < bestMove.Value)
{
bestMove = curMove;
}
if (bestMove.Value <= alpha)
{
break;
}
beta = Math.Min(beta, bestMove.Value.Value);
}
}
// If there were no valid moves, still calculate the value.
if (!consideredLocalMoves)
{
bestMove.Value = InternalSearch(state, !isLightPlayer, alpha, beta, depth + 1).Value;
}
return(bestMove);
}
protected override MinimaxSpot[,] GetInsight(MinimaxSpot[,] state, MinimaxMove move, bool isLightPlayer)
{
MinimaxSpot[,] insightState = new MinimaxSpot[m_numRows, m_numCols];
for (int i = 0; i < m_numRows; i++)
{
for (int j = 0; j < m_numCols; j++)
{
insightState[i, j] = state[i, j];
}
}
insightState[move.Row, move.Col] = isLightPlayer ? MinimaxSpot.Light : MinimaxSpot.Dark;
return(insightState);
}
/// <summary>
/// Returns the best move resulting from a Minimax, alpha-beta pruning search on the given state.
/// </summary>
/// <param name="state">The state to consider.</param>
/// <param name="isLightPlayer">The player to move.</param>
/// <param name="inParallel">A boolean indicating whether to use the parallel algorithm.</param>
/// <returns>A MinimaxMove that represents the best move found.</returns>
/// <remarks>
/// This method will only return a MinimaxMove(-1...) if there are no valid moves.
/// </remarks>
public MinimaxMove Search(MinimaxSpot[,] state, bool isLightPlayer, bool inParallel)
{
// Initialize a bunch of state.
m_maxDepth = MaxDepth == -1 ? Int32.MaxValue : MaxDepth;
m_degOfParallelism = DegreeOfParallelism;
m_timeLimit = TimeLimit;
m_taskCount = 0;
m_movesConsidered = 0;
var curCts = m_cts = new CancellationTokenSource();
m_ct = m_cts.Token;
MinimaxMove aiMove = new MinimaxMove(-1, -1, null);
// Start the timeout timer. Done using a dedicated thread to minimize delay
// in cancellation due to lack of threads in the pool to run the callback.
var timeoutTask = Task.Factory.StartNew(() =>
{
Thread.Sleep(m_timeLimit);
curCts.Cancel();
}, TaskCreationOptions.LongRunning);
// Do the search
aiMove = inParallel ?
InternalSearchTPL(state, isLightPlayer, Int32.MinValue, Int32.MaxValue, 0, CancellationToken.None) :
InternalSearch(state, isLightPlayer, Int32.MinValue, Int32.MaxValue, 0);
// Make sure that MinimaxMove(-1...) is only returned if there are no valid moves, because
// InternalSearch* may return MinimaxMove(-1...) if none of the valid moves beats Int32.Min/Max.
if (aiMove.Row == -1)
{
foreach (var move in GetValidMoves(state, isLightPlayer))
{
aiMove = move;
aiMove.Value = isLightPlayer ? Int32.MinValue : Int32.MaxValue;
break;
}
}
return(aiMove);
}
/// <summary> /// Returns the game state that results when the given player plays the given move on the given /// state. If the move is invalid, the new state should be the same as the old state. /// Must be thread-safe. /// </summary> /// <param name="state">The state to play a move on.</param> /// <param name="move">The move to play.</param> /// <param name="isLightPlayer">The player to play the move.</param> /// <returns>A MinimaxSpot matrix that represents the insight state.</returns> protected abstract MinimaxSpot[,] GetInsight(MinimaxSpot[,] state, MinimaxMove move, bool isLightPlayer);
/// <summary>
/// Should only be called through the public Search method.
/// </summary>
/// <param name="state">The game state to consider.</param>
/// <param name="isLightPlayer">The player to move.</param>
/// <param name="alpha">The alpha pruning value.</param>
/// <param name="beta">The beta pruning value.</param>
/// <param name="depth">The current search depth.</param>
/// <param name="token">The pruning token.</param>
/// <returns>A MinimaxMove that represents the best move found.</returns>
/// <remarks>
/// The initial alpha value should be Int32.MinValue, the initial beta value
/// should be Int32.MaxValue, the initial depth value should be 0, and the
/// initial token should be a non-settable token.
///
/// The search will terminate ASAP if the m_ct cancellation token is signaled.
///
/// This method is thread-safe.
/// </remarks>
private MinimaxMove InternalSearchTPL(MinimaxSpot[,] state, bool isLightPlayer, int alpha, int beta, int depth, CancellationToken token)
{
// Stop the search if...
if (TerminalTest(state) || depth >= m_maxDepth || m_ct.IsCancellationRequested)
{
m_movesConsidered++; // NOTE: this is racy and may be lower than the actual count, but it only needs to be an appx
return(new MinimaxMove(EvaluateHeuristic(state)));
}
// Initialize the best move for this recursive call.
MinimaxMove bestMove = new MinimaxMove(isLightPlayer ? Int32.MinValue : Int32.MaxValue);
// Get the valid moves for this recursive call.
IEnumerable <MinimaxMove> validMoves = GetValidMoves(state, isLightPlayer);
bool consideredLocalMoves = false;
Queue <Task> workers = new Queue <Task>();
object bigLock = new object();
CancellationTokenSource cts = new CancellationTokenSource();
foreach (MinimaxMove move in validMoves)
{
// SHARED STATE
// The local variables (bestMove, alpha, beta) are protected by a lock.
// The non-local variables (m_taskCount) are modified using Interlocked
consideredLocalMoves = true;
// If the pruning token is signaled, stop this loop.
if (token.IsCancellationRequested)
{
cts.Cancel();
break;
}
MinimaxMove curMove = move;
if (m_taskCount < m_degOfParallelism && depth <= m_maxDepth - 1)
{
Interlocked.Increment(ref m_taskCount);
workers.Enqueue(Task.Factory.StartNew(() =>
{
curMove.Value = InternalSearchTPL(GetInsight(state, curMove, isLightPlayer), !isLightPlayer, alpha, beta, depth + 1, cts.Token).Value;
lock (bigLock)
{
if (isLightPlayer)
{
if (curMove.Value > bestMove.Value)
{
bestMove = curMove;
}
if (bestMove.Value >= beta)
{
cts.Cancel();
}
alpha = Math.Max(alpha, bestMove.Value.Value);
}
else
{
if (curMove.Value < bestMove.Value)
{
bestMove = curMove;
}
if (bestMove.Value <= alpha)
{
cts.Cancel();
}
beta = Math.Min(beta, bestMove.Value.Value);
}
}
Interlocked.Decrement(ref m_taskCount);
}));
}
else
{
bool isPruning = false;
curMove.Value = InternalSearchTPL(GetInsight(state, curMove, isLightPlayer), !isLightPlayer, alpha, beta, depth + 1, cts.Token).Value;
// If there are no tasks, no need to lock.
bool lockTaken = false;
try
{
if (workers.Count > 0)
{
Monitor.Enter(bigLock, ref lockTaken);
}
if (isLightPlayer)
{
if (curMove.Value > bestMove.Value)
{
bestMove = curMove;
}
if (bestMove.Value >= beta)
{
isPruning = true;
}
alpha = Math.Max(alpha, bestMove.Value.Value);
}
else
{
if (curMove.Value < bestMove.Value)
{
bestMove = curMove;
}
if (bestMove.Value <= alpha)
{
isPruning = true;
}
beta = Math.Min(beta, bestMove.Value.Value);
}
}
finally { if (lockTaken)
{
Monitor.Exit(bigLock);
}
}
if (isPruning)
{
cts.Cancel();
break;
}
}
}
Task.WaitAll(workers.ToArray());
// If there were no valid moves, still calculate the value.
if (!consideredLocalMoves)
{
bestMove.Value = InternalSearchTPL(state, !isLightPlayer, alpha, beta, depth + 1, token).Value;
}
return(bestMove);
}
/// <summary>
/// Should only be called through the public Search method.
/// </summary>
/// <param name="state">The game state to consider.</param>
/// <param name="isLightPlayer">The player to move.</param>
/// <param name="alpha">The alpha pruning value.</param>
/// <param name="beta">The beta pruning value.</param>
/// <param name="depth">The current search depth.</param>
/// <returns>A MinimaxMove that represents the best move found.</returns>
/// <remarks>
/// The initial alpha value should be Int32.MinValue, the initial beta value
/// should be Int32.MaxValue, and the initial depth value should be 0.
///
/// The search will terminate ASAP if the m_ct cancellation token is signaled.
///
/// This method is thread-safe.
/// </remarks>
private MinimaxMove InternalSearch(MinimaxSpot[,] state, bool isLightPlayer, int alpha, int beta, int depth)
{
// Stop the search if...
if (TerminalTest(state) || depth >= m_maxDepth || m_ct.IsCancellationRequested)
{
m_movesConsidered++;
return new MinimaxMove(EvaluateHeuristic(state));
}
// Initialize the best move for this recursive call.
MinimaxMove bestMove = new MinimaxMove(isLightPlayer ? Int32.MinValue : Int32.MaxValue);
// Get the valid moves for this recursive call.
IEnumerable<MinimaxMove> validMoves = GetValidMoves(state, isLightPlayer);
// If there are valid moves, recurse on each.
bool consideredLocalMoves = false;
foreach (MinimaxMove move in validMoves)
{
consideredLocalMoves = true;
MinimaxMove curMove = move;
curMove.Value = InternalSearch(GetInsight(state, curMove, isLightPlayer), !isLightPlayer, alpha, beta, depth + 1).Value;
if (isLightPlayer)
{
if (curMove.Value > bestMove.Value) bestMove = curMove;
if (bestMove.Value >= beta) break;
alpha = Math.Max(alpha, bestMove.Value.Value);
}
else
{
if (curMove.Value < bestMove.Value) bestMove = curMove;
if (bestMove.Value <= alpha) break;
beta = Math.Min(beta, bestMove.Value.Value);
}
}
// If there were no valid moves, still calculate the value.
if (!consideredLocalMoves)
{
bestMove.Value = InternalSearch(state, !isLightPlayer, alpha, beta, depth + 1).Value;
}
return bestMove;
}
/// <summary> /// Returns the game state that results when the given player plays the given move on the given /// state. If the move is invalid, the new state should be the same as the old state. /// Must be thread-safe. /// </summary> /// <param name="state">The state to play a move on.</param> /// <param name="move">The move to play.</param> /// <param name="isLightPlayer">The player to play the move.</param> /// <returns>A MinimaxSpot matrix that represents the insight state.</returns> protected abstract MinimaxSpot[,] GetInsight(MinimaxSpot[,] state, MinimaxMove move, bool isLightPlayer);
/// <summary>
/// Returns the best move resulting from a Minimax, alpha-beta pruning search on the given state.
/// </summary>
/// <param name="state">The state to consider.</param>
/// <param name="isLightPlayer">The player to move.</param>
/// <param name="inParallel">A boolean indicating whether to use the parallel algorithm.</param>
/// <returns>A MinimaxMove that represents the best move found.</returns>
/// <remarks>
/// This method will only return a MinimaxMove(-1...) if there are no valid moves.
/// </remarks>
public MinimaxMove Search(MinimaxSpot[,] state, bool isLightPlayer, bool inParallel)
{
// Initialize a bunch of state.
m_maxDepth = MaxDepth == -1 ? Int32.MaxValue : MaxDepth;
m_degOfParallelism = DegreeOfParallelism;
m_timeLimit = TimeLimit;
m_taskCount = 0;
m_movesConsidered = 0;
var curCts = m_cts = new CancellationTokenSource();
m_ct = m_cts.Token;
MinimaxMove aiMove = new MinimaxMove(-1, -1, null);
// Start the timeout timer. Done using a dedicated thread to minimize delay
// in cancellation due to lack of threads in the pool to run the callback.
var timeoutTask = Task.Factory.StartNew(() =>
{
Thread.Sleep(m_timeLimit);
curCts.Cancel();
}, TaskCreationOptions.LongRunning);
// Do the search
aiMove = inParallel ?
InternalSearchTPL(state, isLightPlayer, Int32.MinValue, Int32.MaxValue, 0, CancellationToken.None) :
InternalSearch(state, isLightPlayer, Int32.MinValue, Int32.MaxValue, 0);
// Make sure that MinimaxMove(-1...) is only returned if there are no valid moves, because
// InternalSearch* may return MinimaxMove(-1...) if none of the valid moves beats Int32.Min/Max.
if (aiMove.Row == -1)
{
foreach (var move in GetValidMoves(state, isLightPlayer))
{
aiMove = move;
aiMove.Value = isLightPlayer ? Int32.MinValue : Int32.MaxValue;
break;
}
}
return aiMove;
}
/// <summary>
/// Should only be called through the public Search method.
/// </summary>
/// <param name="state">The game state to consider.</param>
/// <param name="isLightPlayer">The player to move.</param>
/// <param name="alpha">The alpha pruning value.</param>
/// <param name="beta">The beta pruning value.</param>
/// <param name="depth">The current search depth.</param>
/// <param name="token">The pruning token.</param>
/// <returns>A MinimaxMove that represents the best move found.</returns>
/// <remarks>
/// The initial alpha value should be Int32.MinValue, the initial beta value
/// should be Int32.MaxValue, the initial depth value should be 0, and the
/// initial token should be a non-settable token.
///
/// The search will terminate ASAP if the m_ct cancellation token is signaled.
///
/// This method is thread-safe.
/// </remarks>
private MinimaxMove InternalSearchTPL(MinimaxSpot[,] state, bool isLightPlayer, int alpha, int beta, int depth, CancellationToken token)
{
// Stop the search if...
if (TerminalTest(state) || depth >= m_maxDepth || m_ct.IsCancellationRequested)
{
m_movesConsidered++; // NOTE: this is racy and may be lower than the actual count, but it only needs to be an appx
return new MinimaxMove(EvaluateHeuristic(state));
}
// Initialize the best move for this recursive call.
MinimaxMove bestMove = new MinimaxMove(isLightPlayer ? Int32.MinValue : Int32.MaxValue);
// Get the valid moves for this recursive call.
IEnumerable<MinimaxMove> validMoves = GetValidMoves(state, isLightPlayer);
bool consideredLocalMoves = false;
Queue<Task> workers = new Queue<Task>();
object bigLock = new object();
CancellationTokenSource cts = new CancellationTokenSource();
foreach (MinimaxMove move in validMoves)
{
// SHARED STATE
// The local variables (bestMove, alpha, beta) are protected by a lock.
// The non-local variables (m_taskCount) are modified using Interlocked
consideredLocalMoves = true;
// If the pruning token is signaled, stop this loop.
if (token.IsCancellationRequested)
{
cts.Cancel();
break;
}
MinimaxMove curMove = move;
if (m_taskCount < m_degOfParallelism && depth <= m_maxDepth - 1)
{
Interlocked.Increment(ref m_taskCount);
workers.Enqueue(Task.Factory.StartNew(() =>
{
curMove.Value = InternalSearchTPL(GetInsight(state, curMove, isLightPlayer), !isLightPlayer, alpha, beta, depth + 1, cts.Token).Value;
lock (bigLock)
{
if (isLightPlayer)
{
if (curMove.Value > bestMove.Value) bestMove = curMove;
if (bestMove.Value >= beta) cts.Cancel();
alpha = Math.Max(alpha, bestMove.Value.Value);
}
else
{
if (curMove.Value < bestMove.Value) bestMove = curMove;
if (bestMove.Value <= alpha) cts.Cancel();
beta = Math.Min(beta, bestMove.Value.Value);
}
}
Interlocked.Decrement(ref m_taskCount);
}));
}
else
{
bool isPruning = false;
curMove.Value = InternalSearchTPL(GetInsight(state, curMove, isLightPlayer), !isLightPlayer, alpha, beta, depth + 1, cts.Token).Value;
// If there are no tasks, no need to lock.
bool lockTaken = false;
try
{
if (workers.Count > 0) Monitor.Enter(bigLock, ref lockTaken);
if (isLightPlayer)
{
if (curMove.Value > bestMove.Value) bestMove = curMove;
if (bestMove.Value >= beta) isPruning = true;
alpha = Math.Max(alpha, bestMove.Value.Value);
}
else
{
if (curMove.Value < bestMove.Value) bestMove = curMove;
if (bestMove.Value <= alpha) isPruning = true;
beta = Math.Min(beta, bestMove.Value.Value);
}
}
finally { if (lockTaken) Monitor.Exit(bigLock); }
if (isPruning)
{
cts.Cancel();
break;
}
}
}
Task.WaitAll(workers.ToArray());
// If there were no valid moves, still calculate the value.
if (!consideredLocalMoves)
{
bestMove.Value = InternalSearchTPL(state, !isLightPlayer, alpha, beta, depth + 1, token).Value;
}
return bestMove;
}
private void GoAI()
{
if (m_isGameOver)
{
return;
}
m_isAIMoving = true;
m_progBarAnim = new DoubleAnimation(0.0, 100.0, m_progBarDuration);
if (m_isAIParallel)
{
ui_parProgBar.Visibility = Visibility.Visible;
ui_parProgBar.BeginAnimation(ProgressBar.ValueProperty, m_progBarAnim, HandoffBehavior.SnapshotAndReplace);
}
else
{
ui_seqProgBar.Visibility = Visibility.Visible;
ui_seqProgBar.BeginAnimation(ProgressBar.ValueProperty, m_progBarAnim, HandoffBehavior.SnapshotAndReplace);
}
m_aiUICts = new CancellationTokenSource();
m_aiUITask = Task.Factory.StartNew(() =>
{
return(m_game.GetAIMove(m_isAIParallel));
}, m_aiUICts.Token, TaskCreationOptions.None, TaskScheduler.Default)
.ContinueWith(completedTask =>
{
MinimaxMove aiMove = completedTask.Result;
if (aiMove.Row != -1)
{
m_game.MakeMove(aiMove.Row, aiMove.Col);
}
else
{
m_game.PassMove();
}
string s;
if (m_isAIParallel)
{
s = String.Format("{0:N}", m_game.MovesConsidered);
s = s.Substring(0, s.Length - 3);
ui_parLabel.Content = s;
ui_parProgBar.Visibility = Visibility.Hidden;
}
else
{
s = String.Format("{0:N}", m_game.MovesConsidered);
s = s.Substring(0, s.Length - 3);
ui_seqLabel.Content = s;
ui_seqProgBar.Visibility = Visibility.Hidden;
}
UpdateBoard();
m_isAIMoving = false;
if (m_isAuto)
{
m_isAIParallel = !m_isAIParallel;
GoAI();
}
}, m_aiUICts.Token, TaskContinuationOptions.None, m_UIScheduler);
}
