/* This is the minimax function with alpha beta pruning
*
* Inputs: board, the current state; depth, the desired search depth;
* a, the alpha value; b, the beta value; finalDepth, the total search depth
* Output: Tuple<int,int> Result: Item1 = The heuristic of the move. Item2 = the move number
*/
private Tuple <int, int> alphaBeta(Board board, int depth, int a, int b, int finalDepth)
{
int v = 0;
int v2 = 0;
int move = -1;
if (board.gameOver() || depth == 0)
{
return(new Tuple <int, int>(0, evaluate(board, finalDepth)));
}
if (board.whoseMove() == Position.Top) // Max player's turn
{
v = -99999;
for (int i = 12; i >= 7; i--) // Try each of the possible moves
{
if (board.legalMove(i) && (move == -1 || timer.ElapsedMilliseconds < getTimePerMove() - 1))
{
Board board1 = new Board(board);
board1.makeMove(i, false);
v2 = alphaBeta(board1, depth - 1, a, b, finalDepth).Item2; // Find value of that move
if (v2 > v) // pick the best move
{
v = v2;
move = i;
}
a = Math.Max(a, v);
if (b <= a)
{
break;
}
}
}
return(new Tuple <int, int>(move, v)); // Return the result
}
else // Minimizing player's turn
{
v = 99999;
for (int i = 5; i >= 0; i--) // Try each of the possible moves
{
if (board.legalMove(i) && (move == -1 || timer.ElapsedMilliseconds < getTimePerMove() - 1))
{
Board board1 = new Board(board);
board1.makeMove(i, false);
v2 = alphaBeta(board1, depth - 1, a, b, finalDepth).Item2; // Find value of that move
if (v2 < v) // Pick the best move
{
v = v2;
move = i;
}
b = Math.Min(b, v);
if (b <= a)
{
break;
}
}
}
return(new Tuple <int, int>(move, v)); // Return the result
}
}
/*
* minimax function
* based on the psuedocode from Prof Plantiga's lecture slides
*/
private Result minimax(Board b, int depth, int alpha, int beta)
{
int bestNum = 0;
int currentBestMove = 0;
if (b.gameOver() || depth == 0) // game is over or depth is 0
{
return(new Result(0, evaluate(b)));
}
if (b.whoseMove() == Position.Top) // searching moves for when top player
{
bestNum = Int32.MinValue;
for (int move = 7; move <= 12; move++)
{
if (b.legalMove(move))
{
Board b1 = new Board(b);
b1.makeMove(move, false);
Result num = minimax(b1, depth - 1, alpha, beta);
if (num.getBestScore() > bestNum)
{
bestNum = num.getBestScore();
currentBestMove = move;
}
if (bestNum > alpha)
{
alpha = bestNum;
}
}
}
return(new Result(currentBestMove, bestNum));
}
else // search moves for when bottom player
{
bestNum = int.MaxValue;
for (int move = 0; move <= 5; move++)
{
if (b.legalMove(move))
{
Board b1 = new Board(b);
b1.makeMove(move, false);
Result num = minimax(b1, (depth - 1), alpha, beta);
if (num.getBestScore() < bestNum)
{
bestNum = num.getBestScore();
currentBestMove = move;
}
if (bestNum < beta)
{
beta = bestNum;
}
}
}
return(new Result(currentBestMove, bestNum));
}
}
private int[] minmaxVal(Board b, int d, float alpha, float beta, ref Stopwatch timer)
{
if (d == 0 || b.gameOver())
{
return(new int[] { 0, evaluate(b) });
}
int[] bestMove = { 0, int.MinValue };
if (b.whoseMove() == us)
{
int bestVal = int.MinValue;
for (int move = 0; move <= 13; move++)
{
if (b.legalMove(move) && timer.ElapsedMilliseconds < (max_time - 200))
{
Board b1 = new Board(b);
b1.makeMove(move, false);
int[] val = minmaxVal(b1, d - 1, alpha, beta, ref timer);
if (val[1] > bestVal)
{
bestVal = val[1];
bestMove[0] = move;
bestMove[1] = bestVal;
}
alpha = Math.Max(alpha, bestMove[1]);
if (beta <= alpha)
{
break;
}
}
}
}
else
{
int bestVal = int.MaxValue;
bestMove = new int[] { 0, bestVal };
for (int move = 0; move <= 13; move++)
{
if (b.legalMove(move) && timer.ElapsedMilliseconds < (max_time - 200))
{
Board b1 = new Board(b);
b1.makeMove(move, false);
int[] val = minmaxVal(b1, d - 1, alpha, beta, ref timer);
if (val[1] < bestVal)
{
bestVal = val[1];
bestMove[0] = move;
bestMove[1] = bestVal;
}
beta = Math.Min(beta, bestMove[1]);
if (beta <= alpha)
{
break;
}
}
}
}
return(bestMove);
}
/* Minimax search
* top player is max and bottom is min
* returns a resulting move from recursive calculations
*/
private Result minimax(Board board, int depth, int alpha, int beta)
{
if (board.gameOver() || depth == 0)
{
return(new Result(0, evaluate(board)));
}
int bestVal = int.MinValue;
int bestMove = 0;
if (board.whoseMove() == Position.Top)
{
for (int move = 7; move < 13 && alpha < beta; move++)
{
if (board.legalMove(move))
{
Board b1 = new Board(board);
b1.makeMove(move, false);
Result val = minimax(b1, depth - 1, alpha, beta);
if (val.getBestScore() > bestVal)
{
bestVal = val.getBestScore();
bestMove = move;
}
if (bestVal > alpha)
{
alpha = bestVal;
}
}
}
}
else
{
bestVal = Int32.MaxValue;
for (int move = 0; move < 6 && alpha < beta; move++)
{
if (board.legalMove(move))
{
Board b1 = new Board(board);
b1.makeMove(move, false);
Result val = minimax(b1, depth - 1, alpha, beta);
if (val.getBestScore() < bestVal)
{
bestVal = val.getBestScore();
bestMove = move;
}
if (bestVal < beta)
{
beta = bestVal;
}
}
}
}
return(new Result(bestMove, bestVal));
}
/* minimax()
* @param: b, a Board type && d, and int type
* returns new Result w/ bestMove && bestValue
* this code follows the pseudocode given in class
*/
private Result minimaxVal(Board b, int d, int alpha, int beta) //d is depth
{
int bestValue = 0;
int bestMove = 0;
if (b.gameOver() || d == 0) //if the game is over or depth is 0
{
return(new Result(0, evaluate(b)));
}
if (b.whoseMove() == Position.Top)
{ //if TOP is max
bestValue = Int32.MinValue;
for (int move = 7; move <= 12 && alpha < beta; move++)
{
if (b.legalMove(move))
{
Board b1 = new Board(b); //duplicate board
b1.makeMove(move, false);
Result val = minimaxVal(b1, d - 1, alpha, beta);
if (val.GetScore() > bestValue)
{
bestValue = val.GetScore(); bestMove = move;
}
if (bestValue > alpha)
{
alpha = bestValue;
}
}
}
return(new Result(bestMove, bestValue));
}
else
{
bestValue = int.MaxValue;
for (int move = 0; move <= 5 && alpha < beta; move++) //bottom row
{
if (b.legalMove(move))
{
Board b1 = new Board(b);
b1.makeMove(move, false);
Result val = minimaxVal(b1, d - 1, alpha, beta);
if (val.GetScore() < bestValue)
{
bestValue = val.GetScore(); bestMove = move;
}
if (bestValue < beta)
{
beta = bestValue;
}
}
}
}
return(new Result(bestMove, bestValue));
}
/* miniMaxVal implements the minimax search of a board for a given depth
* @param: board, the Board whose child boards will be evaluated
* @param: depth, how many generations will be analyzed
* @return: a Result that is the optimal move and its value
*/
private Result miniMaxVal(Board board, int depth)
{
int bestMove = -1; // dummy value
int bestVal = 0; // dummy value
if (board.gameOver() || (depth == 0))
{
return(new Result(0, evaluate(board)));
}
if (board.whoseMove() == Position.Top) // max
{
bestVal = -9999999; // impossible to get less than this
for (int move = 7; move <= 12; move++)
{
if (board.legalMove(move) && !timeUp) // stop if the timer has finished
{
Board boardCopy = new Board(board);
boardCopy.makeMove(move, false);
Result moveResult = miniMaxVal(boardCopy, depth - 1);
if (moveResult.value > bestVal)
{
bestVal = moveResult.value;
bestMove = move;
}
}
}
}
else // BOTTOM'S MOVE (min)
{
bestVal = 9999999; // impossible to get more than this
for (int move = 0; move <= 5; move++)
{
if (board.legalMove(move) && !timeUp) // stop if the timer has finished
{
Board boardCopy = new Board(board);
boardCopy.makeMove(move, false);
Result moveResult = miniMaxVal(boardCopy, depth - 1);
if (moveResult.value < bestVal)
{
bestVal = moveResult.value;
bestMove = move;
}
}
}
}
return(new Result(bestMove, bestVal));
}
public override int chooseMove(Board b)
{
int move = -1;
string moveString;
while (!b.legalMove(move))
{
Console.Write("Your move: ");
moveString = Console.ReadLine();
if (!int.TryParse(moveString, out move) || !b.legalMove(move))
{
Console.WriteLine("Illegal move. Try again.");
}
}
return(move);
}
/// <summary>
/// MiniMax algorithm for mankalah. Uses the moveResult class, probably doesn't need to and
/// could use it much more efficiently, but for times sake...
/// This method finds returns the best move based on its rating.
/// </summary>
/// <param name="b"></param> which mankalah board
/// <param name="d"></param> depth of which algotithm will recurse
/// <returns></returns>
private moveResult miniMax(Board b, int d)
{
moveResult moveVal = new moveResult(0, 0); //uses result class at bottom
moveResult bestMoveVal = new moveResult(0, 0); // ^^
if (b.gameOver() || d == 0)
{
return(new moveResult(0, evaluate(b))); //evaluate function is simple. Bad thing?
}
if (b.whoseMove() == Position.Bottom)
{
bestMoveVal.val = 999;
for (int move = 0; move <= 5; move++) //for all possible moves,
{
if (b.legalMove(move) && myWatch.ElapsedMilliseconds < timePerMove) /*and time not expired*/
{
Board b1 = new Board(b); //dup board b
b1.makeMove(move, false); //make move
moveVal = miniMax(b1, d - 1); //recurse and return value
if (moveVal.val < bestMoveVal.val)
{
bestMoveVal = moveVal; bestMoveVal.move = move;
} //overwrite if better move
}
}
return(bestMoveVal); //return best move found.
}
else //similar comments as above...
{
bestMoveVal.val = -999;
for (int move = 7; move <= 12; move++)
{
if (b.legalMove(move) && myWatch.ElapsedMilliseconds < timePerMove) /*and time not expired*/
{
Board b1 = new Board(b); //dup board b
b1.makeMove(move, false);
moveVal = miniMax(b1, d - 1);
if (moveVal.val > bestMoveVal.val)
{
bestMoveVal = moveVal; bestMoveVal.move = move;
}
}
}
return(bestMoveVal);
}
}
public override int chooseMove(Board b)
{
int tL = 4;
Timer timer = new Timer(tL);
timeOut = false;
timer.Elapsed += timeOutTrigger;
timer.Enabled = true;
timer.AutoReset = false;
timer.Start();
List <int> choices = new List <int>();
int choice = 0;
int startDepth = 11;
//Pass in timer to minimax?
//If the elapsed time matches or exceeds the time limit, break the loop
while (true)
{
if (timeOut || b.gameOver())
{
break;
}
Console.WriteLine("Depth: " + startDepth);
if (startDepth > 20)
{
Console.WriteLine("We might have a problem");
}
//If the value of choice is not 0, add it to the list of choices.
moveResult choiceResult = new moveResult(0, 0);
if (!timeOut)
{
choiceResult = miniMax(b, startDepth, tL, 1, timer);
}
if (choiceResult.getScore() != 0 && b.legalMove(choiceResult.getMove()))
{
//TODO: Adding stuff to a list seems to not work
choices.Add(choiceResult.getMove());
}
//choice = miniMax(b, startDepth, tL).getScore();
//TODO: Modify timer and Stop, store and print time elapsed
//update depth.
startDepth += 1;
if (timeOut == true)
{
timer.Stop();
}
}
//Close the timer and return the move from the last item in the list of choices
timer.Close();
return(choices.Last());
}
public override int chooseMove(Board b)
{
int move;
Random rnd = new Random();
while (true)
{
move = rnd.Next(13);
if (b.legalMove(move))
{
return(move);
}
}
}
//Minimax function. Note that the Max is for the bottom play, It just made more sense to me that way. returns best score and best move.
private int[] prunedminimax(Board b, int depth, Stopwatch timer, int lastbestscore, Position lastplayer, int playsinarow)
{
int[] value = new int[2];
int bestscore;
if (b.whoseMove() == Position.Top) //set the infinity max or infinity min depending on whose turn it is.
{
bestscore = 1111111;
}
else
{
bestscore = -1111111;
}
int bestmove = -1; //returns this number if DFS doesnt finish
int[] tempvalue = new int[2]; //temporary value that will be used to find the best score and value
if ((depth > 0 && !b.gameOver())) //as long as game isnt over, or you reached the depth
{
bool firstturn = true; //used to keep track of the first turn
for (int i = 0; i < 6; i++)
{
if (b.whoseMove() == Position.Top)
{
if (b.legalMove(i + 7))
{
Board currentBoard = new Board(b);
currentBoard.makeMove(i + 7, false);
if (lastplayer == Position.Top)//this is used to keep track of who has had the most turns
{
tempvalue = prunedminimax(currentBoard, depth - 1, timer, bestscore, Position.Top, playsinarow - 1);
}
else
{
tempvalue = prunedminimax(currentBoard, depth - 1, timer, bestscore, Position.Top, playsinarow);
}
if (firstturn)
{
bestscore = tempvalue[0];
bestmove = i + 7;
firstturn = false;//no longer first turn so set to false
}
//for non-first turns, check to see if tempvalue is lower then best score.
else if (tempvalue[0] < bestscore)
{
bestscore = tempvalue[0];
bestmove = i + 7;
}
if ((lastplayer == Position.Bottom) && (bestscore < lastbestscore))
{
break; //prunes the branches if necesary.
}
}
}
else
{
if (b.legalMove(i))
{
Board currentBoard = new Board(b);
currentBoard.makeMove(i, false);
if (lastplayer == Position.Bottom)
{
tempvalue = prunedminimax(currentBoard, depth - 1, timer, bestscore, Position.Bottom, playsinarow + 1);
}
else
{
tempvalue = prunedminimax(currentBoard, depth - 1, timer, bestscore, Position.Bottom, playsinarow);
}
if (firstturn)
{
bestscore = tempvalue[0];
bestmove = i;
firstturn = false;
}
else if (tempvalue[0] > bestscore)
{
bestscore = tempvalue[0];
bestmove = i;
}
if ((lastplayer == Position.Top) && (bestscore > lastbestscore))
{
break;
}
}
}
if (!(timer.ElapsedMilliseconds < getTimePerMove() - 10))//if there are only 10 ms till the turn is up, return -1 for the best move
{
value[1] = -1;
return(value);
}
}
}
else //reaches this if it is a node.
{
bestscore = evaluate(b, playsinarow);
}
value[0] = bestscore;
value[1] = bestmove;
return(value);
}
public Result miniMax(Board b, int d, int alpha, int beta)
{
if (cancellationToken.IsCancellationRequested)
{
throw new OperationCanceledException();
}
int bestMove = first;
int bestVal = 0;
Result res;
Position opp;
if (b.gameOver() || d == 0)
{
return(new Result(0, evaluate(b)));
}
if (b.whoseMove() == p)
{ //top is max
bestVal = -int.MaxValue;
for (int move = first; move <= last; move++)
{
if (b.legalMove(move))
{
Board b1 = new Board(b); //duplicate board
b1.makeMove(move, false); //make the move
res = miniMax(b1, d - 1, alpha, beta); //find its value
alpha = Math.Max(alpha, res.val);
if (res.val > bestVal)
{
bestVal = res.val;
bestMove = move;
}
if (alpha >= beta)
{
break;
}
}
}
}
else
{ // similarly for bottom’s move
bestVal = int.MaxValue;
for (int move = p2first; move <= p2last; move++)
{
if (b.legalMove(move))
{
Board b1 = new Board(b); //duplicate board
b1.makeMove(move, false); //make the move
res = miniMax(b1, d - 1, alpha, beta); //find its value
beta = Math.Min(beta, res.val);
if (res.val < bestVal) //remember if best
{
bestVal = res.val;
bestMove = move;
}
if (alpha >= beta)
{
break;
}
}
}
}
return(new Result(bestMove, bestVal));
}
public int[] minmaxVal(Board b, int depth, float alpha, float beta, ref Stopwatch sw)
{
if (depth == 0)
{
return new int[] { 0, evaluate(b) }
}
;
if (b.gameOver())
{
maxDepth = depth;
return(new int[] { 0, endGameEval(b) });
}
int[] bestMove = { 0, int.MinValue };
//our turn -> maximize
if (b.whoseMove() == us)
{
bestMove = new int[] { 0, int.MinValue };
for (int i = 0; i < 13; i++)
{
if (b.legalMove(i))
{
if (sw.ElapsedMilliseconds >= timeLimit - 100)
{
//return new int[] { 0, int.MinValue };
return new int[] { i, evaluate(b) }
}
;
Board modified = SimulateBoard(b, i);
int[] newMove = minmaxVal(modified, depth - 1, alpha, beta, ref sw);
if (newMove[1] > bestMove[1])
{
bestMove[0] = i;
bestMove[1] = newMove[1];
//Console.WriteLine($"Changed bestMove in max to move {i} with value {bestMove[1]}");
}
alpha = Math.Max(alpha, bestMove[1]);
if (beta <= alpha)
{
break;
}
}
}
}
//Their turn -> minimize
else
{
bestMove = new int[] { 0, int.MaxValue };
for (int i = 0; i < 13; i++)
{
if (b.legalMove(i))
{
if (sw.ElapsedMilliseconds >= timeLimit - 100)
{
//return new int[] { 0, int.MaxValue };
return new int[] { i, evaluate(b) }
}
;
Board modified = SimulateBoard(b, i);
int[] newMove = minmaxVal(modified, depth - 1, alpha, beta, ref sw);
if (newMove[1] < bestMove[1])
{
bestMove[0] = i;
bestMove[1] = newMove[1];
//Console.WriteLine($"Changed bestMove in min to move {i} with value {bestMove[1]}");
}
beta = Math.Min(beta, bestMove[1]);
if (beta <= alpha)
{
break;
}
}
}
}
if (maxDepth != 50)
{
maxDepth = depth;
}
return(bestMove);
}
public int[] minmaxVal(Board b, int d, float alpha, float beta, ref Stopwatch sw) //d is depth
{
if (depth == 0 || b.gameOver())
{
return new int[] { 0, evaluate(b) }
}
;
int[] bestMove = { 0, int.MinValue };
//our turn -> maximize
if (b.whoseMove() == us)
{
bestMove = new int[] { 0, int.MinValue };
for (int i = 0; i < 13; i++)
{
if (b.legalMove(i))
{
if (sw.ElapsedMilliseconds >= timeLimit - 500)
{
return new int[] { 0, int.MinValue }
}
;
Board modified = SimulateBoard(b, i);
int[] newMove = minmaxVal(modified, depth - 1, alpha, beta, ref sw);
if (newMove[1] > bestMove[1])
{
bestMove[0] = i;
bestMove[1] = newMove[1];
}
alpha = Math.Max(alpha, bestMove[1]);
if (beta <= alpha)
{
break;
}
}
}
}
//Their turn -> minimize
else
{
bestMove = new int[] { 0, int.MaxValue };
for (int i = 0; i < 13; i++)
{
if (!b.legalMove(i))
{
if (sw.ElapsedMilliseconds >= timeLimit - 500)
{
return new int[] { 0, int.MaxValue }
}
;
Board modified = SimulateBoard(b, i);
int[] newMove = minmaxVal(modified, depth - 1, alpha, beta, ref sw);
if (newMove[1] > bestMove[1])
{
bestMove[0] = i;
bestMove[1] = newMove;
}
beta = Math.Min(beta, bestMove[1]);
if (beta <= alpha)
{
break;
}
}
}
}
return(bestMove);
}
}
// b = current board state, d = depth, w = clock, alpha and beta to keep track of max/min values for pruning
private Result minimax(Board b, int d, Stopwatch w, int alpha, int beta)
{
// throw exception if time limit has reached
if (w.ElapsedMilliseconds > getTimePerMove())
{
throw new MoveTimedOutException();
}
// initialize variables
int bestMove = 0;
int bestVal;
bool gameCompleted = false;
if (b.gameOver() || d == 0)
{
return(new Result(0, evaluate(b), b.gameOver()));
}
// if it's my move, maximize
if (b.whoseMove() == mypos) // TOP is MAX
{
bestVal = Int32.MinValue; // set bestVal to lowest possible number to update later on
for (int move = myfirst; move <= mylast; move++) // loop through all possible moves for this player
{
if (b.legalMove(move)) // if it's a legal move, make that move, look at board and see if it is best move
{
Board b1 = new Board(b); // duplicate board
b1.makeMove(move, false); // make the move
Result val = minimax(b1, d - 1, w, alpha, beta); // find its value
if (val.getScore() > bestVal) // remember if best maximum
{
bestVal = val.getScore(); // update best move, value, and game state after this move
bestMove = move;
gameCompleted = val.isEndGame();
}
// update alpha
if (bestVal > alpha)
{
alpha = bestVal;
}
}
}
}
// else minimize
else
{
bestVal = Int32.MaxValue; // set bestVal to highest possible number to update later on
for (int move = myfirstOP; move <= mylastOP; move++) // loop through all possible moves for this player
{
if (b.legalMove(move)) // if it's a legal move, make that move, look at board and see if it is best move
{
Board b1 = new Board(b); // duplicate board
b1.makeMove(move, false); // make the move
Result val = minimax(b1, d - 1, w, alpha, beta); // find its value
if (val.getScore() < bestVal) // remember if best minimum
{
bestVal = val.getScore(); // update best move, value, and game state after this move
bestMove = move;
gameCompleted = val.isEndGame();
}
// update beta
if (bestVal < beta)
{
beta = bestVal;
}
}
}
}
// return the Result set with best move, score, and game status
return(new Result(bestMove, bestVal, gameCompleted));
}
// The function minimax() calculates the best possible move that Chappie can make by
// recursing as far as it can within the time limit and keeping track of what the best move and
// score are as it recurses. It is also implemented with AB pruning, meaning that if it
// starts to go down a path where the outcome will inevitable be worse that our best values,
// it prunes off that path, therefore saving time to go down a better path.
private MoveResult minimax(Board b, int d, Stopwatch w, int alpha, int beta)
{
// check to see if the time limit is up
if (w.ElapsedMilliseconds > getTimePerMove())
{
throw new MoveTimedOutException();
}
// base case
if (b.gameOver() || d == 0)
{
return(new MoveResult(0, evaluate(b), b.gameOver()));
}
// initialization of trackers
int bestMove = 0;
int bestVal;
bool gameCompleted = false;
// check all the the moves that top could make, and act as if it is the MAX in minimax
if (b.whoseMove() == Position.Top) // TOP is MAX
{
// smallest possible value so that it can only get better
bestVal = Int32.MinValue;
for (int move = 7; move <= 12 && alpha < beta; move++)
{
if (b.legalMove(move))
{
Board b1 = new Board(b); // duplicate board
b1.makeMove(move, false); // make the move
MoveResult val = minimax(b1, d - 1, w, alpha, beta); // find its value
if (val.getScore() > bestVal) // remember if best
{
bestVal = val.getScore();
bestMove = move;
// track the current condition of the game
gameCompleted = val.isEndGame();
}
// prune
if (bestVal > alpha)
{
alpha = bestVal;
}
}
}
}
// check all the the moves that bottom could make, and act as if it is the MIN in minimax
else // BOTTOM is MIN
{
// lergest possible value so that it can only get better
bestVal = Int32.MaxValue;
for (int move = 0; move <= 5 && alpha < beta; move++)
{
if (b.legalMove(move))
{
Board b1 = new Board(b); // duplicate board
b1.makeMove(move, false); // make the move
MoveResult val = minimax(b1, d - 1, w, alpha, beta); // find its value
if (val.getScore() < bestVal) // remember if best
{
bestVal = val.getScore();
bestMove = move;
// track the current condition of the game
gameCompleted = val.isEndGame();
}
// prune
if (bestVal < beta)
{
beta = bestVal;
}
}
}
}
return(new MoveResult(bestMove, bestVal, gameCompleted));
}
/* minimaxVal with Alpha-Beta Pruning
* returns evaluation if it reaches maxDepth, else calculates min or max if it is opponent's turn or my turn respectively
*
*/
public DataWrapper minimaxVal(Board b, int d, int alpha, int beta)
{
//when time runs out, this evaluates to true
//when the cancelled execption is thrown, the last best move will be returned in the chooseMove() try->catch statement
if (cancellationToken.IsCancellationRequested)
{
throw new OperationCanceledException();
}
//return if reached gameover or max depth
if (b.gameOver() || d == 0)
{
return(new DataWrapper(0, evaluate(b), 0, 0));
}
DataWrapper data;
//look through right positions for moves
int start = 0;
int end = 5;
if (b.whoseMove() == Position.Top)
{
start = 7;
end = 12;
}
//initialize variables
int bestMove = -1;
int secondBestMove = -1;
int bestValue = int.MinValue;
int secondBestValue = int.MinValue;
//loop through all possible moves
for (int move = start; move <= end; move++)
{
//if it is a legal move, check the value of it
if (b.legalMove(move))
{
//create copy of board, make move, and evaluate it by recursing
Board newBoard = new Board(b);
newBoard.makeMove(move, false);
data = minimaxVal(newBoard, d - 1, alpha, beta);
//if value, move pair is best or worst, set bestValue and bestMove to it
//also set second best value, move pair to previous value
if (isBetterMove(b.whoseMove(), bestValue, data.getValue(), d))
{
secondBestValue = bestValue;
bestValue = data.getValue();
secondBestMove = bestMove;
bestMove = move;
//alpha beta pruning
if (b.whoseMove() == this.position)
{
alpha = Math.Max(alpha, bestValue);
}
else
{
beta = Math.Min(beta, bestValue);
}
}
//if alpha is greater than or equal to beta, we can skip other moves (pruning part of alpha beta pruning)
if (alpha >= beta)
{
break;
}
}
}
//return move pairs
return(new DataWrapper(bestMove, bestValue, secondBestMove, secondBestValue));
}
private Result minimaxVal(Board b, int d, Stopwatch w, int alpha, int beta)
{
if (w.ElapsedMilliseconds > getTimePerMove())
{
throw new MoveTimedOutException();
}
int bestMove = 0;
int bestVal;
bool gameCompleted = false;
if (b.gameOver() || d == 0)
{
return(new Result(0, evaluate(b), b.gameOver()));
}
if (b.whoseMove() == Position.Top)
{
bestVal = Int32.MinValue;
for (int move = 7; move <= 12; move++)
{
if (b.legalMove(move))
{
Board b1 = new Board(b);
b1.makeMove(move, false);
Result val = minimaxVal(b1, d - 1, w, alpha, beta);
if (val.getScore() > bestVal)
{
bestVal = val.getScore();
bestMove = move;
gameCompleted = val.isEndGame();
}
if (bestVal > alpha)
{
alpha = bestVal;
}
}
}
}
else
{
bestVal = Int32.MaxValue;
for (int move = 0; move <= 5; move++)
{
if (b.legalMove(move))
{
Board b1 = new Board(b);
b1.makeMove(move, false);
Result val = minimaxVal(b1, d - 1, w, alpha, beta);
if (val.getScore() < bestVal)
{
bestVal = val.getScore();
bestMove = move;
gameCompleted = val.isEndGame();
}
if (bestVal < beta)
{
beta = bestVal;
}
}
}
}
return(new Result(bestMove, bestVal, gameCompleted));
}
//int d is depth of miniMax search. int max should be 1 for getting the max result, -1 for min. Should return moveResult object
public moveResult miniMax(Board b, int d, double timeLimit, int max, Timer timer)
{
//Set up variables
int bestVal = int.MinValue;
int bestMove = 0;
moveResult bestMR = new moveResult(bestMove, bestVal);
//Base case: depth is 0, time is up or game is over. Returns a moveResult with the best score value and 0 move value
if (d == 0 || timeOut || b.gameOver())
{
bestVal = evaluate(b);
//Console.WriteLine("Best score found to be " + bestVal);
moveResult bestMoveResult = new moveResult(bestMove, bestVal);
return(bestMoveResult);
}
if (b.whoseMove() == Position.Top)
{
for (int move = 7; move <= 12; move++)
{
//Console.WriteLine("");
//Recurse if the move is legal, time hasn't expired and game isn't over
int val = 0;
if (b.legalMove(move) && !timeOut && !b.gameOver())
{
Board b1 = new Board(b);
b1.makeMove(move, true);
int newDepth = d - 1;
//Switch the value of max to be the opposite for the recursion
int mnOrMx = max * -1;
//Console.WriteLine("Recursing from " + d + " to " + newDepth + "...");
val = miniMax(b1, newDepth, timeLimit, mnOrMx, timer).getScore();
//If at "max" level, prioritize and return maximum value
if (max == 1)
{
//If there's a new max, update bestValue and bestMove
if (val > bestVal)
{
bestVal = val;
bestMove = move;
}
}
//If at "min" level, prioritize and return minimum value
if (max == -1)
{
//If there's a new min, update bestValue and bestMove
if (val < bestVal || val != int.MinValue)
{
bestVal = val;
bestMove = move;
}
}
}
}
bestMR = new moveResult(bestMove, bestVal);
return(bestMR);
}
else
{
for (int move = 0; move <= 5; move++)
{
//Console.WriteLine("");
//Recurse if the move is legal, time hasn't expired and game isn't over
if (b.legalMove(move) && !timeOut && !b.gameOver())
{
Board b1 = new Board(b);
b1.makeMove(move, true);
int newDepth = d - 1;
//Switch the value of max to be the opposite for the recursion
int mnOrMx = max * -1;
// Console.WriteLine("Recursing from " + d + " to " + newDepth + "...");
int val = miniMax(b1, newDepth, timeLimit, mnOrMx, timer).getScore();
// Console.WriteLine("New Value: " + val);
//If at "max" level, prioritize and return maximum value
if (max == 1)
{
//If there's a new max, update bestValue and bestMove
if (val > bestVal)
{
bestVal = val;
bestMove = move;
}
}
//If at "min" level, prioritize and return minimum value
if (max == -1)
{
//If there's a new min, update bestValue and bestMove
if (val < bestVal || val != int.MinValue)
{
bestVal = val;
bestMove = move;
}
}
}
}
bestMR = new moveResult(bestMove, bestVal);
return(bestMR);
}
//Console.WriteLine("Best move: " + bestMove + " Best score: " + bestVal);
bestMR = new moveResult(bestMove, bestVal);
return(bestMR);
}