/// <summary>
/// A wrapper function to the recursive function, that returns the best action
/// </summary>
/// <param name="control">Control that the state is in</param>
/// <param name="s">The current control state</param>
/// <param name="alpha">Has to be int.MinValue</param>
/// <param name="beta">Has to be int.MaxVakue</param>
/// <param name="player">The player that is maximizing</param>
private Actione BestMove(GameControlBase control, State s, double alpha, double beta, Players player)
{
// This is needed in order to register the next action as the opponent's
Players opponent;
if (player == Players.Player1)
{
opponent = Players.Player2;
}
else
{
opponent = Players.Player1;
}
int maxID = 0;
double maxReward = -1000000;
double Reward = 0;
bool allSame = true; // Are all the rewards the same?
Actione botAction;
State currState = (State)s.Clone(); // Clone the state because it is a reference, so save the original state
for (int i = 0; i < control.ActionNum; i++)
{
if (control.IsLegalAction(new Actione(i), currState))
{
// Make the action as the player
s.Copy(currState);
control.RegisterAction(currState, new Actione(i), player);
if (control.IsTerminalState(currState)) // If its terminal, reward is the reward that the control returns
{
Reward = control.GetReward(player, currState);
}
else // If not terminal, return the minimax recursive function return
{
Reward = 0.9 * GetMaxRewardRec(control, currState, false, opponent, alpha, beta, 1, MaxDepth);
}
if (Reward != maxReward && i != 0) // If the reward changed along the call
{
allSame = false;
}
if (Reward > maxReward)
{
maxID = i;
maxReward = Reward;
}
// Alpha beta pruning
alpha = Math.Max(alpha, maxReward);
if (beta <= alpha)
{
break;
}
}
}
if (!allSame)
{
return(new Actione(maxID));
}
else // If all rewards were the same, do a random action
{
botAction = new Actione(rand.Next(control.ActionNum));
while (!control.IsLegalAction(botAction))
{
botAction = new Actione(rand.Next(control.ActionNum));
}
return(botAction);
}
}
/// <summary>
/// The actual recursive function that return the max reward of a state
/// </summary>
/// <param name="IsMaxing">Is the current player the player that is maximizing</param>
/// <param name="player">The current player</param>
/// <param name="alpha">The best option for maximizing player</param>
/// <param name="beta">The best option for minimizing player</param>
private double GetMaxRewardRec(GameControlBase control, State s, bool IsMaxing, Players player, double alpha, double beta, int level, int maxLevel)
{
// If reached the max depth
if (level > maxLevel)
{
return(0);
}
// This is needed in order to register the next action as the opponent's
Players opponent;
if (player == Players.Player1)
{
opponent = Players.Player2;
}
else
{
opponent = Players.Player1;
}
double BestVal;
double Reward = 0;
State currState = (State)s.Clone();
if (IsMaxing)
{
BestVal = int.MinValue;
for (int i = 0; i < control.ActionNum; i++)
{
if (control.IsLegalAction(new Actione(i), currState))
{
s.Copy(currState);
control.RegisterAction(currState, new Actione(i), player);
if (control.IsTerminalState(currState)) // If its terminal, reward is the reward that the control returns
{
Reward = control.GetReward(player, currState);
}
else // If not terminal, return the minimax recursive function return
{
Reward = 0.9 * GetMaxRewardRec(control, currState, !IsMaxing, opponent, alpha, beta, level + 1, maxLevel);
}
BestVal = Math.Max(Reward, BestVal);
// Alpha beta pruning
alpha = Math.Max(alpha, BestVal);
if (beta <= alpha)
{
break;
}
}
}
}
else
{
BestVal = int.MaxValue;
for (int i = 0; i < control.ActionNum; i++)
{
if (control.IsLegalAction(new Actione(i), currState))
{
s.Copy(currState);
control.RegisterAction(currState, new Actione(i), player);
if (control.IsTerminalState(currState)) // If its terminal, reward is the reward that the control returns
{
Reward = control.GetReward(opponent, currState);
}
else // If not terminal, return the minimax recursive function return
{
Reward = 0.9 * GetMaxRewardRec(control, currState, !IsMaxing, opponent, alpha, beta, level + 1, maxLevel);
}
BestVal = Math.Min(Reward, BestVal);
// Alpha beta pruning
beta = Math.Min(beta, BestVal);
if (beta <= alpha)
{
break;
}
}
}
}
return(BestVal);
}