protected int AlphaBetaMain(int depth, Color color)
{
ChessTreeNode node = new ChessTreeNode()
{
Alpha = -Evaluator.MateValue,
Beta = Evaluator.MateValue,
Depth = depth,
PlayerIndex = (int)color
};
nodesSearched += 1;
bool bSearchPV = true;
var player = this.gameProvider.PlayerBoards[node.PlayerIndex];
var opponent = this.gameProvider.PlayerBoards[1 - node.PlayerIndex];
bool wasKingInCheck = player.IsUnderAttack(player.King.GetSquare(), opponent);
Color currPlayerColor = player.FigureColor;
var movesArray = player.GetMoves(
opponent,
this.gameProvider.History.GetLastMove(),
MovesMask.AllMoves);
this.gameProvider.FilterMoves(movesArray, currPlayerColor);
if (movesArray.Size == 0)
{
this.allocator.ReleaseLast();
if (wasKingInCheck)
{
return(-Evaluator.MateValue + ply);
}
else
{
return(0);
}
}
int score = -Evaluator.MateValue;
bool needsPromotion;
var moves = movesArray.InnerArray;
for (int i = 0; i < movesArray.Size; ++i)
{
var move = moves[i];
this.gameProvider.ProcessMove(move, player.FigureColor);
++ply;
needsPromotion = (int)move.Type >= (int)MoveType.Promotion;
if (needsPromotion)
{
this.gameProvider.PromotePawn(
currPlayerColor,
move.To,
move.Type.GetPromotionFigure());
}
if (bSearchPV)
{
score = -pvSearch(node.GetNext());
}
else
{
score = -zwSearch(node.GetNext());
if (score > node.Alpha)
{
score = -pvSearch(node.GetNext());
}
}
this.gameProvider.CancelLastMove(currPlayerColor);
--ply;
if (score > node.Alpha)
{
node.Alpha = score;
this.bestMove = new Move(move);
bSearchPV = false;
}
}
this.allocator.ReleaseLast();
return(node.Alpha);
}
protected int Quiescence(ChessTreeNode node)
{
nodesSearched += 1;
var player = this.gameProvider.PlayerBoards[node.PlayerIndex];
var opponent = this.gameProvider.PlayerBoards[1 - node.PlayerIndex];
int positionValue = Evaluator.Evaluate(player, opponent);
if (node.Depth < -5)
{
return(positionValue);
}
if (positionValue >= node.Beta)
{
return(node.Beta);
}
if (node.Alpha < positionValue)
{
node.Alpha = positionValue;
}
int score = -Evaluator.MateValue;
Color currPlayerColor = player.FigureColor;
bool wasKingInCheck = player.IsUnderAttack(player.King.GetSquare(), opponent);
var movesArray = player.GetMoves(
opponent,
this.gameProvider.History.GetLastMove(),
MovesMask.Attacks);
this.gameProvider.FilterMoves(movesArray, currPlayerColor);
if (movesArray.Size == 0)
{
if (wasKingInCheck)
{
this.allocator.ReleaseLast();
return((-Evaluator.MateValue) + ply);
}
}
var moves = movesArray.InnerArray;
for (int i = 0; i < movesArray.Size; ++i)
{
var move = moves[i];
this.gameProvider.ProcessMove(move, currPlayerColor);
ply++;
bool needsPromotion = (int)move.Type >= (int)MoveType.Promotion;
if (needsPromotion)
{
this.gameProvider.PromotePawn(
currPlayerColor,
move.To,
move.Type.GetPromotionFigure());
}
score = -Quiescence(node.GetNext());
this.gameProvider.CancelLastMove(currPlayerColor);
ply--;
if (score >= node.Beta)
{
this.allocator.ReleaseLast();
return(node.Beta);
}
if (score > node.Alpha)
{
node.Alpha = score;
}
}
this.allocator.ReleaseLast();
return(node.Alpha);
}