/* Evaluation heurisitc:
* Consider each potential winning line. If there is a black piece
* in the line, then it cannot be won by white, so score that line as zero.
* Otherwise, score the line as the # of white pieces residing in the line.
* Keep track of the highest scoring chain, and how many were found with
* that score. Do the same for black.
*
* Give most favor to longer chains, then secondary favor to the number of
* such chains present. Create a positive white score this way, then
* subtract off the corresponding black score using the same logic.
*
* Always gives positive score to white, negative to black. Up to the
* caller to multiply by -1 if needed.
*/
private static int EvaluateChains(ref Board b)
{
int longestWhiteChain = 0;
int numLongestWhiteChain = 0;
int longestBlackChain = 0;
int numLongestBlackChain = 0;
UInt64 whiteTemp, blackTemp;
int temp;
for (int i = 0; i < BoardHelper.WinningLines.Length; i++)
{
// how many white pieces are in this line
whiteTemp = b.WhiteBitBoard & BoardHelper.WinningLines[i];
// how many black pieces are in this line
blackTemp = b.BlackBitBoard & BoardHelper.WinningLines[i];
if (blackTemp == 0 && whiteTemp != 0)
{
temp = BoardHelper.NumCommonOneBits(b.WhiteBitBoard, BoardHelper.WinningLines[i]);
if (temp >= longestWhiteChain)
{
if (temp == longestWhiteChain)
{
numLongestWhiteChain++;
}
else
{
longestWhiteChain = temp;
numLongestWhiteChain = 1;
}
}
continue; // no need to evaluate black
}
if (whiteTemp == 0 && blackTemp != 0)
{
temp = BoardHelper.NumCommonOneBits(b.BlackBitBoard, BoardHelper.WinningLines[i]);
if (temp >= longestBlackChain)
{
if (temp == longestBlackChain)
{
numLongestBlackChain++;
}
else
{
longestBlackChain = temp;
numLongestBlackChain = 1;
}
}
}
}
return((100 * longestWhiteChain + numLongestWhiteChain) - (100 * longestBlackChain + numLongestBlackChain));
}
public static bool HasCheckmate(Board b, PieceColor pieceColor)
{
int whiteTemp = 0;
int blackTemp = 0;
UInt64 whiteLine = 0;
UInt64 blackLine = 0;
List <UInt64> lines = new List <UInt64>();
for (int i = 0; i < BoardHelper.WinningLines.Length; i++)
{
whiteLine = b.WhiteBitBoard & BoardHelper.WinningLines[i];
whiteTemp = BoardHelper.NumOneBits(whiteLine);
blackLine = b.BlackBitBoard & BoardHelper.WinningLines[i];
blackTemp = BoardHelper.NumOneBits(blackLine);
if (pieceColor == PieceColor.White && blackTemp == 0 && whiteTemp == 4)
{
foreach (UInt64 line in lines)
{
if (line == whiteLine)
{
return(true);
}
}
lines.Add(whiteLine);
}
else if (pieceColor == PieceColor.Black && whiteTemp == 0 && blackTemp == 4)
{
foreach (UInt64 line in lines)
{
if (line == blackLine)
{
return(true);
}
}
lines.Add(blackLine);
}
}
return(false);
}