static PawnScore EvaluatePawns(Board b)
{
int[] eval = new int[2];
var fileMask = Board.FileMask;
var returnVal = new PawnScore();
for (int side = 0; side < 2; side++)
{
ulong pawns = b.Pawns[side];
int xside = side ^ 1;
ulong opponentPawns = b.Pawns[side ^ 1];
//evaluate file by file
for (int i = 0; i < 8; i++)
{
returnVal.Files[side, i] = pawns & Board.FileMask[i];
returnVal.Files[xside, i] = opponentPawns & Board.FileMask[i];
//evaluate my doubled pawns
if (returnVal.Files[side, i].Count() > 1)
{
//doubled pawns
if (i > 0 && i < 7) //ignoring outside pawns
//check for isolated doubled pawns
{
if ((pawns & Board.FileMask[i - 1]) == 0 &&
(pawns & Board.FileMask[i + 1]) == 0)
{
eval[side] += 4 * DoubledPawnPenalty;
}
else
{
eval[side] += 2 * DoubledPawnPenalty;
}
}
}
}
//individual pawns
var p = pawns;
while (p > 0)
{
var pawnsq = p.BitScanForward();
p ^= BitMask.Mask[pawnsq];
//passed pawns
if ((PassedPawnMask[side, pawnsq] & opponentPawns) == 0)
{
var distanceMultiplier = side == 1 ? pawnsq.Rank() : 8 - pawnsq.Rank();
eval[side] +=
PassedPawnBonus * distanceMultiplier;
}
//blocked pawns
if (side == 0 && pawnsq > 7)
{
if ((b.AllPieces & BitMask.Mask[pawnsq - 8]) > 0)
{
eval[side] += BlockedPawnPenalty;
}
else if (side == 1 && pawnsq < 56)
{
if ((b.AllPieces & BitMask.Mask[pawnsq + 8]) > 0)
{
eval[side] += BlockedPawnPenalty;
}
}
}
}
}
returnVal.Eval = eval[b.SideToMove] - eval[b.SideToMove ^ 1];
return(returnVal);
}
static int EvaluateKingSafety(Board b, PawnScore pawnScore)
{
int[] eval = new int[2];
for (int side = 0; side < 2; side++)
{
var xside = side ^ 1;
if ((kingside & b.King[side]) > 0)
{ // if my king is on the kingside
if ((b.Rooks[side] & Board.FileMask[7]) > 0) // if I have a rook in the corner
{
//if the opponent has a queen and rook on the board, evaluate castle status
if ((b.Queens[xside] > 0) &&
(b.Rooks[xside] > 0))
{
eval[side] += NotCastledPenalty;
}
}
else
{
//king looks safely tucked
//evaluate the pawns in front of my king
for (int f = 5; f < 8; f++)
{
//if I have no pawns on the file
if (pawnScore.Files[side, f] == 0)
{
eval[side] += OpenFileInFrontOfCastledKingPenalty;
// //look for case where the opponent has an opening
// //and a major piece, and has not castled in that direction
// if (pawnScore.Files[xside, f] == 0 && //opponent has opened the file
// ((b.Rooks[xside] | b.Queens[xside]) & Board.FileMask[f]) > 0 && //heavypiece
// ((b.King[xside] & queenside) > 0))//opponents king is safely on the other side
// {
// //major probjem
// eval[side] += KingUnderAttack;
// }
}
}
}
}
else if ((queenside & b.King[side]) > 0)
{
//my king is on the queenside
if ((b.Rooks[side] & Board.FileMask[0]) > 0) //there is a rook in the corner
{
//if the opponent has a queen and rook on the board, evaluate castle status
if ((b.Queens[xside] > 0) &&
(b.Rooks[xside] > 0))
{
eval[side] += NotCastledPenalty;
}
}
else
{
//king is tucked
//evaluate the pawns in front of my king
for (int f = 2; f >= 0; f--)
{
//if I have no pawns on the file
if (pawnScore.Files[side, f] == 0)
{
eval[side] += OpenFileInFrontOfCastledKingPenalty;
// //look for case where the opponent has an opening
// //and a major piece, and has not castled in that direction
// if (pawnScore.Files[xside, f] == 0 && //opponent has opened the file
// ((b.Rooks[xside] | b.Queens[xside]) & kingside) > 0 && //heavypiece
// ((b.King[xside] & kingside) > 0)) //opponents king is safely on the other side
// {
// //major probjem
// eval[side] += KingUnderAttack;
// }
}
}
}
}
else
{
//king is in the middle of the board
if ((b.Queens[xside] > 0) &&
(b.Rooks[xside] > 0))
{
eval[side] += NotCastledPenalty;
}
}
}
return(eval[b.SideToMove] - eval[b.SideToMove ^ 1]);
}
