private static void EvalTrappedKnights(Evaluation e, int[] eval, int side, int sq)
{
//look for trapped knights
if (side == 0)
{
if (sq == 7) // white knight on h8
{
if ((e.Board.Pawns[1] & (BitMask.Mask[13] | BitMask.Mask[15])) > 0)
{
eval[0] -= PieceValues[(int)Piece.Knight] / 2; //this trap costs us half a knight
}
}
else if (sq == 0)
{ //white knight on a8
if ((e.Board.Pawns[1] & (BitMask.Mask[8] | BitMask.Mask[10])) > 0)
{
eval[0] -= PieceValues[(int)Piece.Knight] / 2; //this trap costs us half a knight
}
}
else if (sq == 15) //white knight on h7
{
if ((e.Board.Pawns[1] & BitMask.Mask[14]) > 0 &&
(e.Board.Pawns[1] & (BitMask.Mask[23] | BitMask.Mask[21])) > 0)
{
eval[0] -= PieceValues[(int)Piece.Knight] / 2; //this trap costs us half a knight
}
}
else if (sq == 08) //white knight on a7
{
if ((e.Board.Pawns[1] & BitMask.Mask[9]) > 0 &&
(e.Board.Pawns[1] & (BitMask.Mask[16] | BitMask.Mask[18])) > 0)
{
eval[0] -= PieceValues[(int)Piece.Knight] / 2; //this trap costs us half a knight
}
}
}
else
{
if (sq == 63) // black knight on h1
{
if ((e.Board.Pawns[0] & (BitMask.Mask[53] | BitMask.Mask[55])) > 0)
{
eval[1] -= PieceValues[(int)Piece.Knight] / 2; //this trap costs us half a knight
}
}
else if (sq == 56)
{ //black knight on a1
if ((e.Board.Pawns[0] & (BitMask.Mask[48] | BitMask.Mask[50])) > 0)
{
eval[1] -= PieceValues[(int)Piece.Knight] / 2; //this trap costs us half a knight
}
}
else if (sq == 55) //black knight on h2
{
if ((e.Board.Pawns[0] & BitMask.Mask[54]) > 0 &&
(e.Board.Pawns[0] & (BitMask.Mask[45] | BitMask.Mask[47])) > 0)
{
eval[1] -= PieceValues[(int)Piece.Knight] / 2; //this trap costs us half a knight
}
}
else if (sq == 48)//black knight on a2
{
if ((e.Board.Pawns[0] & BitMask.Mask[49]) > 0 &&
(e.Board.Pawns[0] & (BitMask.Mask[40] | BitMask.Mask[42])) > 0)
{
eval[1] -= PieceValues[(int)Piece.Knight] / 2; //this trap costs us half a knight
}
}
}
}
static int EvaluatePieces(Evaluation e)
{
//evaluate things like material imbalance,
//bishop pair, knights supported by pawns, etc.
int[] eval = new int[2];
for (int side = 0; side < 2; side++)
{
int xside = side ^ 1;
//evaluate material imbalances
// a rook+pawn for two pieces is not good
//if side has only one rook and opponent has two
if (e.Board.Rooks[side] > 0 &&
e.Board.Rooks[xside] > 0 &&
e.Board.Rooks[side].Count() == 1 &&
e.Board.Rooks[xside].Count() == 2)
{
//if opposite side has two less minors then we get a bonus
if (e.Board.Minors(side).Count() - e.Board.Minors(xside).Count() == 2)
{
eval[side] += MinorMaterialInbalanceBonus;
}
}
//bishop pair bonus
eval[side] += (e.Board.Bishops[side].Count() == 2) ? BishopPairBonus : 0;
//increase the value of rooks as pawns come off the board
int totalPawns = e.Board.Pawns[0].Count() + e.Board.Pawns[1].Count();
eval[side] += RookBonusPawnCount[totalPawns];
//rooks
var rooks = e.Board.Rooks[side];
while (rooks > 0)
{
int sq = rooks.BitScanForward();
rooks ^= BitMask.Mask[sq];
//open file bonus
if (e.PawnScore.Files[side, sq.File()] == 0)
{
eval[side] += RookOnOpenFileBonus / 2;
if (e.PawnScore.Files[xside, sq.File()] == 0)
{
eval[side] = RookOnOpenFileBonus;
}
}
//rooks on the seventh (or eigth)
if (side == 0 && sq.Rank() <= 1)
{
eval[0] += RookOnSeventhBonus;
}
else if (side == 1 && sq.Rank() >= 6)
{
eval[1] += RookOnSeventhBonus;
}
}
//knights
var knights = e.Board.Knights[side];
while (knights > 0)
{
int sq = knights.BitScanForward();
knights ^= BitMask.Mask[sq];
//only looking for forward knights
if (side == 0 && sq.Rank() > 3)
{
continue;
}
else if (side == 1 && sq.Rank() < 3)
{
continue;
}
//look for knights on outposts
if ((MoveGenerator.PawnAttacks[xside, sq] & e.Board.Pawns[side]) > 0)
{
//knight is defended by a pawn
//use the passed pawn lookup - minus the file to see if
//we have an ouput
if ((PassedPawnMask[side, sq] & ~Board.FileMask[sq.File()] & e.Board.Pawns[xside]) == 0)
{
eval[side] += KnightOnOutpostBonus;
}
}
EvalTrappedKnights(e, eval, side, sq);
}
var bishops = e.Board.Bishops[side];
while (bishops > 0)
{
int sq = bishops.BitScanForward();
bishops ^= BitMask.Mask[sq];
//evaluate trapped bishops
if (side == 0)
{
if (sq == 23 && //white bishop on h6
(e.Board.Pawns[1] & BitMask.Mask[30]) > 0 &&
(e.Board.Pawns[1] & BitMask.Mask[21]) > 0)
{
eval[side] -= PieceValues[(int)Piece.Bishop] / 3;
}
else if (sq == 16 && //white bishop on a6
(e.Board.Pawns[1] & BitMask.Mask[25]) > 0 &&
(e.Board.Pawns[1] & BitMask.Mask[18]) > 0)
{
eval[side] -= PieceValues[(int)Piece.Bishop] / 3;
}
}
else
{
if (sq == 47 && //blackbishop on h3
(e.Board.Pawns[0] & BitMask.Mask[38]) > 0 &&
(e.Board.Pawns[0] & BitMask.Mask[47]) > 0)
{
eval[side] -= PieceValues[(int)Piece.Bishop] / 3;
}
else if (sq == 40 && //black bishop on a3
(e.Board.Pawns[0] & BitMask.Mask[33]) > 0 &&
(e.Board.Pawns[0] & BitMask.Mask[42]) > 0)
{
eval[side] -= PieceValues[(int)Piece.Bishop] / 3;
}
}
//mobility score
var mobilitySquares = MoveGenerator.BishopAttacks(e.Board, sq);
eval[side] += mobilitySquares.Count();
}
}
return(eval[e.Board.SideToMove] - eval[e.Board.SideToMove ^ 1]);
}