EVAL_ESTIMATION EstimateDraw(const Position& pos)
{
static const int FIELD_COLOR[64] =
{
0, 1, 0, 1, 0, 1, 0, 1,
1, 0, 1, 0, 1, 0, 1, 0,
0, 1, 0, 1, 0, 1, 0, 1,
1, 0, 1, 0, 1, 0, 1, 0,
0, 1, 0, 1, 0, 1, 0, 1,
1, 0, 1, 0, 1, 0, 1, 0,
0, 1, 0, 1, 0, 1, 0, 1,
1, 0, 1, 0, 1, 0, 1, 0
};
// KBP-K
if (pos.MatIndex(WHITE) == 3 && pos.Count(PW) == 1)
{
if (pos.MatIndex(BLACK) == 0 && pos.Count(PB) == 0)
{
FLD pawn = Bitboard::LSB(pos.Bits(PW));
FLD bishop = Bitboard::LSB(pos.Bits(BW));
FLD king = pos.King(BLACK);
if (Col(pawn) == 0)
{
if (FIELD_COLOR[A8] != FIELD_COLOR[bishop])
{
if (king == A8 || king == A7 || king == B8 || king == B7)
return EVAL_PRACTICAL_DRAW;
}
}
if (Col(pawn) == 7)
{
if (FIELD_COLOR[H8] != FIELD_COLOR[bishop])
{
if (king == H8 || king == H7 || king == G8 || king == G7)
return EVAL_PRACTICAL_DRAW;
}
}
}
}
if (pos.MatIndex(BLACK) == 3 && pos.Count(PB) == 1)
{
if (pos.MatIndex(WHITE) == 0 && pos.Count(PW) == 0)
{
FLD pawn = Bitboard::LSB(pos.Bits(PB));
FLD bishop = Bitboard::LSB(pos.Bits(BB));
FLD king = pos.King(WHITE);
if (Col(pawn) == 0)
{
if (FIELD_COLOR[A1] != FIELD_COLOR[bishop])
{
if (king == A1 || king == A2 || king == B1 || king == B2)
return EVAL_PRACTICAL_DRAW;
}
}
if (Col(pawn) == 7)
{
if (FIELD_COLOR[H1] != FIELD_COLOR[bishop])
{
if (king == H1 || king == H2 || king == G1 || king == G2)
return EVAL_PRACTICAL_DRAW;
}
}
}
}
// KB-KB
if (pos.MatIndex(WHITE) == 3 && pos.MatIndex(BLACK) == 3)
{
if (pos.Count(BW) == 1 && pos.Count(BB) == 1)
{
FLD bw = Bitboard::LSB(pos.Bits(BW));
FLD bb = Bitboard::LSB(pos.Bits(BB));
if (FIELD_COLOR[bw] != FIELD_COLOR[bb])
return EVAL_PROBABLE_DRAW;
}
}
// LOW MATERIAL
// We can claim draw only in case of "King + minor vs. King".
if (pos.Count(PW) == 0 && pos.Count(PB) == 0)
{
if (pos.MatIndex(WHITE) + pos.MatIndex(BLACK) <= 3)
return EVAL_THEORETICAL_DRAW;
}
// Engames like "King + minor vs. King + minor" - just practical draw,
// but no draw claim, because checkmate positions do exist.
if (pos.Count(PW) == 0 && pos.MatIndex(WHITE) < 5)
{
if (pos.Count(PB) == 0 && pos.MatIndex(BLACK) < 5)
return EVAL_PRACTICAL_DRAW;
else
return EVAL_WHITE_CANNOT_WIN;
}
if (pos.Count(PB) == 0 && pos.MatIndex(BLACK) < 5)
{
if (pos.Count(PW) == 0 && pos.MatIndex(WHITE) < 5)
return EVAL_PRACTICAL_DRAW;
else
return EVAL_BLACK_CANNOT_WIN;
}
return EVAL_UNKNOWN;
}
EVAL Evaluate(const Position& pos, EVAL alpha, EVAL beta)
{
EVAL_ESTIMATION ee = EstimateDraw(pos);
if (ee == EVAL_THEORETICAL_DRAW || ee == EVAL_PRACTICAL_DRAW)
return DRAW_SCORE;
EVAL matScore = pos.Material(WHITE) - pos.Material(BLACK);
if (pos.Count(BW) == 2)
matScore += BishopPair;
if (pos.Count(BB) == 2)
matScore -= BishopPair;
matScore = matScore * g_evalParams.Material / 50;
EVAL lazy = (pos.Side() == WHITE)? matScore : -matScore;
if (lazy <= alpha - g_evalParams.LazyEvalMargin)
return alpha;
if (lazy >= beta + g_evalParams.LazyEvalMargin)
return beta;
EVAL posScore = 0;
EVAL boardScore = 0;
EVAL mobScore = 0;
EVAL pawnStructScore = 0;
EVAL pawnPassedScore = 0;
EVAL kingSafetyScore = 0;
U64 x, y, occ = pos.BitsAll();
FLD f;
//
// PAWNS
//
int index = pos.PawnHash() % g_pawnHashSize;
PawnEntry& pentry = g_pawnHash[index];
if (pentry.m_pawnHash != pos.PawnHash())
pentry.Read(pos);
pawnStructScore += pentry.m_score;
x = pentry.m_passed[WHITE];
while (x)
{
f = Bitboard::PopLSB(x);
if (pos[f - 8] == NOPIECE)
pawnPassedScore += PAWN_PASSED_FREE[7 - Row(f)];
else
pawnPassedScore += PAWN_PASSED_BLOCKED[7 - Row(f)];
if (pos.MatIndex(BLACK) == 0)
{
FLD f1 = f;
if (pos.Side() == BLACK)
f1 += 8;
if ((Bitboard::PawnSquare(f1, WHITE) & pos.Bits(KB)) == 0)
pawnPassedScore += PawnPassedSquare * (7 - Row(f1)) / 6;
}
else if (pos.MatIndex(BLACK) < 10)
pawnPassedScore += PassedKingDist * Dist(f - 8, pos.King(BLACK));
}
x = pentry.m_passed[BLACK];
while (x)
{
f = Bitboard::PopLSB(x);
if (pos[f + 8] == NOPIECE)
pawnPassedScore -= PAWN_PASSED_FREE[Row(f)];
else
pawnPassedScore -= PAWN_PASSED_BLOCKED[Row(f)];
if (pos.MatIndex(WHITE) == 0)
{
FLD f1 = f;
if (pos.Side() == WHITE)
f1 -= 8;
if ((Bitboard::PawnSquare(f1, BLACK) & pos.Bits(KW)) == 0)
pawnPassedScore -= PawnPassedSquare * Row(f1) / 6;
}
else if (pos.MatIndex(WHITE) < 10)
pawnPassedScore -= PassedKingDist * Dist(f + 8, pos.King(WHITE));
}
//
// KNIGHTS
//
static const int outpost[64] =
{
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 1, 1, 0, 0, 0,
0, 0, 1, 1, 1, 1, 0, 0,
0, 1, 1, 1, 1, 1, 1, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0
};
static const int knight_mob[64] =
{
2, 3, 4, 4, 4, 4, 3, 2,
3, 4, 6, 6, 6, 6, 4, 2,
4, 6, 8, 8, 8, 8, 6, 4,
4, 6, 8, 8, 8, 8, 6, 4,
4, 6, 8, 8, 8, 8, 6, 4,
4, 6, 8, 8, 8, 8, 6, 4,
3, 4, 6, 6, 6, 6, 4, 2,
2, 3, 4, 4, 4, 4, 3, 2
};
x = pos.Bits(NW);
while (x)
{
f = Bitboard::PopLSB(x);
boardScore += PSQ_N[f];
int mob = knight_mob[f];
mobScore += KNIGHT_MOBILITY[mob];
if (outpost[f])
{
if (Bitboard::PawnAttacks(f, BLACK) & pos.Bits(PW))
boardScore += KnightOutpost;
}
}
x = pos.Bits(NB);
while (x)
{
f = Bitboard::PopLSB(x);
boardScore -= PSQ_N[FLIP[f]];
int mob = knight_mob[f];
mobScore -= KNIGHT_MOBILITY[mob];
if (outpost[FLIP[f]])
{
if (Bitboard::PawnAttacks(f, WHITE) & pos.Bits(PB))
boardScore -= KnightOutpost;
}
}
//
// BISHOPS
//
x = pos.Bits(BW);
while (x)
{
f = Bitboard::PopLSB(x);
boardScore += PSQ_B[f];
y = Bitboard::BishopAttacks(f, occ);
mobScore += BISHOP_MOBILITY[Bitboard::CountBits(y)];
}
x = pos.Bits(BB);
while (x)
{
f = Bitboard::PopLSB(x);
boardScore -= PSQ_B[FLIP[f]];
y = Bitboard::BishopAttacks(f, occ);
mobScore -= BISHOP_MOBILITY[Bitboard::CountBits(y)];
}
//
// ROOKS
//
x = pos.Bits(RW);
while (x)
{
f = Bitboard::PopLSB(x);
y = Bitboard::RookAttacks(f, occ ^ pos.Bits(RW));
mobScore += ROOK_MOBILITY[Bitboard::CountBits(y)];
if (Row(f) == 1)
boardScore += Rook7th;
int file = Col(f) + 1;
if (pentry.m_ranks[file][WHITE] == 0)
boardScore += RookOpen;
}
x = pos.Bits(RB);
while (x)
{
f = Bitboard::PopLSB(x);
y = Bitboard::RookAttacks(f, occ ^ pos.Bits(RB));
mobScore -= ROOK_MOBILITY[Bitboard::CountBits(y)];
if (Row(f) == 6)
boardScore -= Rook7th;
int file = Col(f) + 1;
if (pentry.m_ranks[file][BLACK] == 7)
boardScore -= RookOpen;
}
//
// QUEENS
//
x = pos.Bits(QW);
while (x)
{
f = Bitboard::PopLSB(x);
kingSafetyScore += QUEEN_KING_TROPISM[Dist(f, pos.King(BLACK))];
}
x = pos.Bits(QB);
while (x)
{
f = Bitboard::PopLSB(x);
kingSafetyScore -= QUEEN_KING_TROPISM[Dist(f, pos.King(WHITE))];
}
//
// KINGS
//
{
f = pos.King(WHITE);
kingSafetyScore += PSQ_K_MID[f] * pos.MatIndex(BLACK) / 32;
boardScore += PSQ_K_END[f] * (32 - pos.MatIndex(BLACK)) / 32;
int penalty = PawnShieldWhite(pentry, f);
kingSafetyScore += KING_PAWN_SHIELD[penalty] * pos.MatIndex(BLACK) / 32;
}
{
f = pos.King(BLACK);
kingSafetyScore -= PSQ_K_MID[FLIP[f]] * pos.MatIndex(WHITE) / 32;
boardScore -= PSQ_K_END[FLIP[f]] * (32 - pos.MatIndex(WHITE)) / 32;
int penalty = PawnShieldBlack(pentry, f);
kingSafetyScore -= KING_PAWN_SHIELD[penalty] * pos.MatIndex(WHITE) / 32;
}
posScore += mobScore * g_evalParams.Mobility / 50;
posScore += pawnStructScore * g_evalParams.PawnStruct / 50;
posScore += pawnPassedScore * g_evalParams.PawnPassed / 50;
posScore += kingSafetyScore * g_evalParams.KingSafety / 50;
posScore += boardScore * g_evalParams.BoardControl / 50;
EVAL e = matScore + posScore;
if (e > 0 && ee == EVAL_WHITE_CANNOT_WIN)
e = 0;
if (e < 0 && ee == EVAL_BLACK_CANNOT_WIN)
e = 0;
if (ee == EVAL_PROBABLE_DRAW)
e /= 2;
return (pos.Side() == WHITE)? e : -e;
}