const Value BishopPairMidgameBonus = Value(109);
const Value BishopPairEndgameBonus = Value(97);
- Key KNNKMaterialKey, KKNNMaterialKey;
+ // Polynomial material balance parameters
+ const Value RedundantQueenPenalty = Value(320);
+ const Value RedundantRookPenalty = Value(554);
+ const int LinearCoefficients[6] = { 1709, -137, -1185, -166, 141, 59 };
+
+ const int QuadraticCoefficientsSameColor[][6] = {
+ { 0, 0, 0, 0, 0, 0 }, { 33, -6, 0, 0, 0, 0 }, { 29, 269, -12, 0, 0, 0 },
+ { 0, 19, -4, 0, 0, 0 }, { -35, -10, 40, 95, 50, 0 }, { 52, 23, 78, 144, -11, -33 } };
+
+ const int QuadraticCoefficientsOppositeColor[][6] = {
+ { 0, 0, 0, 0, 0, 0 }, { -5, 0, 0, 0, 0, 0 }, { -33, 23, 0, 0, 0, 0 },
+ { 17, 25, -3, 0, 0, 0 }, { 10, -2, -19, -67, 0, 0 }, { 69, 64, -41, 116, 137, 0 } };
// Unmapped endgame evaluation and scaling functions, these
// are accessed direcly and not through the function maps.
ScalingFunction<KQKRP> ScaleKQKRP(WHITE), ScaleKRPKQ(BLACK);
ScalingFunction<KPsK> ScaleKPsK(WHITE), ScaleKKPs(BLACK);
ScalingFunction<KPKP> ScaleKPKPw(WHITE), ScaleKPKPb(BLACK);
+
+ Key KNNKMaterialKey, KKNNMaterialKey;
}
// Evaluate the material balance
- Color c;
+ const int bishopsPair_count[2] = { pos.piece_count(WHITE, BISHOP) > 1, pos.piece_count(BLACK, BISHOP) > 1 };
+ Color c, them;
int sign;
- Value egValue = Value(0);
- Value mgValue = Value(0);
+ int matValue = 0;
for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
{
}
}
- // Bishop pair
- if (pos.piece_count(c, BISHOP) >= 2)
- {
- mgValue += sign * BishopPairMidgameBonus;
- egValue += sign * BishopPairEndgameBonus;
- }
-
- // Knights are stronger when there are many pawns on the board. The
- // formula is taken from Larry Kaufman's paper "The Evaluation of Material
- // Imbalances in Chess":
+ // Redundancy of major pieces, formula based on Kaufman's paper
+ // "The Evaluation of Material Imbalances in Chess"
// http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
- mgValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
- egValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
-
- // Redundancy of major pieces, again based on Kaufman's paper:
if (pos.piece_count(c, ROOK) >= 1)
+ matValue -= sign * ((pos.piece_count(c, ROOK) - 1) * RedundantRookPenalty + pos.piece_count(c, QUEEN) * RedundantQueenPenalty);
+
+ // Second-degree polynomial material imbalance by Tord Romstad
+ //
+ // We use NO_PIECE_TYPE as a place holder for the bishop pair "extended piece",
+ // this allow us to be more flexible in defining bishop pair bonuses.
+ them = opposite_color(c);
+ for (PieceType pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; pt1++)
{
- Value v = Value((pos.piece_count(c, ROOK) - 1) * 32 + pos.piece_count(c, QUEEN) * 16);
- mgValue -= sign * v;
- egValue -= sign * v;
+ int c1, c2, c3;
+ c1 = sign * (pt1 != NO_PIECE_TYPE ? pos.piece_count(c, pt1) : bishopsPair_count[c]);
+ if (!c1)
+ continue;
+
+ matValue += c1 * LinearCoefficients[pt1];
+
+ for (PieceType pt2 = NO_PIECE_TYPE; pt2 <= pt1; pt2++)
+ {
+ c2 = (pt2 != NO_PIECE_TYPE ? pos.piece_count(c, pt2) : bishopsPair_count[c]);
+ c3 = (pt2 != NO_PIECE_TYPE ? pos.piece_count(them, pt2) : bishopsPair_count[them]);
+ matValue += c1 * c2 * QuadraticCoefficientsSameColor[pt1][pt2];
+ matValue += c1 * c3 * QuadraticCoefficientsOppositeColor[pt1][pt2];
+ }
}
}
- mi->mgValue = int16_t(mgValue);
- mi->egValue = int16_t(egValue);
+
+ mi->value = int16_t(matValue / 16);
return mi;
}
public:
MaterialInfo() : key(0) { clear(); }
- Value mg_value() const;
- Value eg_value() const;
+ Value material_value() const;
ScaleFactor scale_factor(const Position& pos, Color c) const;
int space_weight() const;
bool specialized_eval_exists() const;
inline void clear();
Key key;
- int16_t mgValue;
- int16_t egValue;
+ int16_t value;
uint8_t factor[2];
EndgameEvaluationFunctionBase* evaluationFunction;
EndgameScalingFunctionBase* scalingFunction[2];
//// Inline functions
////
-/// MaterialInfo::mg_value and MaterialInfo::eg_value simply returns the
-/// material balance evaluation for the middle game and the endgame.
+/// MaterialInfo::material_value simply returns the material balance
+/// evaluation that is independent from game phase.
-inline Value MaterialInfo::mg_value() const {
+inline Value MaterialInfo::material_value() const {
- return Value(mgValue);
-}
-
-inline Value MaterialInfo::eg_value() const {
-
- return Value(egValue);
+ return Value(value);
}
inline void MaterialInfo::clear() {
- mgValue = egValue = 0;
+ value = 0;
factor[WHITE] = factor[BLACK] = uint8_t(SCALE_FACTOR_NORMAL);
evaluationFunction = NULL;
scalingFunction[WHITE] = scalingFunction[BLACK] = NULL;