// weight_option() computes the value of an evaluation weight, by combining
// two UCI-configurable weights (midgame and endgame) with an internal weight.
public static WeightS weight_option(string mgOpt, string egOpt, Score internalWeight)
{
WeightS w = new WeightS(Engine.Options[mgOpt].getInt() * Types.mg_value(internalWeight) / 100,
Engine.Options[egOpt].getInt() * Types.eg_value(internalWeight) / 100);
return(w);
}
// do_evaluate() is the evaluation entry point, called directly from evaluate()
public static Value do_evaluate(Position pos, bool Trace)
{
Debug.Assert(0 == pos.checkers());
EvalInfo ei = new EvalInfo();
Score score;
Score[] mobility = new Score[] { ScoreS.SCORE_ZERO, ScoreS.SCORE_ZERO };
Thread thisThread = pos.this_thread();
// Initialize score by reading the incrementally updated scores included
// in the position object (material + piece square tables) and adding a
// Tempo bonus. Score is computed from the point of view of white.
score = pos.psq_score() + (pos.side_to_move() == ColorS.WHITE ? Tempo : -Tempo);
// Probe the material hash table
ei.mi = Material.probe(pos, thisThread.materialTable, thisThread.endgames);
score += ei.mi.material_value();
// If we have a specialized evaluation function for the current material
// configuration, call it and return.
if (ei.mi.specialized_eval_exists())
{
return(ei.mi.evaluate(pos));
}
// Probe the pawn hash table
ei.pi = Pawns.probe(pos, thisThread.pawnsTable);
score += apply_weight(ei.pi.pawns_value(), Weights[EvalWeightS.PawnStructure]);
// Initialize attack and king safety bitboards
init_eval_info(pos, ei, ColorS.WHITE);
init_eval_info(pos, ei, ColorS.BLACK);
ei.attackedBy[ColorS.WHITE][PieceTypeS.ALL_PIECES] |= ei.attackedBy[ColorS.WHITE][PieceTypeS.KING];
ei.attackedBy[ColorS.BLACK][PieceTypeS.ALL_PIECES] |= ei.attackedBy[ColorS.BLACK][PieceTypeS.KING];
// Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
Bitboard[] mobilityArea = new Bitboard[] { ~(ei.attackedBy[ColorS.BLACK][PieceTypeS.PAWN] | pos.pieces_color_piecetype(ColorS.WHITE, PieceTypeS.PAWN, PieceTypeS.KING)),
~(ei.attackedBy[ColorS.WHITE][PieceTypeS.PAWN] | pos.pieces_color_piecetype(ColorS.BLACK, PieceTypeS.PAWN, PieceTypeS.KING)) };
// Evaluate pieces and mobility
score += evaluate_pieces(pos, ei, mobility, mobilityArea, PieceTypeS.KNIGHT, ColorS.WHITE, Trace);
score += Eval.apply_weight(mobility[ColorS.WHITE] - mobility[ColorS.BLACK], Weights[EvalWeightS.Mobility]);
// Evaluate kings after all other pieces because we need complete attack
// information when computing the king safety evaluation.
score += evaluate_king(pos, ei, ColorS.WHITE, Trace)
- evaluate_king(pos, ei, ColorS.BLACK, Trace);
// Evaluate tactical threats, we need full attack information including king
score += evaluate_threats(pos, ei, ColorS.WHITE, Trace)
- evaluate_threats(pos, ei, ColorS.BLACK, Trace);
// Evaluate passed pawns, we need full attack information including king
score += evaluate_passed_pawns(pos, ei, ColorS.WHITE, Trace)
- evaluate_passed_pawns(pos, ei, ColorS.BLACK, Trace);
// If one side has only a king, check whether exists any unstoppable passed pawn
if (0 == pos.non_pawn_material(ColorS.WHITE) || 0 == pos.non_pawn_material(ColorS.BLACK))
{
score += evaluate_unstoppable_pawns(pos, ColorS.WHITE, ei)
- evaluate_unstoppable_pawns(pos, ColorS.BLACK, ei);
}
// Evaluate space for both sides, only in middle-game.
if (ei.mi.space_weight() != 0)
{
int s = evaluate_space(pos, ei, ColorS.WHITE) - evaluate_space(pos, ei, ColorS.BLACK);
score += Eval.apply_weight(s * ei.mi.space_weight(), Weights[EvalWeightS.Space]);
}
// Scale winning side if position is more drawish that what it appears
ScaleFactor sf = Types.eg_value(score) > ValueS.VALUE_DRAW ? ei.mi.scale_factor(pos, ColorS.WHITE)
: ei.mi.scale_factor(pos, ColorS.BLACK);
// If we don't already have an unusual scale factor, check for opposite
// colored bishop endgames, and use a lower scale for those.
if (ei.mi.game_phase() < PhaseS.PHASE_MIDGAME &&
pos.opposite_bishops() &&
(sf == ScaleFactorS.SCALE_FACTOR_NORMAL || sf == ScaleFactorS.SCALE_FACTOR_ONEPAWN))
{
// Ignoring any pawns, do both sides only have a single bishop and no
// other pieces?
if (pos.non_pawn_material(ColorS.WHITE) == ValueS.BishopValueMg &&
pos.non_pawn_material(ColorS.BLACK) == ValueS.BishopValueMg)
{
// Check for KBP vs KB with only a single pawn that is almost
// certainly a draw or at least two pawns.
bool one_pawn = (pos.count(ColorS.WHITE, PieceTypeS.PAWN) + pos.count(ColorS.BLACK, PieceTypeS.PAWN) == 1);
sf = one_pawn ? (8) : (32);
}
else
{
// Endgame with opposite-colored bishops, but also other pieces. Still
// a bit drawish, but not as drawish as with only the two bishops.
sf = (50 * sf / ScaleFactorS.SCALE_FACTOR_NORMAL);
}
}
// Interpolate between a middlegame and a (scaled by 'sf') endgame score
Value v = Types.mg_value(score) * (ei.mi.game_phase())
+ Types.eg_value(score) * (PhaseS.PHASE_MIDGAME - ei.mi.game_phase()) * sf / ScaleFactorS.SCALE_FACTOR_NORMAL;
v /= (PhaseS.PHASE_MIDGAME);
// In case of tracing add all single evaluation contributions for both white and black
if (Trace)
{
//Tracing.add_term(Tracing.PST, pos.psq_score());
//Tracing.add_term(Tracing.IMBALANCE, ei.mi.material_value());
//Tracing.add_term(PAWN, ei.pi.pawns_value());
//Tracing.add_term(Tracing.MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
// , apply_weight(mobility[BLACK], Weights[Mobility]));
//Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
//Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
//Tracing.add_term(Tracing.SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
//Tracing.add_term(Tracing.TOTAL, score);
//Tracing.ei = ei;
//Tracing.sf = sf;
}
return(pos.side_to_move() == ColorS.WHITE ? v : -v);
}
// evaluate_king() assigns bonuses and penalties to a king of a given color
public static Score evaluate_king(Position pos, EvalInfo ei, Color Us, bool Trace)
{
Color Them = (Us == ColorS.WHITE ? ColorS.BLACK : ColorS.WHITE);
Bitboard undefended, b, b1, b2, safe;
int attackUnits;
Square ksq = pos.king_square(Us);
// King shelter and enemy pawns storm
Score score = ei.pi.king_safety(pos, ksq, Us);
// Main king safety evaluation
if (ei.kingAttackersCount[Them] != 0)
{
// Find the attacked squares around the king which have no defenders
// apart from the king itself
undefended = ei.attackedBy[Them][PieceTypeS.ALL_PIECES]
& ei.attackedBy[Us][PieceTypeS.KING]
& ~(ei.attackedBy[Us][PieceTypeS.PAWN] | ei.attackedBy[Us][PieceTypeS.KNIGHT]
| ei.attackedBy[Us][PieceTypeS.BISHOP] | ei.attackedBy[Us][PieceTypeS.ROOK]
| ei.attackedBy[Us][PieceTypeS.QUEEN]);
// Initialize the 'attackUnits' variable, which is used later on as an
// index to the KingDanger[] array. The initial value is based on the
// number and types of the enemy's attacking pieces, the number of
// attacked and undefended squares around our king and the quality of
// the pawn shelter (current 'score' value).
attackUnits = Math.Min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
+ 3 * (ei.kingAdjacentZoneAttacksCount[Them] + Bitcount.popcount_Max15(undefended))
+ 2 * (ei.pinnedPieces[Us] != 0 ? 1 : 0)
- Types.mg_value(score) / 32;
// Analyse the enemy's safe queen contact checks. Firstly, find the
// undefended squares around the king that are attacked by the enemy's
// queen...
b = undefended & ei.attackedBy[Them][PieceTypeS.QUEEN] & ~pos.pieces_color(Them);
if (b != 0)
{
// ...and then remove squares not supported by another enemy piece
b &= (ei.attackedBy[Them][PieceTypeS.PAWN] | ei.attackedBy[Them][PieceTypeS.KNIGHT]
| ei.attackedBy[Them][PieceTypeS.BISHOP] | ei.attackedBy[Them][PieceTypeS.ROOK]);
if (b != 0)
{
attackUnits += QueenContactCheck
* Bitcount.popcount_Max15(b)
* (Them == pos.side_to_move() ? 2 : 1);
}
}
// Analyse the enemy's safe rook contact checks. Firstly, find the
// undefended squares around the king that are attacked by the enemy's
// rooks...
b = undefended & ei.attackedBy[Them][PieceTypeS.ROOK] & ~pos.pieces_color(Them);
// Consider only squares where the enemy rook gives check
b &= BitBoard.PseudoAttacks[PieceTypeS.ROOK][ksq];
if (b != 0)
{
// ...and then remove squares not supported by another enemy piece
b &= (ei.attackedBy[Them][PieceTypeS.PAWN] | ei.attackedBy[Them][PieceTypeS.KNIGHT]
| ei.attackedBy[Them][PieceTypeS.BISHOP] | ei.attackedBy[Them][PieceTypeS.QUEEN]);
if (b != 0)
{
attackUnits += RookContactCheck
* Bitcount.popcount_Max15(b)
* (Them == pos.side_to_move() ? 2 : 1);
}
}
// Analyse enemy's safe distance checks for sliders and knights
safe = ~(pos.pieces_color(Them) | ei.attackedBy[Us][PieceTypeS.ALL_PIECES]);
b1 = pos.attacks_from_square_piecetype(ksq, PieceTypeS.ROOK) & safe;
b2 = pos.attacks_from_square_piecetype(ksq, PieceTypeS.BISHOP) & safe;
// Enemy queen safe checks
b = (b1 | b2) & ei.attackedBy[Them][PieceTypeS.QUEEN];
if (b != 0)
{
attackUnits += QueenCheck * Bitcount.popcount_Max15(b);
}
// Enemy rooks safe checks
b = b1 & ei.attackedBy[Them][PieceTypeS.ROOK];
if (b != 0)
{
attackUnits += RookCheck * Bitcount.popcount_Max15(b);
}
// Enemy bishops safe checks
b = b2 & ei.attackedBy[Them][PieceTypeS.BISHOP];
if (b != 0)
{
attackUnits += BishopCheck * Bitcount.popcount_Max15(b);
}
// Enemy knights safe checks
b = pos.attacks_from_square_piecetype(ksq, PieceTypeS.KNIGHT) & ei.attackedBy[Them][PieceTypeS.KNIGHT] & safe;
if (b != 0)
{
attackUnits += KnightCheck * Bitcount.popcount_Max15(b);
}
// To index KingDanger[] attackUnits must be in [0, 99] range
attackUnits = Math.Min(99, Math.Max(0, attackUnits));
// Finally, extract the king danger score from the KingDanger[]
// array and subtract the score from evaluation.
score -= KingDanger[Us == Search.RootColor ? 1 : 0][attackUnits];
}
if (Trace)
{
Tracing.terms[Us][PieceTypeS.KING] = score;
}
return(score);
}
public static Score[][] KingDanger = new Score[ColorS.COLOR_NB][] { new Score[128], new Score[128] }; // 2, 128
// apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
public static Score apply_weight(Score v, WeightS w)
{
return(Types.make_score(Types.mg_value(v) * w.mg / 256, Types.eg_value(v) * w.eg / 256));
}
