/// evaluate() is the main evaluation function. It always computes two
/// values, an endgame score and a middle game score, and interpolates
/// between them based on the remaining material.
internal static int do_evaluate(bool Trace, Position pos, ref int margin)
{
Debug.Assert(!pos.in_check());
var ei = EvalInfoBroker.GetObject();
Value marginsWHITE, marginsBLACK;
int score = 0, mobilityWhite = 0, mobilityBlack = 0;
// margins[] store the uncertainty estimation of position's evaluation
// that typically is used by the search for pruning decisions.
marginsWHITE = marginsBLACK = ValueC.VALUE_ZERO;
// Initialize score by reading the incrementally updated scores included
// in the position object (material + piece square tables) and adding
// Tempo bonus. Score is computed from the point of view of white.
score = pos.st.psqScore + (pos.sideToMove == ColorC.WHITE ? Tempo : -Tempo);
// Probe the material hash table
pos.this_thread().materialTable.probe(pos, out ei.mi);
score += ((ei.mi.value << 16) + ei.mi.value);
// If we have a specialized evaluation function for the current material
// configuration, call it and return.
if (ei.mi.evaluationFunction != null)
{
margin = ValueC.VALUE_ZERO;
var retval = ei.mi.evaluationFunction(ei.mi.evaluationFunctionColor, pos);
ei.pi = null;
ei.mi = null;
EvalInfoBroker.Free();
return retval;
}
// Probe the pawn hash table
pos.this_thread().pawnTable.probe(pos, out ei.pi);
score += ei.pi.value;
// Initialize attack and king safety bitboards
init_eval_info(ColorC.WHITE, pos, ei);
init_eval_info(ColorC.BLACK, pos, ei);
// Evaluate pieces and mobility
score += evaluate_pieces_of_color(ColorC.WHITE, Trace, pos, ei, ref mobilityWhite)
- evaluate_pieces_of_color(ColorC.BLACK, Trace, pos, ei, ref mobilityBlack);
score += (((((((mobilityWhite - mobilityBlack) + 32768) & ~0xffff) / 0x10000
* (((Weights[EvalWeightC.Mobility] + 32768) & ~0xffff) / 0x10000)) / 0x100) << 16)
+ (((short)((mobilityWhite - mobilityBlack) & 0xffff)
* ((short)(Weights[EvalWeightC.Mobility] & 0xffff))) / 0x100));
// Evaluate kings after all other pieces because we need complete attack
// information when computing the king safety evaluation.
score += evaluate_king(ColorC.WHITE, Trace, pos, ei, ref marginsWHITE, ref marginsBLACK)
- evaluate_king(ColorC.BLACK, Trace, pos, ei, ref marginsWHITE, ref marginsBLACK);
// Evaluate tactical threats, we need full attack information including king
score += evaluate_threats(ColorC.WHITE, pos, ei) - evaluate_threats(ColorC.BLACK, pos, ei);
// Evaluate passed pawns, we need full attack information including king
score += evaluate_passed_pawns(ColorC.WHITE, pos, ei) - evaluate_passed_pawns(ColorC.BLACK, pos, ei);
// If one side has only a king, check whether exists any unstoppable passed pawn
if ((pos.st.npMaterialWHITE == 0) || (pos.st.npMaterialBLACK == 0))
{
score += evaluate_unstoppable_pawns(pos, ei);
}
// Evaluate space for both sides, only in middle-game.
if (ei.mi.spaceWeight != 0)
{
var s = evaluate_space(ColorC.WHITE, pos, ei) - evaluate_space(ColorC.BLACK, pos, ei);
score += ((((((((s * ei.mi.spaceWeight) << 16) + 32768) & ~0xffff) / 0x10000
* (((Weights[EvalWeightC.Space] + 32768) & ~0xffff) / 0x10000)) / 0x100) << 16)
+ (((short)(((s * ei.mi.spaceWeight) << 16) & 0xffff)
* ((short)(Weights[EvalWeightC.Space] & 0xffff))) / 0x100));
}
// Scale winning side if position is more drawish that what it appears
var sf = ((short)(score & 0xffff)) > ValueC.VALUE_DRAW
? ei.mi.scale_factor_WHITE(pos)
: ei.mi.scale_factor_BLACK(pos);
// 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.gamePhase < PhaseC.PHASE_MIDGAME
&& (pos.pieceCount[ColorC.WHITE][PieceTypeC.BISHOP] == 1
&& pos.pieceCount[ColorC.BLACK][PieceTypeC.BISHOP] == 1
&& (((((pos.pieceList[ColorC.WHITE][PieceTypeC.BISHOP][0]
^ pos.pieceList[ColorC.BLACK][PieceTypeC.BISHOP][0]) >> 3)
^ (pos.pieceList[ColorC.WHITE][PieceTypeC.BISHOP][0]
^ pos.pieceList[ColorC.BLACK][PieceTypeC.BISHOP][0])) & 1) != 0))
&& sf == ScaleFactorC.SCALE_FACTOR_NORMAL)
{
// Only the two bishops ?
if (pos.st.npMaterialWHITE == Constants.BishopValueMidgame
&& pos.st.npMaterialBLACK == Constants.BishopValueMidgame)
{
// Check for KBP vs KB with only a single pawn that is almost
// certainly a draw or at least two pawns.
sf = (pos.pieceCount[ColorC.WHITE][PieceTypeC.PAWN] + pos.pieceCount[ColorC.BLACK][PieceTypeC.PAWN]
== 1)
? (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);
}
}
// Interpolate between the middle game and the endgame score
margin = pos.sideToMove == ColorC.WHITE ? marginsWHITE : marginsBLACK;
// interpolate
//Value v = interpolate(score, ei.mi.game_phase(), sf);
var ev = (((short)(score & 0xffff)) * sf) / ScaleFactorC.SCALE_FACTOR_NORMAL;
var result = ((((score + 32768) & ~0xffff) / 0x10000) * ei.mi.gamePhase + ev * (128 - ei.mi.gamePhase)) / 128;
var v = ((result + GrainSize / 2) & ~(GrainSize - 1));
// In case of tracing add all single evaluation contributions for both white and black
if (Trace)
{
trace_add(TracedTypeC.PST, pos.psq_score());
trace_add(TracedTypeC.IMBALANCE, ei.mi.material_value());
trace_add(PieceTypeC.PAWN, ei.pi.pawns_value());
trace_add(
TracedTypeC.MOBILITY,
Utils.apply_weight(mobilityWhite, Weights[EvalWeightC.Mobility]),
Utils.apply_weight(mobilityBlack, Weights[EvalWeightC.Mobility]));
trace_add(
TracedTypeC.THREAT,
evaluate_threats(ColorC.WHITE, pos, ei),
evaluate_threats(ColorC.BLACK, pos, ei));
trace_add(
TracedTypeC.PASSED,
evaluate_passed_pawns(ColorC.WHITE, pos, ei),
evaluate_passed_pawns(ColorC.BLACK, pos, ei));
trace_add(TracedTypeC.UNSTOPPABLE, evaluate_unstoppable_pawns(pos, ei));
var w = Utils.make_score(ei.mi.space_weight() * evaluate_space(ColorC.WHITE, pos, ei), 0);
var b = Utils.make_score(ei.mi.space_weight() * evaluate_space(ColorC.BLACK, pos, ei), 0);
trace_add(
TracedTypeC.SPACE,
Utils.apply_weight(w, Weights[EvalWeightC.Space]),
Utils.apply_weight(b, Weights[EvalWeightC.Space]));
trace_add(TracedTypeC.TOTAL, score);
TraceStream.Append("\nUncertainty margin: White: ");
TraceStream.Append(FormatDouble(to_cp(marginsWHITE), null, true));
TraceStream.Append(", Black: ");
TraceStream.Append(FormatDouble(to_cp(marginsBLACK), null, true));
TraceStream.Append("\nScaling: ");
TraceStream.Append(FormatDouble((100.0 * ei.mi.game_phase() / 128.0), 6, false));
TraceStream.Append("% MG, ");
TraceStream.Append(FormatDouble((100.0 * (1.0 - ei.mi.game_phase() / 128.0)), 6, false));
TraceStream.Append("% * ");
TraceStream.Append(FormatDouble(((100.0 * sf) / ScaleFactorC.SCALE_FACTOR_NORMAL), 6, false));
TraceStream.Append("% EG.\n");
TraceStream.Append("Total evaluation: ");
TraceStream.Append(FormatDouble(to_cp(v), null, false));
}
ei.pi = null;
ei.mi = null;
EvalInfoBroker.Free();
return pos.sideToMove == ColorC.WHITE ? v : -v;
}
