/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
const Value MidgameLimit = Value(15581);
const Value EndgameLimit = Value(3998);
- // Scale factors used when one side has no more pawns
- const int NoPawnsSF[4] = { 6, 12, 32 };
-
// Polynomial material balance parameters
- const Value RedundantQueen = Value(320);
- const Value RedundantRook = Value(554);
// pair pawn knight bishop rook queen
- const int LinearCoefficients[6] = { 1617, -162, -1172, -190, 105, 26 };
+ const int LinearCoefficients[6] = { 1852, -162, -1122, -183, 249, -154 };
const int QuadraticCoefficientsSameColor[][PIECE_TYPE_NB] = {
// pair pawn knight bishop rook queen
- { 7 }, // Bishop pair
+ { 0 }, // Bishop pair
{ 39, 2 }, // Pawn
{ 35, 271, -4 }, // Knight
- { 7, 105, 4, 7 }, // Bishop
- { -27, -2, 46, 100, 56 }, // Rook
- { 58, 29, 83, 148, -3, -25 } // Queen
+ { 0, 105, 4, 0 }, // Bishop
+ { -27, -2, 46, 100, -141 }, // Rook
+ {-177, 25, 129, 142, -137, 0 } // Queen
};
const int QuadraticCoefficientsOppositeColor[][PIECE_TYPE_NB] = {
// THEIR PIECES
// pair pawn knight bishop rook queen
- { 41 }, // Bishop pair
- { 37, 41 }, // Pawn
- { 10, 62, 41 }, // Knight OUR PIECES
- { 57, 64, 39, 41 }, // Bishop
- { 50, 40, 23, -22, 41 }, // Rook
- { 106, 101, 3, 151, 171, 41 } // Queen
+ { 0 }, // Bishop pair
+ { 37, 0 }, // Pawn
+ { 10, 62, 0 }, // Knight OUR PIECES
+ { 57, 64, 39, 0 }, // Bishop
+ { 50, 40, 23, -22, 0 }, // Rook
+ { 98, 105, -39, 141, 274, 0 } // Queen
};
- // Endgame evaluation and scaling functions accessed direcly and not through
- // the function maps because correspond to more then one material hash key.
- Endgame<KmmKm> EvaluateKmmKm[] = { Endgame<KmmKm>(WHITE), Endgame<KmmKm>(BLACK) };
+ // Endgame evaluation and scaling functions are accessed directly and not through
+ // the function maps because they correspond to more than one material hash key.
Endgame<KXK> EvaluateKXK[] = { Endgame<KXK>(WHITE), Endgame<KXK>(BLACK) };
Endgame<KBPsK> ScaleKBPsK[] = { Endgame<KBPsK>(WHITE), Endgame<KBPsK>(BLACK) };
&& pos.count<PAWN>(Them) >= 1;
}
- /// imbalance() calculates imbalance comparing piece count of each
+ /// imbalance() calculates the imbalance by comparing the piece count of each
/// piece type for both colors.
template<Color Us>
int pt1, pt2, pc, v;
int value = 0;
- // Redundancy of major pieces, formula based on Kaufman's paper
- // "The Evaluation of Material Imbalances in Chess"
- if (pieceCount[Us][ROOK] > 0)
- value -= RedundantRook * (pieceCount[Us][ROOK] - 1)
- + RedundantQueen * pieceCount[Us][QUEEN];
-
// Second-degree polynomial material imbalance by Tord Romstad
- for (pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; pt1++)
+ for (pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; ++pt1)
{
pc = pieceCount[Us][pt1];
if (!pc)
v = LinearCoefficients[pt1];
- for (pt2 = NO_PIECE_TYPE; pt2 <= pt1; pt2++)
+ for (pt2 = NO_PIECE_TYPE; pt2 <= pt1; ++pt2)
v += QuadraticCoefficientsSameColor[pt1][pt2] * pieceCount[Us][pt2]
+ QuadraticCoefficientsOppositeColor[pt1][pt2] * pieceCount[Them][pt2];
value += pc * v;
}
+
return value;
}
e->factor[WHITE] = e->factor[BLACK] = (uint8_t)SCALE_FACTOR_NORMAL;
e->gamePhase = game_phase(pos);
- // Let's look if we have a specialized evaluation function for this
- // particular material configuration. First we look for a fixed
- // configuration one, then a generic one if previous search failed.
+ // Let's look if we have a specialized evaluation function for this particular
+ // material configuration. Firstly we look for a fixed configuration one, then
+ // for a generic one if the previous search failed.
if (endgames.probe(key, e->evaluationFunction))
return e;
return e;
}
- if (!pos.pieces(PAWN) && !pos.pieces(ROOK) && !pos.pieces(QUEEN))
- {
- // Minor piece endgame with at least one minor piece per side and
- // no pawns. Note that the case KmmK is already handled by KXK.
- assert((pos.pieces(WHITE, KNIGHT) | pos.pieces(WHITE, BISHOP)));
- assert((pos.pieces(BLACK, KNIGHT) | pos.pieces(BLACK, BISHOP)));
-
- if ( pos.count<BISHOP>(WHITE) + pos.count<KNIGHT>(WHITE) <= 2
- && pos.count<BISHOP>(BLACK) + pos.count<KNIGHT>(BLACK) <= 2)
- {
- e->evaluationFunction = &EvaluateKmmKm[pos.side_to_move()];
- return e;
- }
- }
-
// OK, we didn't find any special evaluation function for the current
// material configuration. Is there a suitable scaling function?
//
return e;
}
- // Generic scaling functions that refer to more then one material
- // distribution. Should be probed after the specialized ones.
+ // Generic scaling functions that refer to more than one material
+ // distribution. They should be probed after the specialized ones.
// Note that these ones don't return after setting the function.
if (is_KBPsKs<WHITE>(pos))
e->scalingFunction[WHITE] = &ScaleKBPsK[WHITE];
Value npm_w = pos.non_pawn_material(WHITE);
Value npm_b = pos.non_pawn_material(BLACK);
- if (npm_w + npm_b == VALUE_ZERO)
+ if (npm_w + npm_b == VALUE_ZERO && pos.pieces(PAWN))
{
if (!pos.count<PAWN>(BLACK))
{
}
}
- // No pawns makes it difficult to win, even with a material advantage
+ // No pawns makes it difficult to win, even with a material advantage. This
+ // catches some trivial draws like KK, KBK and KNK and gives a very drawish
+ // scale factor for cases such as KRKBP and KmmKm (except for KBBKN).
if (!pos.count<PAWN>(WHITE) && npm_w - npm_b <= BishopValueMg)
- {
- e->factor[WHITE] = (uint8_t)
- (npm_w == npm_b || npm_w < RookValueMg ? 0 : NoPawnsSF[std::min(pos.count<BISHOP>(WHITE), 2)]);
- }
+ e->factor[WHITE] = uint8_t(npm_w < RookValueMg ? SCALE_FACTOR_DRAW : npm_b <= BishopValueMg ? 4 : 12);
if (!pos.count<PAWN>(BLACK) && npm_b - npm_w <= BishopValueMg)
- {
- e->factor[BLACK] = (uint8_t)
- (npm_w == npm_b || npm_b < RookValueMg ? 0 : NoPawnsSF[std::min(pos.count<BISHOP>(BLACK), 2)]);
- }
+ e->factor[BLACK] = uint8_t(npm_b < RookValueMg ? SCALE_FACTOR_DRAW : npm_w <= BishopValueMg ? 4 : 12);
+
+ if (pos.count<PAWN>(WHITE) == 1 && npm_w - npm_b <= BishopValueMg)
+ e->factor[WHITE] = (uint8_t) SCALE_FACTOR_ONEPAWN;
+
+ if (pos.count<PAWN>(BLACK) == 1 && npm_b - npm_w <= BishopValueMg)
+ e->factor[BLACK] = (uint8_t) SCALE_FACTOR_ONEPAWN;
// Compute the space weight
if (npm_w + npm_b >= 2 * QueenValueMg + 4 * RookValueMg + 2 * KnightValueMg)
}
// Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
- // for the bishop pair "extended piece", this allow us to be more flexible
+ // for the bishop pair "extended piece", which allows us to be more flexible
// in defining bishop pair bonuses.
const int pieceCount[COLOR_NB][PIECE_TYPE_NB] = {
{ pos.count<BISHOP>(WHITE) > 1, pos.count<PAWN>(WHITE), pos.count<KNIGHT>(WHITE),
projects / stockfish / blobdiff