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96 pmbaty 1
/*
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  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
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  Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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  Stockfish is free software: you can redistribute it and/or modify
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  it under the terms of the GNU General Public License as published by
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  the Free Software Foundation, either version 3 of the License, or
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  (at your option) any later version.
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  Stockfish is distributed in the hope that it will be useful,
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  but WITHOUT ANY WARRANTY; without even the implied warranty of
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  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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  GNU General Public License for more details.
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  You should have received a copy of the GNU General Public License
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  along with this program.  If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <algorithm> // For std::min
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#include <cassert>
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#include <cstring>   // For std::memset
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#include "material.h"
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#include "thread.h"
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using namespace std;
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namespace {
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  // Polynomial material imbalance parameters
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  const int QuadraticOurs[][PIECE_TYPE_NB] = {
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    //            OUR PIECES
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    // pair pawn knight bishop rook queen
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    {1667                               }, // Bishop pair
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    {  40,    2                         }, // Pawn
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    {  32,  255,  -3                    }, // Knight      OUR PIECES
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    {   0,  104,   4,    0              }, // Bishop
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    { -26,   -2,  47,   105,  -149      }, // Rook
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    {-185,   24, 122,   137,  -134,   0 }  // Queen
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  };
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  const int QuadraticTheirs[][PIECE_TYPE_NB] = {
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    //           THEIR PIECES
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    // pair pawn knight bishop rook queen
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    {   0                               }, // Bishop pair
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    {  36,    0                         }, // Pawn
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    {   9,   63,   0                    }, // Knight      OUR PIECES
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    {  59,   65,  42,     0             }, // Bishop
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    {  46,   39,  24,   -24,    0       }, // Rook
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    { 101,  100, -37,   141,  268,    0 }  // Queen
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  };
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  // Endgame evaluation and scaling functions are accessed directly and not through
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  // the function maps because they correspond to more than one material hash key.
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  Endgame<KXK>    EvaluateKXK[] = { Endgame<KXK>(WHITE),    Endgame<KXK>(BLACK) };
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  Endgame<KBPsK>  ScaleKBPsK[]  = { Endgame<KBPsK>(WHITE),  Endgame<KBPsK>(BLACK) };
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  Endgame<KQKRPs> ScaleKQKRPs[] = { Endgame<KQKRPs>(WHITE), Endgame<KQKRPs>(BLACK) };
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  Endgame<KPsK>   ScaleKPsK[]   = { Endgame<KPsK>(WHITE),   Endgame<KPsK>(BLACK) };
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  Endgame<KPKP>   ScaleKPKP[]   = { Endgame<KPKP>(WHITE),   Endgame<KPKP>(BLACK) };
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  // Helper used to detect a given material distribution
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  bool is_KXK(const Position& pos, Color us) {
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    return  !more_than_one(pos.pieces(~us))
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          && pos.non_pawn_material(us) >= RookValueMg;
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  }
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  bool is_KBPsKs(const Position& pos, Color us) {
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    return   pos.non_pawn_material(us) == BishopValueMg
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          && pos.count<BISHOP>(us) == 1
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          && pos.count<PAWN  >(us) >= 1;
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  }
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  bool is_KQKRPs(const Position& pos, Color us) {
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    return  !pos.count<PAWN>(us)
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          && pos.non_pawn_material(us) == QueenValueMg
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          && pos.count<QUEEN>(us)  == 1
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          && pos.count<ROOK>(~us) == 1
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          && pos.count<PAWN>(~us) >= 1;
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  }
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  /// imbalance() calculates the imbalance by comparing the piece count of each
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  /// piece type for both colors.
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  template<Color Us>
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  int imbalance(const int pieceCount[][PIECE_TYPE_NB]) {
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    const Color Them = (Us == WHITE ? BLACK : WHITE);
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    int bonus = 0;
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    // Second-degree polynomial material imbalance by Tord Romstad
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    for (int pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; ++pt1)
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    {
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        if (!pieceCount[Us][pt1])
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            continue;
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        int v = 0;
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        for (int pt2 = NO_PIECE_TYPE; pt2 <= pt1; ++pt2)
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            v +=  QuadraticOurs[pt1][pt2] * pieceCount[Us][pt2]
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                + QuadraticTheirs[pt1][pt2] * pieceCount[Them][pt2];
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        bonus += pieceCount[Us][pt1] * v;
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    }
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    return bonus;
110
  }
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} // namespace
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namespace Material {
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/// Material::probe() looks up the current position's material configuration in
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/// the material hash table. It returns a pointer to the Entry if the position
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/// is found. Otherwise a new Entry is computed and stored there, so we don't
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/// have to recompute all when the same material configuration occurs again.
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Entry* probe(const Position& pos) {
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123
  Key key = pos.material_key();
124
  Entry* e = pos.this_thread()->materialTable[key];
125
 
126
  if (e->key == key)
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      return e;
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129
  std::memset(e, 0, sizeof(Entry));
130
  e->key = key;
131
  e->factor[WHITE] = e->factor[BLACK] = (uint8_t)SCALE_FACTOR_NORMAL;
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  e->gamePhase = pos.game_phase();
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134
  // Let's look if we have a specialized evaluation function for this particular
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  // material configuration. Firstly we look for a fixed configuration one, then
136
  // for a generic one if the previous search failed.
137
  if ((e->evaluationFunction = pos.this_thread()->endgames.probe<Value>(key)) != nullptr)
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      return e;
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140
  for (Color c = WHITE; c <= BLACK; ++c)
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      if (is_KXK(pos, c))
142
      {
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          e->evaluationFunction = &EvaluateKXK[c];
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          return e;
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      }
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147
  // OK, we didn't find any special evaluation function for the current material
148
  // configuration. Is there a suitable specialized scaling function?
149
  EndgameBase<ScaleFactor>* sf;
150
 
151
  if ((sf = pos.this_thread()->endgames.probe<ScaleFactor>(key)) != nullptr)
152
  {
153
      e->scalingFunction[sf->strong_side()] = sf; // Only strong color assigned
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      return e;
155
  }
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157
  // We didn't find any specialized scaling function, so fall back on generic
158
  // ones that refer to more than one material distribution. Note that in this
159
  // case we don't return after setting the function.
160
  for (Color c = WHITE; c <= BLACK; ++c)
161
  {
162
    if (is_KBPsKs(pos, c))
163
        e->scalingFunction[c] = &ScaleKBPsK[c];
164
 
165
    else if (is_KQKRPs(pos, c))
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        e->scalingFunction[c] = &ScaleKQKRPs[c];
167
  }
168
 
169
  Value npm_w = pos.non_pawn_material(WHITE);
170
  Value npm_b = pos.non_pawn_material(BLACK);
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172
  if (npm_w + npm_b == VALUE_ZERO && pos.pieces(PAWN)) // Only pawns on the board
173
  {
174
      if (!pos.count<PAWN>(BLACK))
175
      {
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          assert(pos.count<PAWN>(WHITE) >= 2);
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178
          e->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
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      }
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      else if (!pos.count<PAWN>(WHITE))
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      {
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          assert(pos.count<PAWN>(BLACK) >= 2);
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184
          e->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
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      }
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      else if (pos.count<PAWN>(WHITE) == 1 && pos.count<PAWN>(BLACK) == 1)
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      {
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          // This is a special case because we set scaling functions
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          // for both colors instead of only one.
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          e->scalingFunction[WHITE] = &ScaleKPKP[WHITE];
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          e->scalingFunction[BLACK] = &ScaleKPKP[BLACK];
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      }
193
  }
194
 
195
  // Zero or just one pawn makes it difficult to win, even with a small material
196
  // advantage. This catches some trivial draws like KK, KBK and KNK and gives a
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  // drawish scale factor for cases such as KRKBP and KmmKm (except for KBBKN).
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  if (!pos.count<PAWN>(WHITE) && npm_w - npm_b <= BishopValueMg)
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      e->factor[WHITE] = uint8_t(npm_w <  RookValueMg   ? SCALE_FACTOR_DRAW :
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                                 npm_b <= BishopValueMg ? 4 : 14);
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202
  if (!pos.count<PAWN>(BLACK) && npm_b - npm_w <= BishopValueMg)
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      e->factor[BLACK] = uint8_t(npm_b <  RookValueMg   ? SCALE_FACTOR_DRAW :
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                                 npm_w <= BishopValueMg ? 4 : 14);
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206
  if (pos.count<PAWN>(WHITE) == 1 && npm_w - npm_b <= BishopValueMg)
207
      e->factor[WHITE] = (uint8_t) SCALE_FACTOR_ONEPAWN;
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209
  if (pos.count<PAWN>(BLACK) == 1 && npm_b - npm_w <= BishopValueMg)
210
      e->factor[BLACK] = (uint8_t) SCALE_FACTOR_ONEPAWN;
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212
  // Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
213
  // for the bishop pair "extended piece", which allows us to be more flexible
214
  // in defining bishop pair bonuses.
215
  const int PieceCount[COLOR_NB][PIECE_TYPE_NB] = {
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  { pos.count<BISHOP>(WHITE) > 1, pos.count<PAWN>(WHITE), pos.count<KNIGHT>(WHITE),
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    pos.count<BISHOP>(WHITE)    , pos.count<ROOK>(WHITE), pos.count<QUEEN >(WHITE) },
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  { pos.count<BISHOP>(BLACK) > 1, pos.count<PAWN>(BLACK), pos.count<KNIGHT>(BLACK),
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    pos.count<BISHOP>(BLACK)    , pos.count<ROOK>(BLACK), pos.count<QUEEN >(BLACK) } };
220
 
221
  e->value = int16_t((imbalance<WHITE>(PieceCount) - imbalance<BLACK>(PieceCount)) / 16);
222
  return e;
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}
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} // namespace Material