Stockfish 1.2

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/benchmark.cpp

@@ -71,8 +71,8 @@ void benchmark(const std::string& commandLine) {
 
   std::istringstream csVal(commandLine);
   std::istringstream csStr(commandLine);
-  std::string ttSize, threads, fileName;
-  int val, secsPerPos;
+  std::string ttSize, threads, fileName, limitType;
+  int val, secsPerPos, maxDepth, maxNodes;
 
   csStr >> ttSize;
   csVal >> val;
@@ -95,8 +95,18 @@ void benchmark(const std::string& commandLine) {
   set_option_value("Use Search Log", "true");
   set_option_value("Search Log Filename", "bench.txt");
 
-  csVal >> secsPerPos;
+  csVal >> val;
   csVal >> fileName;
+  csVal >> limitType;
+
+  secsPerPos = maxDepth = maxNodes = 0;
+
+  if (limitType == "time")
+      secsPerPos = val * 1000;
+  else if (limitType == "depth")
+      maxDepth = val;
+  else
+      maxNodes = val;
 
   std::vector<std::string> positions;
   
@@ -121,12 +131,21 @@ void benchmark(const std::string& commandLine) {
       for (int i = 0; i < 16; i++)
           positions.push_back(std::string(BenchmarkPositions[i]));
 
+  int startTime = get_system_time();
   std::vector<std::string>::iterator it;
-  for (it = positions.begin(); it != positions.end(); ++it)
+  int cnt = 1;
+  int64_t totalNodes = 0;
+  for (it = positions.begin(); it != positions.end(); ++it, ++cnt)
   {
-      Move moves[1] = {MOVE_NONE};
-      int dummy[2] = {0, 0};
+      Move moves[1] = {MOVE_NONE};
+      int dummy[2] = {0, 0};
       Position pos(*it);
-      think(pos, true, false, 0, dummy, dummy, 0, 0, 0, secsPerPos * 1000, moves);
+      std::cout << "\nProcessing position " << cnt << '/' << positions.size() << std::endl << std::endl;
+      think(pos, true, false, 0, dummy, dummy, 0, maxDepth, maxNodes, secsPerPos, moves);
+      totalNodes += nodes_searched();
   }
+  std::cout << "\nProcessing time (ms) " << get_system_time() - startTime << std::endl
+            << "Nodes searched " << totalNodes << std::endl
+            << "Press any key to exit" << std::endl;
+  std::cin >> fileName;
 }

src/bitboard.cpp

@@ -250,8 +250,8 @@ Bitboard BMask[64];
 int BAttackIndex[64];
 Bitboard BAttacks[0x1480];
 
-Bitboard SetMaskBB[64];
-Bitboard ClearMaskBB[64];
+Bitboard SetMaskBB[65];
+Bitboard ClearMaskBB[65];
 
 Bitboard StepAttackBB[16][64];
 Bitboard RayBB[64][8];
@@ -433,6 +433,8 @@ namespace {
   // be necessary to touch any of them.
 
   void init_masks() {
+    SetMaskBB[SQ_NONE] = 0ULL;
+    ClearMaskBB[SQ_NONE] = ~SetMaskBB[SQ_NONE];
     for(Square s = SQ_A1; s <= SQ_H8; s++) {
       SetMaskBB[s] = (1ULL << s);
       ClearMaskBB[s] = ~SetMaskBB[s];

src/bitboard.h

@@ -113,8 +113,8 @@ extern const Bitboard RankBB[8];
 extern const Bitboard RelativeRankBB[2][8];
 extern const Bitboard InFrontBB[2][8];
 
-extern Bitboard SetMaskBB[64];
-extern Bitboard ClearMaskBB[64];
+extern Bitboard SetMaskBB[65];
+extern Bitboard ClearMaskBB[65];
 
 extern Bitboard StepAttackBB[16][64];
 extern Bitboard RayBB[64][8];
@@ -236,6 +236,19 @@ inline Bitboard in_front_bb(Color c, Square s) {
 }
 
 
+/// behind_bb() takes a color and a rank or square as input, and returns a
+/// bitboard representing all the squares on all ranks behind of the rank
+/// (or square), from the given color's point of view.
+
+inline Bitboard behind_bb(Color c, Rank r) {
+  return InFrontBB[opposite_color(c)][r];
+}
+
+inline Bitboard behind_bb(Color c, Square s) {
+  return in_front_bb(opposite_color(c), square_rank(s));
+}
+
+
 /// ray_bb() gives a bitboard representing all squares along the ray in a
 /// given direction from a given square.
 

src/endgame.cpp

@@ -62,6 +62,13 @@ KRKNEvaluationFunction EvaluateKNKR = KRKNEvaluationFunction(BLACK);
 KQKREvaluationFunction EvaluateKQKR = KQKREvaluationFunction(WHITE);
 KQKREvaluationFunction EvaluateKRKQ = KQKREvaluationFunction(BLACK);
 
+// KBB vs KN:
+KBBKNEvaluationFunction EvaluateKBBKN = KBBKNEvaluationFunction(WHITE);
+KBBKNEvaluationFunction EvaluateKNKBB = KBBKNEvaluationFunction(BLACK);
+
+// K and two minors vs K and one or two minors:
+KmmKmEvaluationFunction EvaluateKmmKm = KmmKmEvaluationFunction(WHITE);
+
 
 /// Scaling functions
 
@@ -187,6 +194,8 @@ KRKPEvaluationFunction::KRKPEvaluationFunction(Color c) : EndgameEvaluationFunct
 KRKBEvaluationFunction::KRKBEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
 KRKNEvaluationFunction::KRKNEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
 KQKREvaluationFunction::KQKREvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
+KBBKNEvaluationFunction::KBBKNEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
+KmmKmEvaluationFunction::KmmKmEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
 
 
 ScalingFunction::ScalingFunction(Color c) {
@@ -420,6 +429,36 @@ Value KQKREvaluationFunction::apply(const Position &pos) {
 }
 
 
+Value KBBKNEvaluationFunction::apply(const Position &pos) {
+  assert(pos.piece_count(strongerSide, BISHOP) == 2);
+  assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame);
+  assert(pos.piece_count(weakerSide, KNIGHT) == 1);
+  assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
+  assert(pos.pawns() == EmptyBoardBB);
+
+  Value result = BishopValueEndgame;
+  Square wksq = pos.king_square(strongerSide);
+  Square bksq = pos.king_square(weakerSide);
+  Square nsq = pos.piece_list(weakerSide, KNIGHT, 0);
+
+  // Bonus for attacking king close to defending king
+  result += distance_bonus(square_distance(wksq, bksq));
+
+  // Bonus for driving the defending king and knight apart
+  result += Value(square_distance(bksq, nsq) * 32);
+
+  // Bonus for restricting the knight's mobility
+  result += Value((8 - count_1s_max_15(pos.piece_attacks<KNIGHT>(nsq))) * 8);
+
+  return (strongerSide == pos.side_to_move())? result : -result;
+}
+
+
+Value KmmKmEvaluationFunction::apply(const Position &pos) {
+  return Value(0);
+}
+
+
 /// KBPKScalingFunction scales endgames where the stronger side has king,
 /// bishop and one or more pawns.  It checks for draws with rook pawns and a
 /// bishop of the wrong color.  If such a draw is detected, ScaleFactor(0) is
@@ -604,6 +643,16 @@ ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
                   - (8 * square_distance(wpsq, queeningSq) +
                      2 * square_distance(wksq, queeningSq)));
 
+  // If the pawn is not far advanced, and the defending king is somewhere in
+  // the pawn's path, it's probably a draw:
+  if(r <= RANK_4 && bksq > wpsq) {
+    if(square_file(bksq) == square_file(wpsq))
+      return ScaleFactor(10);
+    if(abs(square_file(bksq) - square_file(wpsq)) == 1
+       && square_distance(wksq, bksq) > 2)
+      return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
+  }
+
   return SCALE_FACTOR_NONE;
 }
 

src/endgame.h

@@ -99,6 +99,20 @@ public:
   Value apply(const Position &pos);
 };
 
+// KBB vs KN:
+class KBBKNEvaluationFunction : public EndgameEvaluationFunction {
+public:
+  KBBKNEvaluationFunction(Color C);
+  Value apply(const Position &pos);
+};
+
+// K and two minors vs K and one or two minors:
+class KmmKmEvaluationFunction : public EndgameEvaluationFunction {
+public:
+  KmmKmEvaluationFunction(Color c);
+  Value apply(const Position &pos);
+};
+
 
 /// Abstract base class for all evaluation scaling functions:
 
@@ -205,6 +219,12 @@ extern KRKNEvaluationFunction EvaluateKRKN, EvaluateKNKR;
 // KQ vs KR:
 extern KQKREvaluationFunction EvaluateKQKR, EvaluateKRKQ;
 
+// KBB vs KN:
+extern KBBKNEvaluationFunction EvaluateKBBKN, EvaluateKNKBB;
+
+// K and two minors vs K and one or two minors:
+extern KmmKmEvaluationFunction EvaluateKmmKm;
+
 // KBP vs K:
 extern KBPKScalingFunction ScaleKBPK, ScaleKKBP;
 

src/evaluate.cpp

@@ -52,6 +52,7 @@ namespace {
   int WeightPassedPawnsMidgame   = 0x100;
   int WeightPassedPawnsEndgame   = 0x100;
   int WeightKingSafety[2] = { 0x100, 0x100 };
+  int WeightSpace;
 
   // Internal evaluation weights.  These are applied on top of the evaluation
   // weights read from UCI parameters.  The purpose is to be able to change
@@ -63,8 +64,9 @@ namespace {
   const int WeightPawnStructureEndgameInternal = 0x100;
   const int WeightPassedPawnsMidgameInternal   = 0x100;
   const int WeightPassedPawnsEndgameInternal   = 0x100;
-  const int WeightKingSafetyInternal           = 0x100;
-  const int WeightKingOppSafetyInternal        = 0x100;
+  const int WeightKingSafetyInternal           = 0x110;
+  const int WeightKingOppSafetyInternal        = 0x110;
+  const int WeightSpaceInternal                = 0x30;
 
   // Visually better to define tables constants
   typedef Value V;
@@ -203,6 +205,19 @@ namespace {
     ((1ULL << SQ_A8) | (1ULL << SQ_H8))
   };
 
+  // The SpaceMask[color] contains area of the board which is consdered by
+  // the space evaluation.  In the middle game, each side is given a bonus
+  // based on how many squares inside this area are safe and available for
+  // friendly minor pieces.
+  const Bitboard SpaceMask[2] = {
+    (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
+    (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
+    (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
+    (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
+    (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
+    (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
+  };
+
   /// King safety constants and variables.  The king safety scores are taken
   /// from the array SafetyTable[].  Various little "meta-bonuses" measuring
   /// the strength of the attack are added up into an integer, which is used
@@ -215,8 +230,7 @@ namespace {
   const int KnightAttackWeight = 2;
 
   // Bonuses for safe checks for each piece type.
-  int QueenContactCheckBonus = 4;
-  int RookContactCheckBonus  = 2;
+  int QueenContactCheckBonus = 3;
   int QueenCheckBonus        = 2;
   int RookCheckBonus         = 1;
   int BishopCheckBonus       = 1;
@@ -246,18 +260,18 @@ namespace {
   // in init_safety().
   Value SafetyTable[100];
 
-  // Pawn and material hash tables, indexed by the current thread id:
+  // Pawn and material hash tables, indexed by the current thread id
   PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
   MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
 
-  // Sizes of pawn and material hash tables:
+  // Sizes of pawn and material hash tables
   const int PawnTableSize = 16384;
   const int MaterialTableSize = 1024;
 
   // Array which gives the number of nonzero bits in an 8-bit integer:
   uint8_t BitCount8Bit[256];
 
-  // Function prototypes:
+  // Function prototypes
   void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei);
   void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei);
   void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei);
@@ -270,6 +284,7 @@ namespace {
   void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
                                     EvalInfo &ei);
 
+  void evaluate_space(const Position &p, Color us, EvalInfo &ei);
   inline Value apply_weight(Value v, int w);
   Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
 
@@ -407,6 +422,13 @@ Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
 
         ei.mgValue += ei.pi->kingside_storm_value(WHITE)
                     - ei.pi->queenside_storm_value(BLACK);
+
+    // Evaluate space for both sides
+    if (ei.mi->space_weight() > 0)
+    {
+        evaluate_space(pos, WHITE, ei);
+        evaluate_space(pos, BLACK, ei);
+    }
   }
 
   // Mobility
@@ -414,7 +436,7 @@ Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
   ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
 
   // If we don't already have an unusual scale factor, check for opposite
-  // colored bishop endgames, and use a lower scale for those:
+  // colored bishop endgames, and use a lower scale for those
   if (   phase < PHASE_MIDGAME
       && pos.opposite_colored_bishops()
       && (   (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
@@ -527,6 +549,7 @@ void read_weights(Color us) {
 
   WeightKingSafety[us]   = weight_option("Cowardice", WeightKingSafetyInternal);
   WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
+  WeightSpace = weight_option("Space", WeightSpaceInternal);
 
   init_safety();
 }
@@ -613,7 +636,6 @@ namespace {
 
   void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
 
-    //Bitboard b = p.rook_attacks(s);
     Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
     ei.attackedBy[us][ROOK] |= b;
 
@@ -744,14 +766,14 @@ namespace {
       Bitboard occ = p.occupied_squares(), b, b2;
 
       // Initialize the 'attackUnits' variable, which is used later on as an
-      // index to the SafetyTable[] array.  The initial is based on the number
-      // and types of the attacking pieces, the number of attacked and
+      // index to the SafetyTable[] array.  The initial value is based on the
+      // number and types of the attacking pieces, the number of attacked and
       // undefended squares around the king, the square of the king, and the
       // quality of the pawn shelter.
       int attackUnits =
             Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
           + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
-          + InitKingDanger[relative_square(us, s)] - shelter / 32;
+          + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
 
       // Analyse safe queen contact checks
       b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
@@ -797,25 +819,8 @@ namespace {
           }
         }
       }
-      // Analyse safe rook contact checks:
-      if (RookContactCheckBonus)
-      {
-          b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
-          if (b)
-          {
-              Bitboard attackedByOthers =
-                    ei.attacked_by(them, PAWN)   | ei.attacked_by(them, KNIGHT)
-                  | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
 
-              b &= attackedByOthers;
-              if (b)
-              {
-                  int count = count_1s_max_15(b);
-                  attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
-              }
-          }
-      }
-      // Analyse safe distance checks:
+      // Analyse safe distance checks
       if (QueenCheckBonus > 0 || RookCheckBonus > 0)
       {
           b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
@@ -931,6 +936,13 @@ namespace {
           b2 = squares_in_front_of(us, s);
           b3 = b2 & ei.attacked_by(them);
           b4 = b2 & ei.attacked_by(us);
+
+          // If there is an enemy rook or queen attacking the pawn from behind,
+          // add all X-ray attacks by the rook or queen.
+          if(bit_is_set(ei.attacked_by(them,ROOK)|ei.attacked_by(them,QUEEN),s)
+             && squares_behind(us, s) & pos.rooks_and_queens(them))
+            b3 = b2;
+
           if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
             // There are no enemy pieces in the pawn's path!  Are any of the
             // squares in the pawn's path attacked by the enemy?
@@ -1101,14 +1113,54 @@ namespace {
   }
 
 
-  // apply_weight applies an evaluation weight to a value.
+  // evaluate_space() computes the space evaluation for a given side. The
+  // space evaluation is a simple bonus based on the number of safe squares
+  // available for minor pieces on the central four files on ranks 2--4. Safe
+  // squares one, two or three squares behind a friendly pawn are counted
+  // twice. Finally, the space bonus is scaled by a weight taken from the
+  // material hash table.
+
+  void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
+
+    Color them = opposite_color(us);
+
+    // Find the safe squares for our pieces inside the area defined by
+    // SpaceMask[us].  A square is unsafe it is attacked by an enemy
+    // pawn, or if it is undefended and attacked by an enemy piece.
+
+    Bitboard safeSquares =
+      SpaceMask[us] & ~pos.pawns(us) & ~ei.attacked_by(them, PAWN)
+      & ~(~ei.attacked_by(us) & ei.attacked_by(them));
+
+    // Find all squares which are at most three squares behind some friendly
+    // pawn.
+    Bitboard behindFriendlyPawns = pos.pawns(us);
+    if(us == WHITE) {
+      behindFriendlyPawns |= (behindFriendlyPawns >> 8);
+      behindFriendlyPawns |= (behindFriendlyPawns >> 16);
+    }
+    else {
+      behindFriendlyPawns |= (behindFriendlyPawns << 8);
+      behindFriendlyPawns |= (behindFriendlyPawns << 16);
+    }
+
+    int space =
+      count_1s_max_15(safeSquares)
+      + count_1s_max_15(behindFriendlyPawns & safeSquares);
+
+    ei.mgValue += Sign[us] *
+      apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
+  }
+
+
+  // apply_weight() applies an evaluation weight to a value
 
   inline Value apply_weight(Value v, int w) {
     return (v*w) / 0x100;
   }
 
 
-  // scale_by_game_phase interpolates between a middle game and an endgame
+  // scale_by_game_phase() interpolates between a middle game and an endgame
   // score, based on game phase.  It also scales the return value by a
   // ScaleFactor array.
 
@@ -1120,13 +1172,7 @@ namespace {
 
     ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
 
-    // Linearized sigmoid interpolator
-    int sph = int(ph);
-    sph -= (64 - sph) / 4;
-    sph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sph));
-
-    Value result = Value(int((mv * sph + ev * (128 - sph)) / 128));
-
+    Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
     return Value(int(result) & ~(GrainSize - 1));
   }
 
@@ -1162,7 +1208,6 @@ namespace {
   void init_safety() {
 
     QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
-    RookContactCheckBonus  = get_option_value_int("Rook Contact Check Bonus");
     QueenCheckBonus        = get_option_value_int("Queen Check Bonus");
     RookCheckBonus         = get_option_value_int("Rook Check Bonus");
     BishopCheckBonus       = get_option_value_int("Bishop Check Bonus");

src/main.cpp

@@ -71,16 +71,18 @@ int main(int argc, char *argv[]) {
   // Process command line arguments
   if (argc >= 2 && string(argv[1]) == "bench")
   {
-      if (argc < 4 || argc > 6)
+      if (argc < 4 || argc > 7)
       {
         std::cout << "Usage: glaurung bench <hash size> <threads> "
-                  << "[time = 60s] [fen positions file = default]"
+                  << "[time = 60s] [fen positions file = default] "
+                  << "[time, depth or node limited = time]"
                   << std::endl;
         exit(0);
       }
       string time = argc > 4 ? argv[4] : "60";
       string fen = argc > 5 ? argv[5] : "default";
-      benchmark(string(argv[2]) + " " + string(argv[3]) + " " + time + " " + fen);
+      string lim = argc > 6 ? argv[6] : "time";
+      benchmark(string(argv[2]) + " " + string(argv[3]) + " " + time + " " + fen + " " + lim);
       return 0;
   }
 

src/material.cpp

@@ -161,6 +161,22 @@ MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
       mi->evaluationFunction = &EvaluateKKX;
       return mi;
   }
+  else if (   pos.pawns() == EmptyBoardBB
+           && pos.rooks() == EmptyBoardBB
+           && pos.queens() == EmptyBoardBB)
+  {
+      // Minor piece endgame with at least one minor piece per side,
+      // and no pawns.
+      assert(pos.knights(WHITE) | pos.bishops(WHITE));
+      assert(pos.knights(BLACK) | pos.bishops(BLACK));
+
+      if (   pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
+          && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
+      {
+          mi->evaluationFunction = &EvaluateKmmKm;
+          return mi;
+      }
+  }
 
   // OK, we didn't find any special evaluation function for the current
   // material configuration. Is there a suitable scaling function?
@@ -221,6 +237,18 @@ MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
       }
   }
 
+  // Compute the space weight
+  if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >=
+      2*QueenValueMidgame + 4*RookValueMidgame + 2*KnightValueMidgame)
+  {
+      int minorPieceCount =  pos.piece_count(WHITE, KNIGHT)
+                           + pos.piece_count(BLACK, KNIGHT)
+                           + pos.piece_count(WHITE, BISHOP)
+                           + pos.piece_count(BLACK, BISHOP);
+
+      mi->spaceWeight = minorPieceCount * minorPieceCount;
+  }
+
   // Evaluate the material balance
 
   int sign;
@@ -309,6 +337,8 @@ EndgameFunctions::EndgameFunctions() {
   add(z[W][KNIGHT][1] ^ z[B][ROOK][1],   &EvaluateKNKR);
   add(z[W][QUEEN][1]  ^ z[B][ROOK][1],   &EvaluateKQKR);
   add(z[W][ROOK][1]   ^ z[B][QUEEN][1],  &EvaluateKRKQ);
+  add(z[W][BISHOP][2] ^ z[B][KNIGHT][1], &EvaluateKBBKN);
+  add(z[W][KNIGHT][1] ^ z[B][BISHOP][2], &EvaluateKNKBB);
 
   add(z[W][KNIGHT][1] ^ z[W][PAWN][1], W, &ScaleKNPK);
   add(z[B][KNIGHT][1] ^ z[B][PAWN][1], B, &ScaleKKNP);

src/material.h

@@ -52,6 +52,7 @@ public:
   Value mg_value() const;
   Value eg_value() const;
   ScaleFactor scale_factor(const Position& pos, Color c) const;
+  int space_weight() const;
   bool specialized_eval_exists() const;
   Value evaluate(const Position& pos) const;
 
@@ -64,6 +65,7 @@ private:
   uint8_t factor[2];
   EndgameEvaluationFunction* evaluationFunction;
   ScalingFunction* scalingFunction[2];
+  uint8_t spaceWeight;
 };
 
 
@@ -120,6 +122,7 @@ inline void MaterialInfo::clear() {
 
   mgValue = egValue = 0;
   factor[WHITE] = factor[BLACK] = uint8_t(SCALE_FACTOR_NORMAL);
+  spaceWeight = 0;
   evaluationFunction = NULL;
   scalingFunction[WHITE] = scalingFunction[BLACK] = NULL;
 }
@@ -144,6 +147,15 @@ inline ScaleFactor MaterialInfo::scale_factor(const Position& pos, Color c) cons
 }
 
 
+/// MaterialInfo::space_weight() simply returns the weight for the space
+/// evaluation for this material configuration.
+
+inline int MaterialInfo::space_weight() const {
+
+  return spaceWeight;
+}
+
+
 /// MaterialInfo::specialized_eval_exists decides whether there is a
 /// specialized evaluation function for the current material configuration,
 /// or if the normal evaluation function should be used.

src/misc.cpp

@@ -37,6 +37,7 @@ int gettimeofday(struct timeval * tp, struct timezone * tzp);
 
 #endif
 
+#include <cassert>
 #include <cstdio>
 #include <iomanip>
 #include <iostream>
@@ -49,6 +50,9 @@ int gettimeofday(struct timeval * tp, struct timezone * tzp);
 //// Variables
 ////
 
+static const std::string AppName = "Stockfish";
+static const std::string AppTag  = "";
+
 long dbg_cnt0 = 0;
 long dbg_cnt1 = 0;
 
@@ -60,6 +64,42 @@ bool dbg_show_hit_rate = false;
 //// Functions
 ////
 
+void dbg_hit_on(bool b) {
+
+    assert(!dbg_show_mean);
+    dbg_show_hit_rate = true;
+    dbg_cnt0++;
+    if (b)
+        dbg_cnt1++;
+}
+
+void dbg_hit_on_c(bool c, bool b) {
+
+    if (c)
+        dbg_hit_on(b);
+}
+
+void dbg_before() {
+
+    assert(!dbg_show_mean);
+    dbg_show_hit_rate = true;
+    dbg_cnt0++;
+}
+
+void dbg_after() {
+
+    assert(!dbg_show_mean);
+    dbg_show_hit_rate = true;
+    dbg_cnt1++;
+}
+
+void dbg_mean_of(int v) {
+
+    assert(!dbg_show_hit_rate);
+    dbg_cnt0++;
+    dbg_cnt1 += v;
+}
+
 void dbg_print_hit_rate() {
 
   std::cout << "Total " << dbg_cnt0 << " Hit " << dbg_cnt1
@@ -73,6 +113,19 @@ void dbg_print_mean() {
             << (float)dbg_cnt1 / (dbg_cnt0 ? dbg_cnt0 : 1) << std::endl;
 }
 
+void dbg_print_hit_rate(std::ofstream& logFile) {
+
+  logFile << "Total " << dbg_cnt0 << " Hit " << dbg_cnt1
+          << " hit rate (%) " << (dbg_cnt1*100)/(dbg_cnt0 ? dbg_cnt0 : 1)
+          << std::endl;
+}
+
+void dbg_print_mean(std::ofstream& logFile) {
+
+  logFile << "Total " << dbg_cnt0 << " Mean "
+          << (float)dbg_cnt1 / (dbg_cnt0 ? dbg_cnt0 : 1) << std::endl;
+}
+
 /// engine_name() returns the full name of the current Stockfish version.
 /// This will be either "Stockfish YYMMDD" (where YYMMDD is the date when the
 /// program was compiled) or "Stockfish <version number>", depending on whether
@@ -90,7 +143,9 @@ const std::string engine_name() {
       std::stringstream s;
       std::string day = (date[4] == ' ' ? date.substr(5, 1) : date.substr(4, 2));
 
-      s << "Stockfish " << date.substr(date.length() - 2) << std::setfill('0')
+      std::string name = AppName + " " + AppTag + " ";
+
+      s << name << date.substr(date.length() - 2) << std::setfill('0')
         << std::setw(2) << mon << std::setw(2) << day;
 
       return s.str();

src/misc.h

@@ -26,6 +26,7 @@
 //// Includes
 ////
 
+#include <fstream>
 #include <string>
 
 
@@ -37,7 +38,7 @@
 /// Version number.  If this is left empty, the current date (in the format
 /// YYMMDD) is used as a version number.
 
-const std::string EngineVersion = "1.01";
+const std::string EngineVersion = "1.2";
 
 
 ////
@@ -60,21 +61,21 @@ extern int Bioskey();
 ////
 //// Debug
 ////
-extern long dbg_cnt0;
-extern long dbg_cnt1;
-
-inline void dbg_hit_on(bool b) { dbg_cnt0++; if (b) dbg_cnt1++; }
-inline void dbg_hit_on_c(bool c, bool b) { if (c) dbg_hit_on(b); }
-
-inline void dbg_before() { dbg_cnt0++; }
-inline void dbg_after() { dbg_cnt1++; }
-
-inline void dbg_mean_of(int v) { dbg_cnt0++; dbg_cnt1 += v; }
-
-extern void dbg_print_hit_rate();
-extern void dbg_print_mean();
 
 extern bool dbg_show_mean;
 extern bool dbg_show_hit_rate;
 
+extern long dbg_cnt0;
+extern long dbg_cnt1;
+
+extern void dbg_hit_on(bool b);
+extern void dbg_hit_on_c(bool c, bool b);
+extern void dbg_before();
+extern void dbg_after();
+extern void dbg_mean_of(int v);
+extern void dbg_print_hit_rate();
+extern void dbg_print_mean();
+extern void dbg_print_hit_rate(std::ofstream& logFile);
+extern void dbg_print_mean(std::ofstream& logFile);
+
 #endif // !defined(MISC_H_INCLUDED)

src/movegen.cpp

@@ -122,15 +122,16 @@ int generate_captures(const Position& pos, MoveStack* mlist) {
   Bitboard target = pos.pieces_of_color(opposite_color(us));
   MoveStack* mlist_start = mlist;
 
+  mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
+  mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
+  mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
+  mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
+
   if (us == WHITE)
       mlist = generate_pawn_captures<WHITE>(pos, mlist);
   else
       mlist = generate_pawn_captures<BLACK>(pos, mlist);
 
-  mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
-  mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
-  mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
-  mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
   mlist = generate_piece_moves<KING>(pos, mlist, us, target);
   return int(mlist - mlist_start);
 }

src/movepick.cpp

@@ -26,6 +26,7 @@
 #include <cassert>
 
 #include "history.h"
+#include "evaluate.h"
 #include "movegen.h"
 #include "movepick.h"
 #include "search.h"
@@ -44,7 +45,9 @@ namespace {
   int MainSearchPhaseIndex;
   int EvasionsPhaseIndex;
   int QsearchWithChecksPhaseIndex;
+  int QsearchNoCapturesPhaseIndex;
   int QsearchWithoutChecksPhaseIndex;
+  int NoMovesPhaseIndex;
 
 }
 
@@ -62,28 +65,38 @@ namespace {
 /// search captures, promotions and some checks) and about how important good
 /// move ordering is at the current node.
 
-MovePicker::MovePicker(const Position& p, bool pvnode, Move ttm, Move mk,
-                       Move k1, Move k2, Depth d) : pos(p) {
-  pvNode = pvnode;
+MovePicker::MovePicker(const Position& p, bool pv, Move ttm,
+                       const SearchStack& ss, Depth d, EvalInfo* ei) : pos(p) {
+  pvNode = pv;
   ttMove = ttm;
-  mateKiller = (mk == ttm)? MOVE_NONE : mk;
-  killer1 = k1;
-  killer2 = k2;
+  mateKiller = (ss.mateKiller == ttm)? MOVE_NONE : ss.mateKiller;
+  killer1 = ss.killers[0];
+  killer2 = ss.killers[1];
   depth = d;
   movesPicked = 0;
   numOfMoves = 0;
   numOfBadCaptures = 0;
-  dc = p.discovered_check_candidates(p.side_to_move());
+
+  // With EvalInfo we are able to know how many captures are possible before
+  // generating them. So avoid generating in case we know are zero.
+  Color us = pos.side_to_move();
+  Color them = opposite_color(us);
+  bool noCaptures =    ei
+                   && (ei->attackedBy[us][0] & pos.pieces_of_color(them)) == 0
+                   && !ei->mi->specialized_eval_exists()
+                   && (pos.ep_square() == SQ_NONE)
+                   && !pos.has_pawn_on_7th(us);
 
   if (p.is_check())
-    phaseIndex = EvasionsPhaseIndex;
+      phaseIndex = EvasionsPhaseIndex;
   else if (depth > Depth(0))
-    phaseIndex = MainSearchPhaseIndex;
+      phaseIndex = MainSearchPhaseIndex;
   else if (depth == Depth(0))
-    phaseIndex = QsearchWithChecksPhaseIndex;
+      phaseIndex = (noCaptures ? QsearchNoCapturesPhaseIndex : QsearchWithChecksPhaseIndex);
   else
-    phaseIndex = QsearchWithoutChecksPhaseIndex;
+      phaseIndex = (noCaptures ? NoMovesPhaseIndex : QsearchWithoutChecksPhaseIndex);
 
+  dc = p.discovered_check_candidates(us);
   pinned = p.pinned_pieces(p.side_to_move());
 
   finished = false;
@@ -211,6 +224,8 @@ void MovePicker::score_captures() {
   // where it is possible to recapture with the hanging piece). Exchanging
   // big pieces before capturing a hanging piece probably helps to reduce
   // the subtree size.
+  // While scoring captures it moves all captures with negative SEE values
+  // to the badCaptures[] array.
   Move m;
   int seeValue;
 
@@ -225,8 +240,15 @@ void MovePicker::score_captures() {
           else
               moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m)))
                               -int(pos.type_of_piece_on(move_from(m)));
-      } else
+      }
+      else
+      {
+          // Losing capture, move it to the badCaptures[] array
+          assert(numOfBadCaptures < 63);
           moves[i].score = seeValue;
+          badCaptures[numOfBadCaptures++] = moves[i];
+          moves[i--] = moves[--numOfMoves];
+      }
   }
 }
 
@@ -248,10 +270,11 @@ void MovePicker::score_noncaptures() {
       else
           hs = H.move_ordering_score(pos.piece_on(move_from(m)), m);
 
-      // Ensure moves in history are always sorted as first
+      // Ensure history is always preferred to pst
       if (hs > 0)
           hs += 1000;
 
+      // pst based scoring
       moves[i].score = hs + pos.mg_pst_delta(m);
   }
 }
@@ -270,7 +293,6 @@ void MovePicker::score_evasions() {
       } else
           moves[i].score = H.move_ordering_score(pos.piece_on(move_from(m)), m);
   }
-  // FIXME try psqt also here
 }
 
 void MovePicker::score_qcaptures() {
@@ -288,8 +310,11 @@ void MovePicker::score_qcaptures() {
 }
 
 
-/// find_best_index() loops across the moves and returns index of
-/// the highest scored one.
+/// find_best_index() loops across the moves and returns index of
+/// the highest scored one. There is also a second version that
+/// lowers the priority of moves that attack the same square,
+/// so that if the best move that attack a square fails the next
+/// move picked attacks a different square if any, not the same one.
 
 int MovePicker::find_best_index() {
 
@@ -304,14 +329,48 @@ int MovePicker::find_best_index() {
   return bestIndex;
 }
 
+int MovePicker::find_best_index(Bitboard* squares, int values[]) {
+
+  int hs;
+  Move m;
+  Square to;
+  int bestScore = -10000000, bestIndex = -1;
+
+  for (int i = movesPicked; i < numOfMoves; i++)
+  {
+      m = moves[i].move;
+      to = move_to(m);
+      
+      if (!bit_is_set(*squares, to))
+      {
+          // Init at first use
+          set_bit(squares, to);
+          values[to] = 0;
+      }
+
+      hs = moves[i].score - values[to];
+      if (hs > bestScore)
+      {
+          bestIndex = i;
+          bestScore = hs;
+      }
+  }
+
+  if (bestIndex != -1)
+  {
+      // Raise value of the picked square, so next attack
+      // to the same square will get low priority.
+      to = move_to(moves[bestIndex].move);
+      values[to] += 0xB00;
+  }
+  return bestIndex;
+}
+
 
 /// MovePicker::pick_move_from_list() picks the move with the biggest score
 /// from a list of generated moves (moves[] or badCaptures[], depending on
 /// the current move generation phase).  It takes care not to return the
 /// transposition table move if that has already been serched previously.
-/// While picking captures in the PH_GOOD_CAPTURES phase (i.e. while picking
-/// non-losing captures in the main search), it moves all captures with
-/// negative SEE values to the badCaptures[] array.
 
 Move MovePicker::pick_move_from_list() {
 
@@ -325,23 +384,8 @@ Move MovePicker::pick_move_from_list() {
 
       while (movesPicked < numOfMoves)
       {
-          int bestScore = -10000000;
-          bestIndex = -1;
-          for (int i = movesPicked; i < numOfMoves; i++)
-          {
-              if (moves[i].score < 0)
-              {
-                  // Losing capture, move it to the badCaptures[] array
-                  assert(numOfBadCaptures < 63);
-                  badCaptures[numOfBadCaptures++] = moves[i];
-                  moves[i--] = moves[--numOfMoves];
-              }
-              else if (moves[i].score > bestScore)
-              {
-                  bestIndex = i;
-                  bestScore = moves[i].score;
-              }
-          }
+          bestIndex = find_best_index();
+
           if (bestIndex != -1) // Found a good capture
           {
               move = moves[bestIndex].move;
@@ -461,8 +505,9 @@ MovePicker::MovegenPhase MovePicker::current_move_type() const {
 
 /// MovePicker::init_phase_table() initializes the PhaseTable[],
 /// MainSearchPhaseIndex, EvasionPhaseIndex, QsearchWithChecksPhaseIndex
-/// and QsearchWithoutChecksPhaseIndex variables. It is only called once
-/// during program startup, and never again while the program is running.
+/// QsearchNoCapturesPhaseIndex, QsearchWithoutChecksPhaseIndex and
+/// NoMovesPhaseIndex variables. It is only called once during program
+/// startup, and never again while the program is running.
 
 void MovePicker::init_phase_table() {
 
@@ -491,8 +536,17 @@ void MovePicker::init_phase_table() {
   PhaseTable[i++] = PH_QCHECKS;
   PhaseTable[i++] = PH_STOP;
 
+  // Quiescence search with checks only and no captures
+  QsearchNoCapturesPhaseIndex = i - 1;
+  PhaseTable[i++] = PH_QCHECKS;
+  PhaseTable[i++] = PH_STOP;
+
   // Quiescence search without checks
   QsearchWithoutChecksPhaseIndex = i - 1;
   PhaseTable[i++] = PH_QCAPTURES;
   PhaseTable[i++] = PH_STOP;
+
+  // Do not generate any move
+  NoMovesPhaseIndex = i - 1;
+  PhaseTable[i++] = PH_STOP;
 }

src/movepick.h

@@ -34,6 +34,9 @@
 //// Types
 ////
 
+struct EvalInfo;
+struct SearchStack;
+
 /// MovePicker is a class which is used to pick one legal move at a time from
 /// the current position.  It is initialized with a Position object and a few
 /// moves we have reason to believe are good.  The most important method is
@@ -60,7 +63,7 @@ public:
     PH_STOP
   };
 
-  MovePicker(const Position& p, bool pvnode, Move ttm, Move mk, Move k1, Move k2, Depth d);
+  MovePicker(const Position& p, bool pvnode, Move ttm, const SearchStack& ss, Depth d, EvalInfo* ei = NULL);
   Move get_next_move();
   Move get_next_move(Lock &lock);
   int number_of_moves() const;
@@ -77,6 +80,7 @@ private:
   void score_qcaptures();
   Move pick_move_from_list();
   int find_best_index();
+  int find_best_index(Bitboard* squares, int values[]);
 
   const Position& pos;
   Move ttMove, mateKiller, killer1, killer2;

src/pawns.cpp

@@ -86,40 +86,37 @@ namespace {
 
   // Candidate passed pawn bonus by rank, middle game.
   const Value CandidateMidgameBonus[8] = {
-    Value(0), Value(12), Value(12), Value(20),
-    Value(40), Value(90), Value(0), Value(0)
+    Value( 0), Value(12), Value(12), Value(20),
+    Value(40), Value(90), Value( 0), Value( 0)
   };
 
   // Candidate passed pawn bonus by rank, endgame.
   const Value CandidateEndgameBonus[8] = {
-    Value(0), Value(24), Value(24), Value(40),
-    Value(80), Value(180), Value(0), Value(0)
+    Value( 0), Value(24), Value(24), Value(40),
+    Value(80), Value(180), Value(0), Value( 0)
   };
 
-  // Evaluate pawn storms?
-  const bool EvaluatePawnStorms = true;
-
   // Pawn storm tables for positions with opposite castling:
   const int QStormTable[64] = {
-    0, 0, 0, 0, 0, 0, 0, 0,
-    -22, -22, -22, -13, -4, 0, 0, 0,
-    -4, -9, -9, -9, -4, 0, 0, 0,
+    0,  0,  0,  0, 0, 0, 0, 0,
+  -22,-22,-22,-13,-4, 0, 0, 0,
+   -4, -9, -9, -9,-4, 0, 0, 0,
     9, 18, 22, 18, 9, 0, 0, 0,
-    22, 31, 31, 22, 0, 0, 0, 0,
-    31, 40, 40, 31, 0, 0, 0, 0,
-    31, 40, 40, 31, 0, 0, 0, 0,
-    0, 0, 0, 0, 0, 0, 0, 0
+   22, 31, 31, 22, 0, 0, 0, 0,
+   31, 40, 40, 31, 0, 0, 0, 0,
+   31, 40, 40, 31, 0, 0, 0, 0,
+    0,  0,  0,  0, 0, 0, 0, 0
   };
   
   const int KStormTable[64] = {
-    0, 0, 0, 0, 0, 0, 0, 0,
-    0, 0, 0, -4, -13, -22, -27, -27,
-    0, 0, 0, -4, -9, -13, -18, -18,
-    0, 0, 0, 0, 9, 9, 9, 9,
-    0, 0, 0, 0, 9, 18, 27, 27,
-    0, 0, 0, 0, 9, 27, 40, 36,
-    0, 0, 0, 0, 0, 31, 40, 31,
-    0, 0, 0, 0, 0, 0, 0, 0
+    0, 0, 0, 0,  0,  0,  0,  0,
+    0, 0, 0,-4,-13,-22,-27,-27,
+    0, 0, 0,-4, -9,-13,-18,-18,
+    0, 0, 0, 0,  9,  9,  9,  9,
+    0, 0, 0, 0,  9, 18, 27, 27,
+    0, 0, 0, 0,  9, 27, 40, 36,
+    0, 0, 0, 0,  0, 31, 40, 31,
+    0, 0, 0, 0,  0,  0,  0,  0
   };
 
   // Pawn storm open file bonuses by file:
@@ -141,14 +138,16 @@ namespace {
 /// Constructor
 
 PawnInfoTable::PawnInfoTable(unsigned numOfEntries) {
+
   size = numOfEntries;
   entries = new PawnInfo[size];
-  if(entries == NULL) {
-    std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo))
-              << " bytes for pawn hash table." << std::endl;
-    exit(EXIT_FAILURE);
+  if (entries == NULL)
+  {
+      std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo))
+                << " bytes for pawn hash table." << std::endl;
+      exit(EXIT_FAILURE);
   }
-  this->clear();
+  clear();
 }
 
 
@@ -173,6 +172,7 @@ void PawnInfoTable::clear() {
 /// the same pawn structure occurs again.
 
 PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) {
+
   assert(pos.is_ok());
 
   Key key = pos.get_pawn_key();
@@ -181,207 +181,204 @@ PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) {
 
   // If pi->key matches the position's pawn hash key, it means that we 
   // have analysed this pawn structure before, and we can simply return the
-  // information we found the last time instead of recomputing it:
-  if(pi->key == key)
-    return pi;
+  // information we found the last time instead of recomputing it
+  if (pi->key == key)
+      return pi;
 
-  // Clear the PawnInfo object, and set the key:
+  // Clear the PawnInfo object, and set the key
   pi->clear();
   pi->key = key;
 
   Value mgValue[2] = {Value(0), Value(0)};
   Value egValue[2] = {Value(0), Value(0)};
 
-  // Loop through the pawns for both colors:
-  for(Color us = WHITE; us <= BLACK; us++) {
+  // Loop through the pawns for both colors
+  for (Color us = WHITE; us <= BLACK; us++)
+  {
     Color them = opposite_color(us);
     Bitboard ourPawns = pos.pawns(us);
     Bitboard theirPawns = pos.pawns(them);
     Bitboard pawns = ourPawns;
 
-    // Initialize pawn storm scores by giving bonuses for open files:
-    if(EvaluatePawnStorms)
-      for(File f = FILE_A; f <= FILE_H; f++)
-        if(pos.file_is_half_open(us, f)) {
-          pi->ksStormValue[us] += KStormOpenFileBonus[f];
-          pi->qsStormValue[us] += QStormOpenFileBonus[f];
+    // Initialize pawn storm scores by giving bonuses for open files
+    for (File f = FILE_A; f <= FILE_H; f++)
+        if (pos.file_is_half_open(us, f))
+        {
+            pi->ksStormValue[us] += KStormOpenFileBonus[f];
+            pi->qsStormValue[us] += QStormOpenFileBonus[f];
         }
 
-    // Loop through all pawns of the current color and score each pawn:
-    while(pawns) {
-      Square s = pop_1st_bit(&pawns);
-      File f = square_file(s);
-      Rank r = square_rank(s);
-      bool passed, doubled, isolated, backward, chain, candidate;
-      int bonus;
+    // Loop through all pawns of the current color and score each pawn
+    while (pawns)
+    {
+        bool passed, doubled, isolated, backward, chain, candidate;
+        Square s = pop_1st_bit(&pawns);
+        File f = square_file(s);
+        Rank r = square_rank(s);
 
-      assert(pos.piece_on(s) == pawn_of_color(us));
+        assert(pos.piece_on(s) == pawn_of_color(us));
 
-      // The file containing the pawn is not half open:
-      pi->halfOpenFiles[us] &= ~(1 << f);
+        // The file containing the pawn is not half open
+        pi->halfOpenFiles[us] &= ~(1 << f);
 
-      // Passed, isolated or doubled pawn?
-      passed = pos.pawn_is_passed(us, s);
-      isolated = pos.pawn_is_isolated(us, s);
-      doubled = pos.pawn_is_doubled(us, s);
+        // Passed, isolated or doubled pawn?
+        passed = pos.pawn_is_passed(us, s);
+        isolated = pos.pawn_is_isolated(us, s);
+        doubled = pos.pawn_is_doubled(us, s);
 
-      if(EvaluatePawnStorms) {
-        // We calculate kingside and queenside pawn storm
-        // scores for both colors.  These are used when evaluating
-        // middle game positions with opposite side castling.
+        // We calculate kingside and queenside pawn storm scores
+        // for both colors. These are used when evaluating middle
+        // game positions with opposite side castling.
         //
         // Each pawn is given a base score given by a piece square table
-        // (KStormTable[] or QStormTable[]).  This score is increased if
+        // (KStormTable[] or QStormTable[]). This score is increased if
         // there are enemy pawns on adjacent files in front of the pawn.
         // This is because we want to be able to open files against the
         // enemy king, and to avoid blocking the pawn structure (e.g. white
         // pawns on h6, g5, black pawns on h7, g6, f7).
+
+        // Kingside and queenside pawn storms
+        int KBonus = KStormTable[relative_square(us, s)];
+        int QBonus = QStormTable[relative_square(us, s)];
+        bool outPostFlag = (KBonus > 0 && (outpost_mask(us, s) & theirPawns));
+        bool passedFlag = (QBonus > 0 && (passed_pawn_mask(us, s) & theirPawns));
+
+        switch (f) {
+
+        case FILE_A:
+            QBonus += passedFlag * QBonus / 2;
+            break;
+
+        case FILE_B:
+            QBonus += passedFlag * (QBonus / 2 + QBonus / 4);
+            break;
+
+        case FILE_C:
+            QBonus += passedFlag * QBonus / 2;
+            break;
+
+        case FILE_F:
+            KBonus += outPostFlag * KBonus / 4;
+            break;
+
+        case FILE_G:
+            KBonus += outPostFlag * (KBonus / 2 + KBonus / 4);
+            break;
+
+        case FILE_H:
+            KBonus += outPostFlag * KBonus / 2;
+            break;
+
+        default:
+            break;
+        }
+        pi->ksStormValue[us] += KBonus;
+        pi->qsStormValue[us] += QBonus;
+
+        // Member of a pawn chain (but not the backward one)? We could speed up
+        // the test a little by introducing an array of masks indexed by color
+        // and square for doing the test, but because everything is hashed,
+        // it probably won't make any noticable difference.
+        chain =  ourPawns
+               & neighboring_files_bb(f)
+               & (rank_bb(r) | rank_bb(r - (us == WHITE ? 1 : -1)));
+
+        // Test for backward pawn
+        //
+        // If the pawn is passed, isolated, or member of a pawn chain
+        // it cannot be backward. If can capture an enemy pawn or if
+        // there are friendly pawns behind on neighboring files it cannot
+        // be backward either.
+        if (   passed
+            || isolated
+            || chain
+            || (pos.pawn_attacks(us, s) & theirPawns)
+            || (ourPawns & behind_bb(us, r) & neighboring_files_bb(f)))
+            backward = false;
+        else
+        {
+            // We now know that there are no friendly pawns beside or behind this
+            // pawn on neighboring files. We now check whether the pawn is
+            // backward by looking in the forward direction on the neighboring
+            // files, and seeing whether we meet a friendly or an enemy pawn first.
+            Bitboard b;
+            if (us == WHITE)
+            {
+                for (b = pos.pawn_attacks(us, s); !(b & (ourPawns | theirPawns)); b <<= 8);
+                backward = (b | (b << 8)) & theirPawns;
+            }
+            else
+            {
+                for (b = pos.pawn_attacks(us, s); !(b & (ourPawns | theirPawns)); b >>= 8);
+                backward = (b | (b >> 8)) & theirPawns;
+            }
+        }
+
+        // Test for candidate passed pawn
+        candidate =    !passed
+                     && pos.file_is_half_open(them, f)
+                     && (  count_1s_max_15(neighboring_files_bb(f) & (behind_bb(us, r) | rank_bb(r)) & ourPawns)
+                         - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(us, r)              & theirPawns)
+                         >= 0);
+
+        // In order to prevent doubled passed pawns from receiving a too big
+        // bonus, only the frontmost passed pawn on each file is considered as
+        // a true passed pawn.
+        if (passed && (ourPawns & squares_in_front_of(us, s)))
+        {
+            // candidate = true;
+            passed = false;
+        }
+
+        // Score this pawn
+        Value mv = Value(0), ev = Value(0);
+        if (isolated)
+        {
+            mv -= IsolatedPawnMidgamePenalty[f];
+            ev -= IsolatedPawnEndgamePenalty[f];
+            if (pos.file_is_half_open(them, f))
+            {
+                mv -= IsolatedPawnMidgamePenalty[f] / 2;
+                ev -= IsolatedPawnEndgamePenalty[f] / 2;
+            }
+        }
+        if (doubled)
+        {
+            mv -= DoubledPawnMidgamePenalty[f];
+            ev -= DoubledPawnEndgamePenalty[f];
+        }
+        if (backward)
+        {
+            mv -= BackwardPawnMidgamePenalty[f];
+            ev -= BackwardPawnEndgamePenalty[f];
+            if (pos.file_is_half_open(them, f))
+            {
+                mv -= BackwardPawnMidgamePenalty[f] / 2;
+                ev -= BackwardPawnEndgamePenalty[f] / 2;
+            }
+        }
+        if (chain)
+        {
+            mv += ChainMidgameBonus[f];
+            ev += ChainEndgameBonus[f];
+        }
+        if (candidate)
+        {
+            mv += CandidateMidgameBonus[relative_rank(us, s)];
+            ev += CandidateEndgameBonus[relative_rank(us, s)];
+        }
+
+        mgValue[us] += mv;
+        egValue[us] += ev;
         
-        // Kingside pawn storms:
-        bonus = KStormTable[relative_square(us, s)];
-        if(bonus > 0 && outpost_mask(us, s) & theirPawns) {
-          switch(f) {
-
-          case FILE_F:
-            bonus += bonus / 4;
-            break;
-
-          case FILE_G:
-            bonus += bonus / 2 + bonus / 4;
-            break;
-
-          case FILE_H:
-            bonus += bonus / 2;
-            break;
-
-          default:
-            break;
-          }
-        }
-        pi->ksStormValue[us] += bonus;
-
-        // Queenside pawn storms:
-        bonus = QStormTable[relative_square(us, s)];
-        if(bonus > 0 && passed_pawn_mask(us, s) & theirPawns) {
-          switch(f) {
-
-          case FILE_A:
-            bonus += bonus / 2;
-            break;
-
-          case FILE_B:
-            bonus += bonus / 2 + bonus / 4;
-            break;
-
-          case FILE_C:
-            bonus += bonus / 2;
-            break;
-
-          default:
-            break;
-          }
-        }
-        pi->qsStormValue[us] += bonus;
-      }
-      
-      // Member of a pawn chain?  We could speed up the test a little by 
-      // introducing an array of masks indexed by color and square for doing
-      // the test, but because everything is hashed, it probably won't make
-      // any noticable difference.
-      chain = (us == WHITE)?
-        (ourPawns & neighboring_files_bb(f) & (rank_bb(r) | rank_bb(r-1))) :
-        (ourPawns & neighboring_files_bb(f) & (rank_bb(r) | rank_bb(r+1)));
-
-
-      // Test for backward pawn.
-
-      // If the pawn is isolated, passed, or member of a pawn chain, it cannot
-      // be backward:
-      if(passed || isolated || chain)
-        backward = false;
-      // If the pawn can capture an enemy pawn, it's not backward:
-      else if(pos.pawn_attacks(us, s) & theirPawns)
-        backward = false;
-      // Check for friendly pawns behind on neighboring files:
-      else if(ourPawns & in_front_bb(them, r) & neighboring_files_bb(f))
-        backward = false;
-      else {
-        // We now know that there is no friendly pawns beside or behind this
-        // pawn on neighboring files.  We now check whether the pawn is
-        // backward by looking in the forward direction on the neighboring
-        // files, and seeing whether we meet a friendly or an enemy pawn first.
-        Bitboard b;
-        if(us == WHITE) {
-          for(b=pos.pawn_attacks(us, s); !(b&(ourPawns|theirPawns)); b<<=8);
-          backward = (b | (b << 8)) & theirPawns;
-        }
-        else {
-          for(b=pos.pawn_attacks(us, s); !(b&(ourPawns|theirPawns)); b>>=8);
-          backward = (b | (b >> 8)) & theirPawns;
-        }
-      }
-
-      // Test for candidate passed pawn.
-      candidate =
-        (!passed && pos.file_is_half_open(them, f) &&
-         count_1s_max_15(neighboring_files_bb(f)
-                         & (in_front_bb(them, r) | rank_bb(r))
-                         & ourPawns)
-         - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(us, r)
-                           & theirPawns)
-         >= 0);
-
-      // In order to prevent doubled passed pawns from receiving a too big
-      // bonus, only the frontmost passed pawn on each file is considered as
-      // a true passed pawn.
-      if(passed && (ourPawns & squares_in_front_of(us, s))) {
-        // candidate = true;
-        passed = false;
-      }
-
-      // Score this pawn:
-      Value mv = Value(0), ev = Value(0);
-      if(isolated) {
-        mv -= IsolatedPawnMidgamePenalty[f];
-        ev -= IsolatedPawnEndgamePenalty[f];
-        if(pos.file_is_half_open(them, f)) {
-          mv -= IsolatedPawnMidgamePenalty[f] / 2;
-          ev -= IsolatedPawnEndgamePenalty[f] / 2;
-        }
-      }
-      if(doubled)  {
-        mv -= DoubledPawnMidgamePenalty[f];
-        ev -= DoubledPawnEndgamePenalty[f];
-      }
-      if(backward)  {
-        mv -= BackwardPawnMidgamePenalty[f];
-        ev -= BackwardPawnEndgamePenalty[f];
-        if(pos.file_is_half_open(them, f)) {
-          mv -= BackwardPawnMidgamePenalty[f] / 2;
-          ev -= BackwardPawnEndgamePenalty[f] / 2;
-        }
-      }
-      if(chain) {
-        mv += ChainMidgameBonus[f];
-        ev += ChainEndgameBonus[f];
-      }
-      if(candidate) {
-        mv += CandidateMidgameBonus[relative_rank(us, s)];
-        ev += CandidateEndgameBonus[relative_rank(us, s)];
-      }
-
-      mgValue[us] += mv;
-      egValue[us] += ev;
-        
-      // If the pawn is passed, set the square of the pawn in the passedPawns
-      // bitboard:
-      if(passed)
-        set_bit(&(pi->passedPawns), s);
-    }
-  }
+        // If the pawn is passed, set the square of the pawn in the passedPawns
+        // bitboard
+        if (passed)
+            set_bit(&(pi->passedPawns), s);
+    } // while(pawns)
+  } // for(colors)
 
   pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]);
   pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]);
-
   return pi;
 }

src/pawns.h

@@ -120,10 +120,10 @@ inline bool PawnInfo::has_open_file_to_right(Color c, File f) const {
 }
 
 inline void PawnInfo::clear() {
-  mgValue = egValue = 0;
-  passedPawns = EmptyBoardBB;
-  ksStormValue[WHITE] = ksStormValue[BLACK] = 0;
-  qsStormValue[WHITE] = qsStormValue[BLACK] = 0;
+
+  Key k = key;
+  memset(this, 0, sizeof(PawnInfo));
+  key = k;
   halfOpenFiles[WHITE] = halfOpenFiles[BLACK] = 0xFF;
 }
 

src/piece.cpp

@@ -72,7 +72,7 @@ const SquareDelta PawnPush[2] = {
 
 static const char PieceChars[] = " pnbrqk";
 
-char piece_type_to_char(PieceType pt, bool upcase = false) {
+char piece_type_to_char(PieceType pt, bool upcase) {
   return upcase? toupper(PieceChars[pt]) : PieceChars[pt];
 }
 

src/piece.h

@@ -124,7 +124,7 @@ inline SquareDelta pawn_push(Color c) {
 //// Prototypes
 ////
 
-extern char piece_type_to_char(PieceType pt, bool upcase);
+extern char piece_type_to_char(PieceType pt, bool upcase = false);
 extern PieceType piece_type_from_char(char c);
 extern bool piece_is_ok(Piece pc);
 extern bool piece_type_is_ok(PieceType pt);

src/position.cpp

@@ -31,6 +31,7 @@
 #include "movepick.h"
 #include "position.h"
 #include "psqtab.h"
+#include "san.h"
 #include "ucioption.h"
 
 
@@ -38,6 +39,8 @@
 //// Variables
 ////
 
+extern SearchStack EmptySearchStack;
+
 int Position::castleRightsMask[64];
 
 Key Position::zobrist[2][8][64];
@@ -49,6 +52,7 @@ Key Position::zobSideToMove;
 Value Position::MgPieceSquareTable[16][64];
 Value Position::EgPieceSquareTable[16][64];
 
+static bool RequestPending = false;
 
 ////
 //// Functions
@@ -242,7 +246,7 @@ const std::string Position::to_fen() const {
 
       fen += (rank > RANK_1 ? '/' : ' ');
   }
-  fen += (sideToMove == WHITE ? 'w' : 'b') + ' ';
+  fen += (sideToMove == WHITE ? "w " : "b ");
   if (castleRights != NO_CASTLES)
   {
     if (can_castle_kingside(WHITE))  fen += 'K';
@@ -263,29 +267,45 @@ const std::string Position::to_fen() const {
 
 
 /// Position::print() prints an ASCII representation of the position to
-/// the standard output.
+/// the standard output. If a move is given then also the san is print.
 
-void Position::print() const {
-  char pieceStrings[][8] =
-    {"| ? ", "| P ", "| N ", "| B ", "| R ", "| Q ", "| K ", "| ? ",
-     "| ? ", "|=P=", "|=N=", "|=B=", "|=R=", "|=Q=", "|=K="
-    };
+void Position::print(Move m) const {
 
-  for(Rank rank = RANK_8; rank >= RANK_1; rank--) {
-    std::cout << "+---+---+---+---+---+---+---+---+\n";
-    for(File file = FILE_A; file <= FILE_H; file++) {
-      Square sq = make_square(file, rank);
-      Piece piece = piece_on(sq);
-      if(piece == EMPTY)
-        std::cout << ((square_color(sq) == WHITE)? "|   " : "| . ");
-      else
-        std::cout << pieceStrings[piece];
-    }
-    std::cout << "|\n";
+  static const std::string pieceLetters = " PNBRQK  PNBRQK .";
+
+  // Check for reentrancy, as example when called from inside
+  // MovePicker that is used also here in move_to_san()
+  if (RequestPending)
+      return;
+
+  RequestPending = true;
+
+  std::cout << std::endl;
+  if (m != MOVE_NONE)
+  {
+      std::string col = (color_of_piece_on(move_from(m)) == BLACK ? ".." : "");
+      std::cout << "Move is: " << col << move_to_san(*this, m) << std::endl;
   }
-  std::cout << "+---+---+---+---+---+---+---+---+\n";
-  std::cout << to_fen() << std::endl;
-  std::cout << key << std::endl;
+  for (Rank rank = RANK_8; rank >= RANK_1; rank--)
+  {
+      std::cout << "+---+---+---+---+---+---+---+---+" << std::endl;
+      for (File file = FILE_A; file <= FILE_H; file++)
+      {
+          Square sq = make_square(file, rank);
+          Piece piece = piece_on(sq);
+          if (piece == EMPTY && square_color(sq) == WHITE)
+              piece = NO_PIECE;
+
+          char col = (color_of_piece_on(sq) == BLACK ? '=' : ' ');
+          std::cout << '|' << col << pieceLetters[piece] << col;
+      }
+      std::cout << '|' << std::endl;
+  }
+  std::cout << "+---+---+---+---+---+---+---+---+" << std::endl
+            << "Fen is: " << to_fen() << std::endl
+            << "Key is: " << key << std::endl;
+
+  RequestPending = false;
 }
 
 
@@ -655,10 +675,12 @@ bool Position::move_is_check(Move m, Bitboard dcCandidates) const {
 
 
 /// Position::move_is_capture() tests whether a move from the current
-/// position is a capture.
+/// position is a capture. Move must not be MOVE_NONE.
 
 bool Position::move_is_capture(Move m) const {
 
+  assert(m != MOVE_NONE);
+
   return (   !square_is_empty(move_to(m))
           && (color_of_piece_on(move_to(m)) == opposite_color(side_to_move()))
          )
@@ -1560,10 +1582,16 @@ void Position::undo_null_move(const UndoInfo &u) {
 
 
 /// Position::see() is a static exchange evaluator:  It tries to estimate the
-/// material gain or loss resulting from a move.  There are two versions of
-/// this function: One which takes a move as input, and one which takes a
-/// 'from' and a 'to' square.  The function does not yet understand promotions
-/// or en passant captures.
+/// material gain or loss resulting from a move.  There are three versions of
+/// this function: One which takes a destination square as input, one takes a
+/// move, and one which takes a 'from' and a 'to' square.  The function does
+/// not yet understand promotions or en passant captures.
+
+int Position::see(Square to) const {
+
+  assert(square_is_ok(to));
+  return see(SQ_NONE, to);
+}
 
 int Position::see(Move m) const {
 
@@ -1573,18 +1601,22 @@ int Position::see(Move m) const {
 
 int Position::see(Square from, Square to) const {
 
-  // Approximate material values, with pawn = 1
+  // Material values
   static const int seeValues[18] = {
-    0, 1, 3, 3, 5, 10, 100, 0, 0, 1, 3, 3, 5, 10, 100, 0, 0, 0
+    0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
+       RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0,
+    0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
+       RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0,
+    0, 0
   };
 
   Bitboard attackers, occ, b;
 
-  assert(square_is_ok(from));
+  assert(square_is_ok(from) || from == SQ_NONE);
   assert(square_is_ok(to));
 
   // Initialize colors
-  Color us = color_of_piece_on(from);
+  Color us = (from != SQ_NONE ? color_of_piece_on(from) : opposite_color(color_of_piece_on(to)));
   Color them = opposite_color(us);
 
   // Initialize pieces
@@ -1594,15 +1626,49 @@ int Position::see(Square from, Square to) const {
   // Find all attackers to the destination square, with the moving piece
   // removed, but possibly an X-ray attacker added behind it.
   occ = occupied_squares();
-  clear_bit(&occ, from);
-  attackers =  (rook_attacks_bb(to, occ)   & rooks_and_queens())
-             | (bishop_attacks_bb(to, occ) & bishops_and_queens())
-             | (piece_attacks<KNIGHT>(to)  & knights())
-             | (piece_attacks<KING>(to)    & kings())
-             | (pawn_attacks(WHITE, to)    & pawns(BLACK))
-             | (pawn_attacks(BLACK, to)    & pawns(WHITE));
 
-  // If the opponent has no attackers, we are finished
+  // Handle enpassant moves
+  if (ep_square() == to && type_of_piece_on(from) == PAWN)
+  {
+      assert(capture == EMPTY);
+
+      Square capQq = (side_to_move() == WHITE)? (to - DELTA_N) : (to - DELTA_S);
+      capture = piece_on(capQq);
+
+      assert(type_of_piece_on(capQq) == PAWN);
+
+      // Remove the captured pawn
+      clear_bit(&occ, capQq);
+  }
+
+  while (true)
+  {
+      clear_bit(&occ, from);
+      attackers =  (rook_attacks_bb(to, occ)   & rooks_and_queens())
+                 | (bishop_attacks_bb(to, occ) & bishops_and_queens())
+                 | (piece_attacks<KNIGHT>(to)  & knights())
+                 | (piece_attacks<KING>(to)    & kings())
+                 | (pawn_attacks(WHITE, to)    & pawns(BLACK))
+                 | (pawn_attacks(BLACK, to)    & pawns(WHITE));
+
+      if (from != SQ_NONE)
+          break;
+
+      // If we don't have any attacker we are finished
+      if ((attackers & pieces_of_color(us)) == EmptyBoardBB)
+          return 0;
+
+      // Locate the least valuable attacker to the destination square
+      // and use it to initialize from square.
+      PieceType pt;
+      for (pt = PAWN; !(attackers & pieces_of_color_and_type(us, pt)); pt++)
+          assert(pt < KING);
+
+      from = first_1(attackers & pieces_of_color_and_type(us, pt));
+      piece = piece_on(from);
+  }
+
+  // If the opponent has no attackers we are finished
   if ((attackers & pieces_of_color(them)) == EmptyBoardBB)
       return seeValues[capture];
 
@@ -1905,8 +1971,7 @@ bool Position::is_mate() {
 
   if (is_check())
   {
-      MovePicker mp = MovePicker(*this, false, MOVE_NONE, MOVE_NONE,
-                                 MOVE_NONE, MOVE_NONE, Depth(0));
+      MovePicker mp = MovePicker(*this, false, MOVE_NONE, EmptySearchStack, Depth(0));
       return mp.get_next_move() == MOVE_NONE;
   }
   return false;

src/position.h

@@ -128,7 +128,7 @@ public:
   // Text input/output
   void from_fen(const std::string &fen);
   const std::string to_fen() const;
-  void print() const;
+  void print(Move m = MOVE_NONE) const;
 
   // Copying
   void copy(const Position &pos);
@@ -174,13 +174,13 @@ public:
   // Number of pieces of each color and type
   int piece_count(Color c, PieceType pt) const;
 
-  // The en passant square:
+  // The en passant square
   Square ep_square() const;
 
   // Current king position for each color
   Square king_square(Color c) const;
 
-  // Castling rights.
+  // Castling rights
   bool can_castle_kingside(Color c) const;
   bool can_castle_queenside(Color c) const;
   bool can_castle(Color c) const;
@@ -253,6 +253,7 @@ public:
   // Static exchange evaluation
   int see(Square from, Square to) const;
   int see(Move m) const;
+  int see(Square to) const;
 
   // Accessing hash keys
   Key get_key() const;

src/san.cpp

@@ -31,6 +31,7 @@
 #include "movepick.h"
 #include "san.h"
 
+extern SearchStack EmptySearchStack;
 
 ////
 //// Local definitions
@@ -50,7 +51,7 @@ namespace {
 
   /// Functions
 
-  Ambiguity move_ambiguity(Position &pos, Move m);
+  Ambiguity move_ambiguity(const Position& pos, Move m);
   const std::string time_string(int milliseconds);
   const std::string score_string(Value v);
 }
@@ -61,206 +62,222 @@ namespace {
 ////
 
 /// move_to_san() takes a position and a move as input, where it is assumed
-/// that the move is a legal move from the position.  The return value is
+/// that the move is a legal move from the position. The return value is
 /// a string containing the move in short algebraic notation.
 
-const std::string move_to_san(Position &pos, Move m) {
-  std::string str;
+const std::string move_to_san(const Position& pos, Move m) {
 
   assert(pos.is_ok());
   assert(move_is_ok(m));
 
-  if(m == MOVE_NONE) {
-    str = "(none)";
-    return str;
-  }
-  else if(m == MOVE_NULL) {
-    str = "(null)";
-    return str;
-  }
-  else if(move_is_long_castle(m))
-    str = "O-O-O";
-  else if(move_is_short_castle(m))
-    str = "O-O";
-  else {
-    Square from, to;
-    Piece pc;
+  std::string san = "";
 
-    from = move_from(m);
-    to = move_to(m);
-    pc = pos.piece_on(move_from(m));
-
-    str = "";
-
-    if(type_of_piece(pc) == PAWN) {
-      if(pos.move_is_capture(m))
-        str += file_to_char(square_file(move_from(m)));
-    }
-    else {
-      str += piece_type_to_char(type_of_piece(pc), true);
-
-      Ambiguity amb = move_ambiguity(pos, m);
-      switch(amb) {
-
-      case AMBIGUITY_NONE:
-        break;
-
-      case AMBIGUITY_FILE:
-        str += file_to_char(square_file(from));
-        break;
-
-      case AMBIGUITY_RANK:
-        str += rank_to_char(square_rank(from));
-        break;
-
-      case AMBIGUITY_BOTH:
-        str += square_to_string(from);
-        break;
-
-      default:
-        assert(false);
+  if (m == MOVE_NONE)
+      return "(none)";
+  else if (m == MOVE_NULL)
+      return "(null)";
+  else if (move_is_long_castle(m))
+      san = "O-O-O";
+  else if (move_is_short_castle(m))
+      san = "O-O";
+  else
+  {
+      Piece pc = pos.piece_on(move_from(m));
+      if (type_of_piece(pc) != PAWN)
+      {
+          san += piece_type_to_char(type_of_piece(pc), true);
+          Square from = move_from(m);
+          switch (move_ambiguity(pos, m)) {
+          case AMBIGUITY_NONE:
+            break;
+          case AMBIGUITY_FILE:
+            san += file_to_char(square_file(from));
+            break;
+          case AMBIGUITY_RANK:
+            san += rank_to_char(square_rank(from));
+            break;
+          case AMBIGUITY_BOTH:
+            san += square_to_string(from);
+            break;
+          default:
+            assert(false);
+          }
+      }
+      if (pos.move_is_capture(m))
+      {
+          if (type_of_piece(pc) == PAWN)
+              san += file_to_char(square_file(move_from(m)));
+          san += "x";
+      }
+      san += square_to_string(move_to(m));
+      if (move_promotion(m))
+      {
+          san += '=';
+          san += piece_type_to_char(move_promotion(m), true);
       }
-    }
-
-    if(pos.move_is_capture(m))
-      str += "x";
-
-    str += square_to_string(move_to(m));
-
-    if(move_promotion(m)) {
-      str += "=";
-      str += piece_type_to_char(move_promotion(m), true);
-    }
   }
-
   // Is the move check?  We don't use pos.move_is_check(m) here, because
   // Position::move_is_check doesn't detect all checks (not castling moves,
   // promotions and en passant captures).
   UndoInfo u;
-  pos.do_move(m, u);
-  if(pos.is_check())
-    str += pos.is_mate()? "#" : "+";
-  pos.undo_move(m, u);
+  Position p(pos);
+  p.do_move(m, u);
+  if (p.is_check())
+      san += p.is_mate()? "#" : "+";
 
-  return str;
+  return san;
 }
 
 
 /// move_from_san() takes a position and a string as input, and tries to
-/// interpret the string as a move in short algebraic notation.  On success,
+/// interpret the string as a move in short algebraic notation. On success,
 /// the move is returned.  On failure (i.e. if the string is unparsable, or
 /// if the move is illegal or ambiguous), MOVE_NONE is returned.
 
-Move move_from_san(Position &pos, const std::string &movestr) {
+Move move_from_san(const Position& pos, const std::string& movestr) {
+
   assert(pos.is_ok());
 
-  MovePicker mp = MovePicker(pos, false, MOVE_NONE, MOVE_NONE, MOVE_NONE,
-                             MOVE_NONE, OnePly);
+  MovePicker mp = MovePicker(pos, false, MOVE_NONE, EmptySearchStack, OnePly);
 
   // Castling moves
-  if(movestr == "O-O-O") {
-    Move m;
-    while((m = mp.get_next_move()) != MOVE_NONE)
-      if(move_is_long_castle(m) && pos.pl_move_is_legal(m))
-        return m;
-    return MOVE_NONE;
-  }
-  else if(movestr == "O-O") {
-    Move m;
-    while((m = mp.get_next_move()) != MOVE_NONE)
-      if(move_is_short_castle(m) && pos.pl_move_is_legal(m))
-        return m;
-    return MOVE_NONE;
-  }
+  if (movestr == "O-O-O" || movestr == "O-O-O+")
+  {
+      Move m;
+      while ((m = mp.get_next_move()) != MOVE_NONE)
+          if (move_is_long_castle(m) && pos.pl_move_is_legal(m))
+              return m;
 
-  // Normal moves
-  const char *cstr = movestr.c_str();
-  const char *c;
-  char *cc;
-  char str[10];
-  int i;
-
-  // Initialize str[] by making a copy of movestr with the characters
-  // 'x', '=', '+' and '#' removed.
-  cc = str;
-  for(i=0, c=cstr; i<10 && *c!='\0' && *c!='\n' && *c!=' '; i++, c++)
-    if(!strchr("x=+#", *c)) {
-      *cc = strchr("nrq", *c)? toupper(*c) : *c;
-      cc++;
-    }
-  *cc = '\0';
-
-  size_t left = 0, right = strlen(str) - 1;
-  PieceType pt = NO_PIECE_TYPE, promotion;
-  Square to;
-  File fromFile = FILE_NONE;
-  Rank fromRank = RANK_NONE;
-
-  // Promotion?
-  if(strchr("BNRQ", str[right])) {
-    promotion = piece_type_from_char(str[right]);
-    right--;
-  }
-  else
-    promotion = NO_PIECE_TYPE;
-
-  // Find the moving piece:
-  if(left < right) {
-    if(strchr("BNRQK", str[left])) {
-      pt = piece_type_from_char(str[left]);
-      left++;
-    }
-    else
-      pt = PAWN;
-  }
-
-  // Find the to square:
-  if(left < right) {
-    if(str[right] < '1' || str[right] > '8' ||
-       str[right-1] < 'a' || str[right-1] > 'h')
       return MOVE_NONE;
-    to = make_square(file_from_char(str[right-1]), rank_from_char(str[right]));
-    right -= 2;
   }
-  else
+  else if (movestr == "O-O" || movestr == "O-O+")
+  {
+      Move m;
+      while ((m = mp.get_next_move()) != MOVE_NONE)
+          if (move_is_short_castle(m) && pos.pl_move_is_legal(m))
+              return m;
+
     return MOVE_NONE;
-
-  // Find the file and/or rank of the from square:
-  if(left <= right) {
-    if(strchr("abcdefgh", str[left])) {
-      fromFile = file_from_char(str[left]);
-      left++;
-    }
-    if(strchr("12345678", str[left]))
-      fromRank = rank_from_char(str[left]);
   }
 
-  // Look for a matching move:
+  // Normal moves. We use a simple FSM to parse the san string.
+  enum { START, TO_FILE, TO_RANK, PROMOTION_OR_CHECK, PROMOTION, CHECK, END };
+  static const std::string pieceLetters = "KQRBN";
+  PieceType pt = NO_PIECE_TYPE, promotion = NO_PIECE_TYPE;
+  File fromFile = FILE_NONE, toFile = FILE_NONE;
+  Rank fromRank = RANK_NONE, toRank = RANK_NONE;
+  Square to;
+  int state = START;
+
+  for (size_t i = 0; i < movestr.length(); i++)
+  {
+      char type, c = movestr[i];
+      if (pieceLetters.find(c) != std::string::npos)
+          type = 'P';
+      else if (c >= 'a' && c <= 'h')
+          type = 'F';
+      else if (c >= '1' && c <= '8')
+          type = 'R';
+      else
+          type = c;
+
+      switch (type) {
+      case 'P':
+          if (state == START)
+          {
+              pt = piece_type_from_char(c);
+              state = TO_FILE;
+          }
+          else if (state == PROMOTION)
+          {
+              promotion = piece_type_from_char(c);
+              state = (i < movestr.length() - 1) ? CHECK : END;
+          }
+          else
+              return MOVE_NONE;
+          break;
+      case 'F':
+          if (state == START)
+          {
+              pt = PAWN;
+              fromFile = toFile = file_from_char(c);
+              state = TO_RANK;
+          }
+          else if (state == TO_FILE)
+          {
+              toFile = file_from_char(c);
+              state = TO_RANK;
+          }
+          else if (state == TO_RANK && toFile != FILE_NONE)
+          {
+              // Previous file was for disambiguation
+              fromFile = toFile;
+              toFile = file_from_char(c);
+          }
+          else
+              return MOVE_NONE;
+          break;
+      case 'R':
+          if (state == TO_RANK)
+          {
+              toRank = rank_from_char(c);
+              state = (i < movestr.length() - 1) ? PROMOTION_OR_CHECK : END;
+          }
+          else if (state == TO_FILE && fromRank == RANK_NONE)
+          {
+              // It's a disambiguation rank instead of a file
+              fromRank = rank_from_char(c);
+          }
+          else
+              return MOVE_NONE;
+          break;
+      case 'x': case 'X':
+          if (state == TO_RANK)
+          {
+              // Previous file was for disambiguation, or it's a pawn capture
+              fromFile = toFile;
+              state = TO_FILE;
+          }
+          else if (state != TO_FILE)
+              return MOVE_NONE;
+          break;
+      case '=':
+          if (state == PROMOTION_OR_CHECK)
+              state = PROMOTION;
+          else
+              return MOVE_NONE;
+          break;
+      case '+': case '#':
+          if (state == PROMOTION_OR_CHECK || state == CHECK)
+              state = END;
+          else
+              return MOVE_NONE;
+          break;
+      default:
+          return MOVE_NONE;
+          break;
+      }
+  }
+
+  if (state != END)
+      return MOVE_NONE;
+
+  // Look for a matching move
   Move m, move = MOVE_NONE;
+  to = make_square(toFile, toRank);
   int matches = 0;
 
-  while((m = mp.get_next_move()) != MOVE_NONE) {
-    bool match = true;
-    if(pos.type_of_piece_on(move_from(m)) != pt)
-      match = false;
-    else if(move_to(m) != to)
-      match = false;
-    else if(move_promotion(m) != promotion)
-      match = false;
-    else if(fromFile != FILE_NONE && fromFile != square_file(move_from(m)))
-      match = false;
-    else if(fromRank != RANK_NONE && fromRank != square_rank(move_from(m)))
-      match = false;
-    if(match) {
-      move = m;
-      matches++;
-    }
-  }
-
-  if(matches == 1)
-    return move;
-  else
-    return MOVE_NONE;
+  while ((m = mp.get_next_move()) != MOVE_NONE)
+      if (   pos.type_of_piece_on(move_from(m)) == pt
+          && move_to(m) == to
+          && move_promotion(m) == promotion
+          && (fromFile == FILE_NONE || fromFile == square_file(move_from(m)))
+          && (fromRank == RANK_NONE || fromRank == square_rank(move_from(m))))
+      {
+          move = m;
+          matches++;
+      }
+  return (matches == 1 ? move : MOVE_NONE);
 }
 
 
@@ -271,34 +288,31 @@ Move move_from_san(Position &pos, const std::string &movestr) {
 /// length of 80 characters.  After a line break, 'startColumn' spaces are
 /// inserted at the beginning of the new line.
 
-const std::string line_to_san(const Position &pos, Move line[], int startColumn,
-                              bool breakLines) {
-  Position p = Position(pos);
+const std::string line_to_san(const Position& pos, Move line[], int startColumn, bool breakLines) {
+
   UndoInfo u;
   std::stringstream s;
   std::string moveStr;
-  size_t length, maxLength;
+  size_t length = 0;
+  size_t maxLength = 80 - startColumn;
+  Position p(pos);
 
-  length = 0;
-  maxLength = 80 - startColumn;
+  for (int i = 0; line[i] != MOVE_NONE; i++)
+  {
+      moveStr = move_to_san(p, line[i]);
+      length += moveStr.length() + 1;
+      if (breakLines && length > maxLength)
+      {
+          s << '\n' << std::setw(startColumn) << ' ';
+          length = moveStr.length() + 1;
+      }
+      s << moveStr << ' ';
 
-  for(int i = 0; line[i] != MOVE_NONE; i++) {
-    moveStr = move_to_san(p, line[i]);
-    length += moveStr.length() + 1;
-    if(breakLines && length > maxLength) {
-      s << "\n";
-      for(int j = 0; j < startColumn; j++)
-        s << " ";
-      length = moveStr.length() + 1;
-    }
-    s << moveStr << " ";
-
-    if(line[i] == MOVE_NULL)
-      p.do_null_move(u);
-    else
-      p.do_move(line[i], u);
+      if (line[i] == MOVE_NULL)
+          p.do_null_move(u);
+      else
+          p.do_move(line[i], u);
   }
-
   return s.str();
 }
 
@@ -307,26 +321,26 @@ const std::string line_to_san(const Position &pos, Move line[], int startColumn,
 /// It is used to write search information to the log file (which is created
 /// when the UCI parameter "Use Search Log" is "true").
 
-const std::string pretty_pv(const Position &pos, int time, int depth,
+const std::string pretty_pv(const Position& pos, int time, int depth,
                             uint64_t nodes, Value score, Move pv[]) {
   std::stringstream s;
 
   // Depth
-  s << std::setw(2) << std::setfill(' ') << depth << "  ";
+  s << std::setw(2) << depth << "  ";
 
   // Score
   s << std::setw(8) << score_string(score);
 
   // Time
-  s << std::setw(8) << std::setfill(' ') << time_string(time) << " ";
+  s << std::setw(8) << time_string(time) << " ";
 
   // Nodes
-  if(nodes < 1000000ULL)
-    s << std::setw(8) << std::setfill(' ') << nodes << " ";
-  else if(nodes < 1000000000ULL)
-    s << std::setw(7) << std::setfill(' ') << nodes/1000ULL << 'k' << " ";
+  if (nodes < 1000000ULL)
+    s << std::setw(8) << nodes << " ";
+  else if (nodes < 1000000000ULL)
+    s << std::setw(7) << nodes/1000ULL << 'k' << " ";
   else
-    s << std::setw(7) << std::setfill(' ') << nodes/1000000ULL << 'M' << " ";
+    s << std::setw(7) << nodes/1000000ULL << 'M' << " ";
 
   // PV
   s << line_to_san(pos, pv, 30, true);
@@ -337,82 +351,80 @@ const std::string pretty_pv(const Position &pos, int time, int depth,
 
 namespace {
 
-  Ambiguity move_ambiguity(Position &pos, Move m) {
-    Square from, to;
-    Piece pc;
+  Ambiguity move_ambiguity(const Position& pos, Move m) {
 
-    from = move_from(m);
-    to = move_to(m);
-    pc = pos.piece_on(from);
+    Square from = move_from(m);
+    Square to = move_to(m);
+    Piece pc = pos.piece_on(from);
 
     // King moves are never ambiguous, because there is never two kings of
     // the same color.
-    if(type_of_piece(pc) == KING)
-      return AMBIGUITY_NONE;
+    if (type_of_piece(pc) == KING)
+        return AMBIGUITY_NONE;
 
-    MovePicker mp = MovePicker(pos, false, MOVE_NONE, MOVE_NONE, MOVE_NONE,
-                               MOVE_NONE, OnePly);
+    MovePicker mp = MovePicker(pos, false, MOVE_NONE, EmptySearchStack, OnePly);
     Move mv, moveList[8];
-    int i, j, n;
 
-    n = 0;
-    while((mv = mp.get_next_move()) != MOVE_NONE)
-      if(move_to(mv) == to && pos.piece_on(move_from(mv)) == pc
-         && pos.pl_move_is_legal(mv))
-        moveList[n++] = mv;
-    if(n == 1)
-      return AMBIGUITY_NONE;
+    int n = 0;
+    while ((mv = mp.get_next_move()) != MOVE_NONE)
+        if (move_to(mv) == to && pos.piece_on(move_from(mv)) == pc && pos.pl_move_is_legal(mv))
+            moveList[n++] = mv;
 
-    j = 0;
-    for(i = 0; i < n; i++)
-      if(square_file(move_from(moveList[i])) == square_file(from))
-        j++;
-    if(j == 1)
-      return AMBIGUITY_FILE;
+    if (n == 1)
+        return AMBIGUITY_NONE;
 
-    j = 0;
-    for(i = 0; i < n; i++)
-      if(square_rank(move_from(moveList[i])) == square_rank(from))
-        j++;
-    if(j == 1)
-      return AMBIGUITY_RANK;
+    int f = 0, r = 0;
+    for (int i = 0; i < n; i++)
+    {
+        if (square_file(move_from(moveList[i])) == square_file(from))
+            f++;
+
+        if (square_rank(move_from(moveList[i])) == square_rank(from))
+            r++;
+    }
+    if (f == 1)
+        return AMBIGUITY_FILE;
+
+    if (r == 1)
+        return AMBIGUITY_RANK;
 
     return AMBIGUITY_BOTH;
   }
 
 
   const std::string time_string(int milliseconds) {
+
     std::stringstream s;
+    s << std::setfill('0');
 
-    int hours = milliseconds / (1000 * 60 * 60);
-    int minutes = (milliseconds - hours*1000*60*60) / (60*1000);
-    int seconds = (milliseconds - hours*1000*60*60 - minutes*60*1000) / 1000;
+    int hours = milliseconds / (1000*60*60);
+    int minutes = (milliseconds - hours*1000*60*60) / (1000*60);
+    int seconds = (milliseconds - hours*1000*60*60 - minutes*1000*60) / 1000;
 
-    if(hours)
-      s << hours << ':';
-    s << std::setw(2) << std::setfill('0') << minutes << ':';
-    s << std::setw(2) << std::setfill('0') << seconds;
+    if (hours)
+        s << hours << ':';
 
+    s << std::setw(2) << minutes << ':' << std::setw(2) << seconds;
     return s.str();
   }
 
 
   const std::string score_string(Value v) {
+
     std::stringstream s;
 
-    if(abs(v) >= VALUE_MATE - 200) {
-      if(v < 0)
-        s << "-#" << (VALUE_MATE + v) / 2;
-      else
+    if (v >= VALUE_MATE - 200)
         s << "#" << (VALUE_MATE - v + 1) / 2;
-    }
-    else {
-      float floatScore = float(v) / float(PawnValueMidgame);
-      if(v >= 0)
-        s << '+';
-      s << std::setprecision(2) << std::fixed << floatScore;
+    else if(v <= -VALUE_MATE + 200)
+        s << "-#" << (VALUE_MATE + v) / 2;
+    else
+    {
+        float floatScore = float(v) / float(PawnValueMidgame);
+        if (v >= 0)
+            s << '+';
+
+        s << std::setprecision(2) << std::fixed << floatScore;
     }
     return s.str();
   }
-
 }

src/san.h

@@ -36,12 +36,9 @@
 //// Prototypes
 ////
 
-extern const std::string move_to_san(Position &pos, Move m);
-extern Move move_from_san(Position &pos, const std::string &str);
-extern const std::string line_to_san(const Position &pos, Move line[],
-                                     int startColumn, bool breakLines);
-extern const std::string pretty_pv(const Position &pos, int time, int depth,
-                                   uint64_t nodes, Value score, Move pv[]);
-
+extern const std::string move_to_san(const Position& pos, Move m);
+extern Move move_from_san(const Position& pos, const std::string& str);
+extern const std::string line_to_san(const Position& pos, Move line[], int startColumn, bool breakLines);
+extern const std::string pretty_pv(const Position& pos, int time, int depth, uint64_t nodes, Value score, Move pv[]);
 
 #endif // !defined(SAN_H_INCLUDED)

src/search.h

@@ -25,7 +25,6 @@
 //// Includes
 ////
 
-#include "types.h"
 #include "depth.h"
 #include "history.h"
 #include "lock.h"
@@ -41,6 +40,7 @@
 
 const int PLY_MAX = 100;
 const int PLY_MAX_PLUS_2 = 102;
+const int KILLER_MAX = 2;
 
 
 ////
@@ -56,8 +56,9 @@ struct SearchStack {
   Move pv[PLY_MAX];
   Move currentMove;
   Value currentMoveCaptureValue;
-  Move mateKiller, killer1, killer2;
+  Move mateKiller;
   Move threatMove;
+  Move killers[KILLER_MAX];
   Depth reduction;
 };
 
@@ -66,10 +67,9 @@ struct SearchStack {
 //// Global variables
 ////
 
+extern SearchStack EmptySearchStack;
 extern TranspositionTable TT;
-
 extern int ActiveThreads;
-
 extern Lock SMPLock;
 
 // Perhaps better to make H local, and pass as parameter to MovePicker?

src/tt.cpp

@@ -108,29 +108,25 @@ void TranspositionTable::store(const Position &pos, Value v, Depth d,
   TTEntry *tte, *replace;
 
   tte = replace = first_entry(pos);
-  for (int i = 0; i < 4; i++)
+  for (int i = 0; i < 4; i++, tte++)
   {
-    if (!(tte+i)->key()) // still empty
-    {
-        *(tte+i) = TTEntry(pos.get_key(), v, type, d, m, generation);
-        writes++;
-        return;
-    }
-    if ((tte+i)->key() == pos.get_key()) // overwrite old
+    if (!tte->key() || tte->key() == pos.get_key()) // empty or overwrite old
     {
         if (m == MOVE_NONE)
-            m = (tte+i)->move();
+            m = tte->move();
 
-        *(tte+i) = TTEntry(pos.get_key(), v, type, d, m, generation);
+        *tte = TTEntry(pos.get_key(), v, type, d, m, generation);
         return;
     }
-    if (   i == 0  // already is (replace == tte+i), common case
-        || replace->generation() < (tte+i)->generation())
+    else if (i == 0)  // replace would be a no-op in this common case
         continue;
 
-    if (    replace->generation() > (tte+i)->generation()
-        || (tte+i)->depth() < replace->depth())
-        replace = tte+i;
+    int c1 = (replace->generation() == generation ?  2 : 0);
+    int c2 = (tte->generation() == generation ? -2 : 0);
+    int c3 = (tte->depth() < replace->depth() ?  1 : 0);
+
+    if (c1 + c2 + c3 > 0)
+        replace = tte;
   }
   *replace = TTEntry(pos.get_key(), v, type, d, m, generation);
   writes++;

src/ucioption.cpp

@@ -85,6 +85,7 @@ namespace {
     o.push_back(Option("Pawn Structure (Endgame)", 100, 0, 200));
     o.push_back(Option("Passed Pawns (Middle Game)", 100, 0, 200));
     o.push_back(Option("Passed Pawns (Endgame)", 100, 0, 200));
+    o.push_back(Option("Space", 100, 0, 200));
     o.push_back(Option("Aggressiveness", 100, 0, 200));
     o.push_back(Option("Cowardice", 100, 0, 200));
     o.push_back(Option("King Safety Curve", "Quadratic", COMBO));
@@ -96,8 +97,7 @@ namespace {
     o.push_back(Option("King Safety X Intercept", 0, 0, 20));
     o.push_back(Option("King Safety Max Slope", 30, 10, 100));
     o.push_back(Option("King Safety Max Value", 500, 100, 1000));
-    o.push_back(Option("Queen Contact Check Bonus", 4, 0, 8));
-    o.push_back(Option("Rook Contact Check Bonus", 2, 0, 4));
+    o.push_back(Option("Queen Contact Check Bonus", 3, 0, 8));
     o.push_back(Option("Queen Check Bonus", 2, 0, 4));
     o.push_back(Option("Rook Check Bonus", 1, 0, 4));
     o.push_back(Option("Bishop Check Bonus", 1, 0, 4));
@@ -120,11 +120,11 @@ namespace {
     o.push_back(Option("Full Depth Moves (non-PV nodes)", 3, 1, 100));
     o.push_back(Option("Threat Depth", 5, 0, 100));
     o.push_back(Option("Selective Plies", 7, 0, 10));
+    o.push_back(Option("Null driven IID", false));
     o.push_back(Option("Futility Pruning (Main Search)", true));
     o.push_back(Option("Futility Pruning (Quiescence Search)", true));
-    o.push_back(Option("Futility Margin 0", 50, 0, 1000));
-    o.push_back(Option("Futility Margin 1", 100, 0, 1000));
-    o.push_back(Option("Futility Margin 2", 300, 0, 1000));
+    o.push_back(Option("Futility Margin (Quiescence Search)", 50, 0, 1000));
+    o.push_back(Option("Futility Margin Scale Factor (Main Search)", 100, 0, 1000));
     o.push_back(Option("Maximum Razoring Depth", 3, 0, 4));
     o.push_back(Option("Razoring Margin", 300, 150, 600));
     o.push_back(Option("LSN filtering", false));
@@ -176,14 +176,16 @@ namespace {
   template<typename T>
   T get_option_value(const std::string& optionName) {
 
-      T ret;
+      T ret = T();
       Options::iterator it = option_with_name(optionName);
 
       if (it != options.end())
       {
           std::istringstream ss(it->currentValue);
           ss >> ret;
-      }
+      } else
+          assert(false);
+
       return ret;
   }