X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=c6d390b32efb0ea9e9a22276605a0c688485a0ae;hp=294ebe081fecfda5b7d36a01133b65ba0e276f86;hb=fc89dbcab2616603ba6edbf6277c3edecfc3a64a;hpb=9fc602bae74b8e09bd45ace3b42a8ce84d56b23c

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 294ebe08..c6d390b3 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -70,6 +70,10 @@ namespace {
     S(34,68), S(83,166), S(0, 0), S( 0, 0)
   };
 
+  // UnpairedPawnsTable[] gives a score according to the number
+  // of panws that do not have an enemy pawn in front of them.
+  const int UnpairedPawnsTable[8] = { 32, 48, 64, 80, 96, 112, 128, 128 };
+
   // Pawn storm tables for positions with opposite castling
   const int QStormTable[64] = {
     0,  0,  0,  0, 0, 0, 0, 0,
@@ -183,10 +187,11 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
   Square s;
   File f;
   Rank r;
-  bool passed, isolated, doubled, chain, backward, candidate;
+  bool passed, isolated, doubled, opposed, chain, backward, candidate;
   int bonus;
   Score value = make_score(0, 0);
   const Square* ptr = pos.piece_list_begin(Us, PAWN);
+  int unpairedPawnsNum = pos.piece_count(Us, PAWN);
 
   // Initialize pawn storm scores by giving bonuses for open files
   for (f = FILE_A; f <= FILE_H; f++)
@@ -206,9 +211,14 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
       assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN));
 
       // Passed, isolated or doubled pawn?
-      passed   = Position::pawn_is_passed(theirPawns, Us, s);
-      isolated = Position::pawn_is_isolated(ourPawns, s);
-      doubled  = Position::pawn_is_doubled(ourPawns, Us, s);
+      passed   = !(theirPawns & passed_pawn_mask(Us, s));
+      isolated = !(ourPawns & neighboring_files_bb(s));
+      doubled  = ourPawns & squares_behind(Us, s);
+      opposed  = theirPawns & squares_in_front_of(Us, s);
+
+      // Decrease number of unpaired pawns
+      if (opposed)
+          unpairedPawnsNum--;
 
       // We calculate kingside and queenside pawn storm
       // scores for both colors. These are used when evaluating
@@ -226,21 +236,16 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
           Bitboard b = outpost_mask(Us, s) & theirPawns & (FileFBB | FileGBB | FileHBB);
           while (b)
           {
+              // Give a bonus according to the distance of the nearest enemy pawn
               Square s2 = pop_1st_bit(&b);
+              int v = StormLeverBonus[f] - 2 * square_distance(s, s2);
+
+              // If enemy pawn has no pawn beside itself is particularly vulnerable.
+              // Big bonus, especially against a weakness on the rook file
               if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
-              {
-                  // The enemy pawn has no pawn beside itself, which makes it
-                  // particularly vulnerable. Big bonus, especially against a
-                  // weakness on the rook file.
-                  if (square_file(s2) == FILE_H)
-                      bonus += 4*StormLeverBonus[f] - 8*square_distance(s, s2);
-                  else
-                      bonus += 2*StormLeverBonus[f] - 4*square_distance(s, s2);
-              } else
-                  // There is at least one enemy pawn beside the enemy pawn we look
-                  // at, which means that the pawn has somewhat better chances of
-                  // defending itself by advancing. Smaller bonus.
-                  bonus += StormLeverBonus[f] - 2*square_distance(s, s2);
+                  v *= (square_file(s2) == FILE_H ? 4 : 2);
+
+              bonus += v;
           }
       }
       pi->ksStormValue[Us] += bonus;
@@ -252,21 +257,16 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
           Bitboard b = outpost_mask(Us, s) & theirPawns & (FileABB | FileBBB | FileCBB);
           while (b)
           {
+              // Give a bonus according to the distance of the nearest enemy pawn
               Square s2 = pop_1st_bit(&b);
+              int v = StormLeverBonus[f] - 4 * square_distance(s, s2);
+
+              // If enemy pawn has no pawn beside itself is particularly vulnerable.
+              // Big bonus, especially against a weakness on the rook file
               if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
-              {
-                  // The enemy pawn has no pawn beside itself, which makes it
-                  // particularly vulnerable. Big bonus, especially against a
-                  // weakness on the rook file.
-                  if (square_file(s2) == FILE_A)
-                      bonus += 4*StormLeverBonus[f] - 16*square_distance(s, s2);
-                  else
-                      bonus += 2*StormLeverBonus[f] - 8*square_distance(s, s2);
-              } else
-                  // There is at least one enemy pawn beside the enemy pawn we look
-                  // at, which means that the pawn has somewhat better chances of
-                  // defending itself by advancing. Smaller bonus.
-                  bonus += StormLeverBonus[f] - 4*square_distance(s, s2);
+                  v *= (square_file(s2) == FILE_A ? 4 : 2);
+
+              bonus += v;
           }
       }
       pi->qsStormValue[Us] += bonus;
@@ -309,7 +309,7 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
 
       // Test for candidate passed pawn
       candidate =   !passed
-                 && !(theirPawns & file_bb(f))
+                 && !opposed
                  && (  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);
@@ -346,6 +346,9 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
           value += CandidateBonus[relative_rank(Us, s)];
   }
 
+  // Calculate a scale factor to be used to evaluate if position is drawish
+  pi->factor[Us] = UnpairedPawnsTable[unpairedPawnsNum];
+
   return value;
 }