Allow for higher depths. (#2147)

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index c9c9e5992dbaf83cca00876317e3c3d9456647a1..0a88c9f1ba37b07a3738800fea6d11f0c003ec09 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -18,6 +18,7 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <algorithm>
 #include <cassert>
 
 #include "bitboard.h"
@@ -35,8 +36,8 @@ namespace {
   constexpr Score Doubled  = S(11, 56);
   constexpr Score Isolated = S( 5, 15);
 
-  // Connected pawn bonus by opposed, phalanx, #support and rank
-  Score Connected[2][2][3][RANK_NB];
+  // Connected pawn bonus
+  constexpr int Connected[RANK_NB] = { 0, 13, 17, 24, 59, 96, 171 };
 
   // Strength of pawn shelter for our king by [distance from edge][rank].
   // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king.
@@ -77,11 +78,8 @@ namespace {
     Bitboard theirPawns = pos.pieces(Them, PAWN);
 
     e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
-    e->semiopenFiles[Us] = 0xFF;
     e->kingSquares[Us]   = SQ_NONE;
     e->pawnAttacks[Us]   = pawn_attacks_bb<Us>(ourPawns);
-    e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
-    e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
 
     // Loop through all pawns of the current color and score each pawn
     while ((s = *pl++) != SQ_NONE)
@@ -89,8 +87,8 @@ namespace {
         assert(pos.piece_on(s) == make_piece(Us, PAWN));
 
         File f = file_of(s);
+        Rank r = relative_rank(Us, s);
 
-        e->semiopenFiles[Us]   &= ~(1 << f);
         e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
 
         // Flag the pawn
@@ -117,8 +115,7 @@ namespace {
             && popcount(phalanx) >= popcount(leverPush))
             e->passedPawns[Us] |= s;
 
-        else if (   stoppers == square_bb(s + Up)
-                 && relative_rank(Us, s) >= RANK_5)
+        else if (stoppers == square_bb(s + Up) && r >= RANK_5)
         {
             b = shift<Up>(support) & ~theirPawns;
             while (b)
@@ -128,8 +125,11 @@ namespace {
 
         // Score this pawn
         if (support | phalanx)
-            score += Connected[opposed][bool(phalanx)][popcount(support)][relative_rank(Us, s)];
-
+        {
+            int v = (phalanx ? 3 : 2) * Connected[r];
+            v = 17 * popcount(support) + (v >> (opposed + 1));
+            score += make_score(v, v * (r - 2) / 4);
+        }
         else if (!neighbours)
             score -= Isolated, e->weakUnopposed[Us] += !opposed;
 
@@ -147,27 +147,6 @@ namespace {
 
 namespace Pawns {
 
-/// Pawns::init() initializes some tables needed by evaluation. Instead of using
-/// hard-coded tables, when makes sense, we prefer to calculate them with a formula
-/// to reduce independent parameters and to allow easier tuning and better insight.
-
-void init() {
-
-  static constexpr int Seed[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 };
-
-  for (int opposed = 0; opposed <= 1; ++opposed)
-      for (int phalanx = 0; phalanx <= 1; ++phalanx)
-          for (int support = 0; support <= 2; ++support)
-              for (Rank r = RANK_2; r < RANK_8; ++r)
-  {
-      int v = 17 * support;
-      v += (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
-
-      Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4);
-  }
-}
-
-
 /// Pawns::probe() looks up the current position's pawns configuration in
 /// the pawns hash table. It returns a pointer to the Entry if the position
 /// is found. Otherwise a new Entry is computed and stored there, so we don't
@@ -184,7 +163,6 @@ Entry* probe(const Position& pos) {
   e->key = key;
   e->scores[WHITE] = evaluate<WHITE>(pos, e);
   e->scores[BLACK] = evaluate<BLACK>(pos, e);
-  e->passedCount= popcount(e->passedPawns[WHITE] | e->passedPawns[BLACK]);
 
   return e;
 }
@@ -198,14 +176,14 @@ Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
 
   constexpr Color     Them = (Us == WHITE ? BLACK : WHITE);
   constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
-  constexpr Bitboard  BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
+  constexpr Bitboard BlockSquares =  (Rank1BB | Rank2BB | Rank7BB | Rank8BB)
+                                   & (FileABB | FileHBB);
 
   Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
   Bitboard ourPawns = b & pos.pieces(Us);
   Bitboard theirPawns = b & pos.pieces(Them);
 
-  Value safety = (shift<Down>(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) ?
-                 Value(374) : Value(5);
+  Value safety = (shift<Down>(theirPawns) & BlockSquares & ksq) ? Value(374) : Value(5);
 
   File center = clamp(file_of(ksq), FILE_B, FILE_G);
   for (File f = File(center - 1); f <= File(center + 1); ++f)
@@ -235,11 +213,15 @@ Score Entry::do_king_safety(const Position& pos) {
   Square ksq = pos.square<KING>(Us);
   kingSquares[Us] = ksq;
   castlingRights[Us] = pos.castling_rights(Us);
-  int minKingPawnDistance = 0;
 
   Bitboard pawns = pos.pieces(Us, PAWN);
-  if (pawns)
-      while (!(DistanceRingBB[ksq][++minKingPawnDistance] & pawns)) {}
+  int minPawnDist = pawns ? 8 : 0;
+
+  if (pawns & PseudoAttacks[KING][ksq])
+      minPawnDist = 1;
+
+  else while (pawns)
+      minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
 
   Value bonus = evaluate_shelter<Us>(pos, ksq);
 
@@ -250,7 +232,7 @@ Score Entry::do_king_safety(const Position& pos) {
   if (pos.can_castle(Us | QUEEN_SIDE))
       bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)));
 
-  return make_score(bonus, -16 * minKingPawnDistance);
+  return make_score(bonus, -16 * minPawnDist);
 }
 
 // Explicit template instantiation