Bonus for pawn scrifice which create passed pawn

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 6c9a29d7034408df7e750baa3f1b7e2b824d0cde..95d5fb4cfeb5af4da52552430224b3622470d3cc 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -32,10 +32,10 @@ namespace {
   #define S(mg, eg) make_score(mg, eg)
 
   // Isolated pawn penalty by opposed flag
-  const Score Isolated[2] = { S(45, 40), S(30, 27) };
+  const Score Isolated[] = { S(45, 40), S(30, 27) };
 
   // Backward pawn penalty by opposed flag
-  const Score Backward[2] = { S(56, 33), S(41, 19) };
+  const Score Backward[] = { S(56, 33), S(41, 19) };
 
   // Unsupported pawn penalty for pawns which are neither isolated or backward
   const Score Unsupported = S(17, 8);
@@ -44,7 +44,7 @@ namespace {
   Score Connected[2][2][2][RANK_NB];
 
   // Doubled pawn penalty
-  const Score Doubled = S(18,38);
+  const Score Doubled = S(18, 38);
 
   // Lever bonus by rank
   const Score Lever[RANK_NB] = {
@@ -53,7 +53,7 @@ namespace {
   };
 
   // Weakness of our pawn shelter in front of the king by [distance from edge][rank].
-  // RANK_1 = 0 is used for files where we have no pawns, or where our pawn is behind our king.
+  // RANK_1 = 0 is used for files where we have no pawns or our pawn is behind our king.
   const Value ShelterWeakness[][RANK_NB] = {
     { V(100), V(20), V(10), V(46), V(82), V( 86), V( 98) },
     { V(116), V( 4), V(28), V(87), V(94), V(108), V(104) },
@@ -63,7 +63,7 @@ namespace {
 
   // Danger of enemy pawns moving toward our king by [type][distance from edge][rank].
   // For the unopposed and unblocked cases, RANK_1 = 0 is used when opponent has no pawn
-  // on the given file, or his pawn his behind our king.
+  // on the given file, or their pawn is behind our king.
   const Value StormDanger[][4][RANK_NB] = {
     { { V( 0),  V(-290), V(-274), V(57), V(41) },  //BlockedByKing
       { V( 0),  V(  60), V( 144), V(39), V(13) },
@@ -99,11 +99,11 @@ namespace {
     const Square Left  = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
 
     Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
+    Bitboard lever, leverPush, connected;
     Square s;
-    bool opposed, lever, connected, backward;
+    bool opposed, backward;
     Score score = SCORE_ZERO;
     const Square* pl = pos.squares<PAWN>(Us);
-    const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
 
     Bitboard ourPawns   = pos.pieces(Us  , PAWN);
     Bitboard theirPawns = pos.pieces(Them, PAWN);
@@ -128,8 +128,9 @@ namespace {
         // Flag the pawn
         opposed    = theirPawns & forward_bb(Us, s);
         stoppers   = theirPawns & passed_pawn_mask(Us, s);
-        lever      = theirPawns & pawnAttacksBB[s];
-        doubled    = ourPawns   & (s + Up);
+        lever      = theirPawns & PawnAttacks[Us][s];
+        leverPush  = theirPawns & PawnAttacks[Us][s + Up];
+        doubled    = ourPawns   & (s - Up);
         neighbours = ourPawns   & adjacent_files_bb(f);
         phalanx    = neighbours & rank_bb(s);
         supported  = neighbours & rank_bb(s - Up);
@@ -153,10 +154,22 @@ namespace {
         }
 
         // Passed pawns will be properly scored in evaluation because we need
-        // full attack info to evaluate them.
-        if (!stoppers && !(ourPawns & forward_bb(Us, s)))
+        // full attack info to evaluate them. Include also not passed pawns
+        // which could become passed after one or two pawn pushes when are
+        // not attacked more times than defended.
+        if (   !(stoppers ^ lever ^ leverPush)
+            && !(ourPawns & forward_bb(Us, s))
+            && popcount(supported) >= popcount(lever)
+            && popcount(phalanx)   >= popcount(leverPush))
             e->passedPawns[Us] |= s;
 
+        else if (    stoppers == SquareBB[s + Up]
+                 &&  relative_rank(Us, s) >= RANK_5
+                 && (b = (shift<Up>(supported) & ~theirPawns)))
+            while(b)
+                if(!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
+                    e->passedPawns[Us] |= s;
+
         // Score this pawn
         if (!neighbours)
             score -= Isolated[opposed];
@@ -170,8 +183,8 @@ namespace {
         if (connected)
             score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];
 
-        if (doubled)
-            score -= Doubled;
+        if (doubled && !supported)
+           score -= Doubled;
 
         if (lever)
             score += Lever[relative_rank(Us, s)];
@@ -249,12 +262,13 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) {
       b  = theirPawns & file_bb(f);
       Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
 
-      safety -=  ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
+      int d = std::min(f, FILE_H - f);
+      safety -=  ShelterWeakness[d][rkUs]
                + StormDanger
                  [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing  :
                   rkUs   == RANK_1                                          ? Unopposed :
                   rkThem == rkUs + 1                                        ? BlockedByPawn  : Unblocked]
-                 [std::min(f, FILE_H - f)][rkThem];
+                 [d][rkThem];
   }
 
   return safety;