Add lsb() overload

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 4ca1bb0efcc71c58013a1d124472d383e4254990..fece246b1c999a31611a8b8661b4e97d8e9520e2 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -17,6 +17,7 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <algorithm>
 #include <cassert>
 
 #include "bitboard.h"
@@ -62,15 +63,16 @@ namespace {
     S(34,68), S(83,166), S(0, 0), S( 0, 0)
   };
 
-  // Weakness of our pawn shelter in front of the king indexed by [king pawn][rank]
-  const Value ShelterWeakness[2][RANK_NB] =
-  { { V(141), V(0), V(38), V(102), V(128), V(141), V(141) },
-    { V( 61), V(0), V(16), V( 44), V( 56), V( 61), V( 61) } };
+  // Weakness of our pawn shelter in front of the king indexed by [rank]
+  const Value ShelterWeakness[RANK_NB] =
+  { V(100), V(0), V(27), V(73), V(92), V(101), V(101) };
 
-  // Danger of enemy pawns moving toward our king indexed by [pawn blocked][rank]
-  const Value StormDanger[2][RANK_NB] =
-  { { V(26), V(0), V(128), V(51), V(26) },
-    { V(13), V(0), V( 64), V(25), V(13) } };
+  // Danger of enemy pawns moving toward our king indexed by
+  // [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn]
+  const Value StormDanger[3][RANK_NB] = {
+  { V( 0),  V(64), V(128), V(51), V(26) },
+  { V(26),  V(32), V( 96), V(38), V(20) },
+  { V( 0),  V( 0), V( 64), V(25), V(13) }};
 
   // Max bonus for king safety. Corresponds to start position with all the pawns
   // in front of the king and no enemy pawn on the horizont.
@@ -90,7 +92,6 @@ namespace {
     Bitboard b;
     Square s;
     File f;
-    Rank r;
     bool passed, isolated, doubled, opposed, chain, backward, candidate;
     Score value = SCORE_ZERO;
     const Square* pl = pos.list<PAWN>(Us);
@@ -102,7 +103,7 @@ namespace {
     e->kingSquares[Us] = SQ_NONE;
     e->semiopenFiles[Us] = 0xFF;
     e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
-    e->pawnsOnSquares[Us][BLACK] = popcount<Max15>(ourPawns & BlackSquares);
+    e->pawnsOnSquares[Us][BLACK] = popcount<Max15>(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
@@ -111,13 +112,12 @@ namespace {
         assert(pos.piece_on(s) == make_piece(Us, PAWN));
 
         f = file_of(s);
-        r = rank_of(s);
 
         // This file cannot be semi-open
         e->semiopenFiles[Us] &= ~(1 << f);
 
         // Our rank plus previous one. Used for chain detection
-        b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
+        b = rank_bb(s) | rank_bb(s - pawn_push(Us));
 
         // Flag the pawn as passed, isolated, doubled or member of a pawn
         // chain (but not the backward one).
@@ -127,15 +127,15 @@ namespace {
         opposed  =   theirPawns & forward_bb(Us, s);
         passed   = !(theirPawns & passed_pawn_mask(Us, s));
 
-        // Test for backward pawn
-        backward = false;
-
+        // Test for backward pawn.
         // If the pawn is passed, isolated, or member of a pawn chain it cannot
         // be backward. If there are friendly pawns behind on adjacent files
         // or if can capture an enemy pawn it cannot be backward either.
-        if (   !(passed | isolated | chain)
-            && !(ourPawns & pawn_attack_span(Them, s))
-            && !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
+        if (   (passed | isolated | chain)
+            || (ourPawns & pawn_attack_span(Them, s))
+            || (pos.attacks_from<PAWN>(s, Us) & theirPawns))
+            backward = false;
+        else
         {
             // We now know that there are no friendly pawns beside or behind this
             // pawn on adjacent files. We now check whether the pawn is
@@ -221,24 +221,20 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) {
 
   Value safety = MaxSafetyBonus;
   Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
-  Bitboard ourPawns = b & pos.pieces(Us) & ~rank_bb(ksq);
+  Bitboard ourPawns = b & pos.pieces(Us);
   Bitboard theirPawns = b & pos.pieces(Them);
   Rank rkUs, rkThem;
-  File kf = file_of(ksq);
-
-  kf = (kf == FILE_A) ? FILE_B : (kf == FILE_H) ? FILE_G : kf;
+  File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
 
   for (int f = kf - 1; f <= kf + 1; f++)
   {
-      // Shelter penalty is higher for the pawn in front of the king
       b = ourPawns & FileBB[f];
-      rkUs = b ? rank_of(Us == WHITE ? lsb(b) : ~msb(b)) : RANK_1;
-      safety -= ShelterWeakness[f != kf][rkUs];
+      rkUs = b ? relative_rank(Us, lsb(Us, b)) : RANK_1;
+      safety -= ShelterWeakness[rkUs];
 
-      // Storm danger is smaller if enemy pawn is blocked
       b  = theirPawns & FileBB[f];
-      rkThem = b ? rank_of(Us == WHITE ? lsb(b) : ~msb(b)) : RANK_1;
-      safety -= StormDanger[rkThem == rkUs + 1][rkThem];
+      rkThem = b ? relative_rank(Us, lsb(Us, b)) : RANK_1;
+      safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
   }
 
   return safety;