Speedup and simplify pinners and blockers

To compute dicovered check or pinned pieces we use some bitwise
operators that are not really needed because already accounted for
at the caller site.

For instance in evaluation we compute:

     pos.pinned_pieces(Us) & s

Where pinned_pieces() is:

     st->blockersForKing[c] & pieces(c)

So in this case the & operator with pieces(c) is useless,
given the outer '& s'.

There are many places where we can use the naked blockersForKing[]
instead of the full pinned_pieces() or discovered_check_candidates().

This path is simpler than original and gives around 1% speed up for me.
Also tested for speed by mstembera and snicolet (neutral in both cases).

No functional change.

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 884b1d854722939f90412be2805a98d4d378461d..11a6fa27db5ff24504d0a08ad9adc3f233318f98 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -306,7 +306,7 @@ namespace {
           : Pt ==   ROOK ? attacks_bb<  ROOK>(s, pos.pieces() ^ pos.pieces(QUEEN) ^ pos.pieces(Us, ROOK))
                          : pos.attacks_from<Pt>(s);
 
-        if (pos.pinned_pieces(Us) & s)
+        if (pos.blockers_for_king(Us) & s)
             b &= LineBB[pos.square<KING>(Us)][s];
 
         attackedBy2[Us] |= attackedBy[Us][ALL_PIECES] & b;
@@ -392,8 +392,8 @@ namespace {
         if (Pt == QUEEN)
         {
             // Penalty if any relative pin or discovered attack against the queen
-            Bitboard pinners;
-            if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, pinners))
+            Bitboard queenPinners;
+            if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, queenPinners))
                 score -= WeakQueen;
         }
     }
@@ -413,7 +413,7 @@ namespace {
                                        : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
 
     const Square ksq = pos.square<KING>(Us);
-    Bitboard weak, b, b1, b2, safe, unsafeChecks;
+    Bitboard weak, b, b1, b2, safe, unsafeChecks, pinned;
 
     // King shelter and enemy pawns storm
     Score score = pe->king_safety<Us>(pos, ksq);
@@ -464,11 +464,12 @@ namespace {
         // Unsafe or occupied checking squares will also be considered, as long as
         // the square is in the attacker's mobility area.
         unsafeChecks &= mobilityArea[Them];
+        pinned = pos.blockers_for_king(Us) & pos.pieces(Us);
 
         kingDanger +=        kingAttackersCount[Them] * kingAttackersWeight[Them]
                      + 102 * kingAdjacentZoneAttacksCount[Them]
                      + 191 * popcount(kingRing[Us] & weak)
-                     + 143 * popcount(pos.pinned_pieces(Us) | unsafeChecks)
+                     + 143 * popcount(pinned | unsafeChecks)
                      - 848 * !pos.count<QUEEN>(Them)
                      -   9 * mg_value(score) / 8
                      +  40;

diff --git a/src/movegen.cpp b/src/movegen.cpp
index 14f30ea00c01b761748ebb54d284c3e3ba0e8c43..cb221d95e178e1833c00fb414e183561b02a9924 100644 (file)
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -135,7 +135,7 @@ namespace {
             // if the pawn is not on the same file as the enemy king, because we
             // don't generate captures. Note that a possible discovery check
             // promotion has been already generated amongst the captures.
-            Bitboard dcCandidates = pos.discovered_check_candidates();
+            Bitboard dcCandidates = pos.blockers_for_king(Them);
             if (pawnsNotOn7 & dcCandidates)
             {
                 Bitboard dc1 = shift<Up>(pawnsNotOn7 & dcCandidates) & emptySquares & ~file_bb(ksq);
@@ -241,7 +241,7 @@ namespace {
                 && !(PseudoAttacks[Pt][from] & target & pos.check_squares(Pt)))
                 continue;
 
-            if (pos.discovered_check_candidates() & from)
+            if (pos.blockers_for_king(~us) & from)
                 continue;
         }
 
@@ -336,7 +336,7 @@ ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
   assert(!pos.checkers());
 
   Color us = pos.side_to_move();
-  Bitboard dc = pos.discovered_check_candidates();
+  Bitboard dc = pos.blockers_for_king(~us) & pos.pieces(us);
 
   while (dc)
   {
@@ -403,8 +403,9 @@ ExtMove* generate<EVASIONS>(const Position& pos, ExtMove* moveList) {
 template<>
 ExtMove* generate<LEGAL>(const Position& pos, ExtMove* moveList) {
 
-  Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
-  Square ksq = pos.square<KING>(pos.side_to_move());
+  Color us = pos.side_to_move();
+  Bitboard pinned = pos.blockers_for_king(us) & pos.pieces(us);
+  Square ksq = pos.square<KING>(us);
   ExtMove* cur = moveList;
 
   moveList = pos.checkers() ? generate<EVASIONS    >(pos, moveList)

diff --git a/src/position.cpp b/src/position.cpp
index fdae0ae0bf211999f9c2ee69472c4f151af0f8a0..d48ec18cb0d69aead115584573e135d468a9ea06 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -464,7 +464,7 @@ const string Position::fen() const {
 
 Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const {
 
-  Bitboard result = 0;
+  Bitboard blockers = 0;
   pinners = 0;
 
   // Snipers are sliders that attack 's' when a piece is removed
@@ -476,14 +476,14 @@ Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners
     Square sniperSq = pop_lsb(&snipers);
     Bitboard b = between_bb(s, sniperSq) & pieces();
 
-    if (!more_than_one(b))
+    if (b && !more_than_one(b))
     {
-        result |= b;
+        blockers |= b;
         if (b & pieces(color_of(piece_on(s))))
             pinners |= sniperSq;
     }
   }
-  return result;
+  return blockers;
 }
 
 
@@ -540,7 +540,7 @@ bool Position::legal(Move m) const {
 
   // A non-king move is legal if and only if it is not pinned or it
   // is moving along the ray towards or away from the king.
-  return   !(pinned_pieces(us) & from)
+  return   !(blockers_for_king(us) & from)
         ||  aligned(from, to_sq(m), square<KING>(us));
 }
 
@@ -632,7 +632,7 @@ bool Position::gives_check(Move m) const {
       return true;
 
   // Is there a discovered check?
-  if (   (discovered_check_candidates() & from)
+  if (   (st->blockersForKing[~sideToMove] & from)
       && !aligned(from, to, square<KING>(~sideToMove)))
       return true;
 

diff --git a/src/position.h b/src/position.h
index 34e2f7eef16d0fdb9df11f043087801f3b33aa3d..18c783f0836ecd6b0d92157ae731472d5040f6ea 100644 (file)
--- a/src/position.h
+++ b/src/position.h
@@ -105,8 +105,7 @@ public:
 
   // Checking
   Bitboard checkers() const;
-  Bitboard discovered_check_candidates() const;
-  Bitboard pinned_pieces(Color c) const;
+  Bitboard blockers_for_king(Color c) const;
   Bitboard check_squares(PieceType pt) const;
 
   // Attacks to/from a given square
@@ -296,12 +295,8 @@ inline Bitboard Position::checkers() const {
   return st->checkersBB;
 }
 
-inline Bitboard Position::discovered_check_candidates() const {
-  return st->blockersForKing[~sideToMove] & pieces(sideToMove);
-}
-
-inline Bitboard Position::pinned_pieces(Color c) const {
-  return st->blockersForKing[c] & pieces(c);
+inline Bitboard Position::blockers_for_king(Color c) const {
+  return st->blockersForKing[c];
 }
 
 inline Bitboard Position::check_squares(PieceType pt) const {

diff --git a/src/search.cpp b/src/search.cpp
index ca5a107ea2853df9b3648eeb3f4e56bb23c039b6..394f228fb4f59956914ab3d014b199934d245716 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -108,6 +108,13 @@ namespace {
   void update_quiet_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, int bonus);
   void update_capture_stats(const Position& pos, Move move, Move* captures, int captureCnt, int bonus);
 
+  inline bool gives_check(const Position& pos, Move move) {
+    Color us = pos.side_to_move();
+    return  type_of(move) == NORMAL && !(pos.blockers_for_king(~us) & pos.pieces(us))
+          ? pos.check_squares(type_of(pos.moved_piece(move))) & to_sq(move)
+          : pos.gives_check(move);
+  }
+
   // perft() is our utility to verify move generation. All the leaf nodes up
   // to the given depth are generated and counted, and the sum is returned.
   template<bool Root>
@@ -823,10 +830,7 @@ moves_loop: // When in check, search starts from here
       extension = DEPTH_ZERO;
       captureOrPromotion = pos.capture_or_promotion(move);
       movedPiece = pos.moved_piece(move);
-
-      givesCheck =  type_of(move) == NORMAL && !pos.discovered_check_candidates()
-                  ? pos.check_squares(type_of(movedPiece)) & to_sq(move)
-                  : pos.gives_check(move);
+      givesCheck = gives_check(pos, move);
 
       moveCountPruning =   depth < 16 * ONE_PLY
                         && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
@@ -1238,9 +1242,7 @@ moves_loop: // When in check, search starts from here
     {
       assert(is_ok(move));
 
-      givesCheck =  type_of(move) == NORMAL && !pos.discovered_check_candidates()
-                  ? pos.check_squares(type_of(pos.moved_piece(move))) & to_sq(move)
-                  : pos.gives_check(move);
+      givesCheck = gives_check(pos, move);
 
       moveCount++;