X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fmovegen.cpp;h=be16845095d43e04f317f33541f0b6a56761957a;hb=a0e2debe3f1d14f84984a9a2c1482dc41f695548;hp=c3c149b700b697a507667c0f7db40502263a1815;hpb=79bb28281ce5e9b40b2662915a96e9072ddad82e;p=stockfish

diff --git a/src/movegen.cpp b/src/movegen.cpp
index c3c149b7..be168450 100644
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -58,19 +58,16 @@ namespace {
     constexpr Direction UpLeft   = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
 
     const Square ksq = pos.square<KING>(Them);
-    Bitboard emptySquares;
+    const Bitboard emptySquares = Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces();
+    const Bitboard enemies      = Type == EVASIONS ? pos.checkers()
+                                : Type == CAPTURES ? target : pos.pieces(Them);
 
     Bitboard pawnsOn7    = pos.pieces(Us, PAWN) &  TRank7BB;
     Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
 
-    Bitboard enemies = (Type == EVASIONS ? pos.checkers():
-                        Type == CAPTURES ? target : pos.pieces(Them));
-
     // Single and double pawn pushes, no promotions
     if (Type != CAPTURES)
     {
-        emptySquares = (Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces());
-
         Bitboard b1 = shift<Up>(pawnsNotOn7)   & emptySquares;
         Bitboard b2 = shift<Up>(b1 & TRank3BB) & emptySquares;
 
@@ -82,22 +79,12 @@ namespace {
 
         if (Type == QUIET_CHECKS)
         {
-            b1 &= pawn_attacks_bb(Them, ksq);
-            b2 &= pawn_attacks_bb(Them, ksq);
-
-            // Add pawn pushes which give discovered check. This is possible only
-            // if the pawn is not on the same file as the enemy king, because we
-            // don't generate captures. Note that a possible discovered check
-            // promotion has been already generated amongst the captures.
-            Bitboard dcCandidateQuiets = pos.blockers_for_king(Them) & pawnsNotOn7;
-            if (dcCandidateQuiets)
-            {
-                Bitboard dc1 = shift<Up>(dcCandidateQuiets) & emptySquares & ~file_bb(ksq);
-                Bitboard dc2 = shift<Up>(dc1 & TRank3BB) & emptySquares;
-
-                b1 |= dc1;
-                b2 |= dc2;
-            }
+            // To make a quiet check, you either make a direct check by pushing a pawn
+            // or push a blocker pawn that is not on the same file as the enemy king.
+            // Discovered check promotion has been already generated amongst the captures.
+            Bitboard dcCandidatePawns = pos.blockers_for_king(Them) & ~file_bb(ksq);
+            b1 &= pawn_attacks_bb(Them, ksq) | shift<   Up>(dcCandidatePawns);
+            b2 &= pawn_attacks_bb(Them, ksq) | shift<Up+Up>(dcCandidatePawns);
         }
 
         while (b1)
@@ -116,16 +103,13 @@ namespace {
     // Promotions and underpromotions
     if (pawnsOn7)
     {
-        if (Type == CAPTURES)
-            emptySquares = ~pos.pieces();
-
-        if (Type == EVASIONS)
-            emptySquares &= target;
-
         Bitboard b1 = shift<UpRight>(pawnsOn7) & enemies;
         Bitboard b2 = shift<UpLeft >(pawnsOn7) & enemies;
         Bitboard b3 = shift<Up     >(pawnsOn7) & emptySquares;
 
+        if (Type == EVASIONS)
+            b3 &= target;
+
         while (b1)
             moveList = make_promotions<Type, UpRight>(moveList, pop_lsb(b1), ksq);
 
@@ -185,8 +169,9 @@ namespace {
     while (bb)
     {
         Square from = pop_lsb(bb);
-
         Bitboard b = attacks_bb<Pt>(from, pos.pieces()) & target;
+
+        // To check, you either move freely a blocker or make a direct check.
         if (Checks && (Pt == QUEEN || !(pos.blockers_for_king(~Us) & from)))
             b &= pos.check_squares(Pt);
 
@@ -206,26 +191,14 @@ namespace {
     constexpr bool Checks = Type == QUIET_CHECKS; // Reduce template instantiations
     const Square ksq = pos.square<KING>(Us);
     Bitboard target;
-    
+
     if (Type == EVASIONS && more_than_one(pos.checkers()))
         goto kingMoves; // Double check, only a king move can save the day
 
-    switch (Type)
-    {
-        case CAPTURES:
-            target =  pos.pieces(~Us);
-            break;
-        case QUIETS:
-        case QUIET_CHECKS:
-            target = ~pos.pieces();
-            break;
-        case EVASIONS:
-            target = between_bb(ksq, lsb(pos.checkers()));
-            break;
-        case NON_EVASIONS:
-            target = ~pos.pieces(Us);
-            break;
-    }
+    target = Type == EVASIONS     ?  between_bb(ksq, lsb(pos.checkers()))
+           : Type == NON_EVASIONS ? ~pos.pieces( Us)
+           : Type == CAPTURES     ?  pos.pieces(~Us)
+                                  : ~pos.pieces(   ); // QUIETS || QUIET_CHECKS
 
     moveList = generate_pawn_moves<Us, Type>(pos, moveList, target);
     moveList = generate_moves<Us, KNIGHT, Checks>(pos, moveList, target);