Fix initialization of BSFTable[]

[stockfish] / src / bitboard.cpp

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 0e31d5d69adccca37458c0ca8b9ddf9b9d44d49f..44e00da0a4cb25f4257a643e716da49c51783064 100644 (file)
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -79,7 +79,7 @@ void print_bitboard(Bitboard b) {
   {
       std::cout << "+---+---+---+---+---+---+---+---+" << '\n';
       for (File f = FILE_A; f <= FILE_H; f++)
-          std::cout << "| " << (bit_is_set(b, make_square(f, r)) ? 'X' : ' ') << ' ';
+          std::cout << "| " << (bit_is_set(b, make_square(f, r)) ? "X " : "  ");
 
       std::cout << "|\n";
   }
@@ -159,7 +159,7 @@ void init_bitboards() {
 
   for (Square s = SQ_A1; s <= SQ_H8; s++)
   {
-      SetMaskBB[s] = (1ULL << s);
+      SetMaskBB[s] = 1ULL << s;
       ClearMaskBB[s] = ~SetMaskBB[s];
   }
 
@@ -195,9 +195,9 @@ void init_bitboards() {
       }
 
   for (Bitboard b = 0; b < 256; b++)
-      BitCount8Bit[b] = (uint8_t)count_1s<CNT32>(b);
+      BitCount8Bit[b] = (uint8_t)count_1s<CNT32_MAX15>(b);
 
-  for (int i = 1; i < 64; i++)
+  for (int i = 0; i < 64; i++)
       if (!CpuIs64Bit) // Matt Taylor's folding trick for 32 bit systems
       {
           Bitboard b = 1ULL << i;
@@ -208,9 +208,8 @@ void init_bitboards() {
       else
           BSFTable[((1ULL << i) * 0x218A392CD3D5DBFULL) >> 58] = i;
 
-  int steps[][9] = {
-    {0}, {7,9,0}, {17,15,10,6,-6,-10,-15,-17,0}, {0}, {0}, {0}, {9,7,-7,-9,8,1,-1,-8,0}
-  };
+  int steps[][9] = { {}, { 7, 9 }, { 17, 15, 10, 6, -6, -10, -15, -17 },
+                     {}, {}, {}, { 9, 7, -7, -9, 8, 1, -1, -8 } };
 
   for (Color c = WHITE; c <= BLACK; c++)
       for (Square s = SQ_A1; s <= SQ_H8; s++)
@@ -223,11 +222,11 @@ void init_bitboards() {
                       set_bit(&StepAttacksBB[make_piece(c, pt)][s], to);
               }
 
-  Square RDeltas[] = { DELTA_N,  DELTA_E,  DELTA_S,  DELTA_W  };
-  Square BDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW };
+  Square RDelta[] = { DELTA_N,  DELTA_E,  DELTA_S,  DELTA_W  };
+  Square BDelta[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW };
 
-  init_sliding_attacks(BMult, BAttacks, BAttacksTable, BMask, BShift, BDeltas);
-  init_sliding_attacks(RMult, RAttacks, RAttacksTable, RMask, RShift, RDeltas);
+  init_sliding_attacks(BMult, BAttacks, BAttacksTable, BMask, BShift, BDelta);
+  init_sliding_attacks(RMult, RAttacks, RAttacksTable, RMask, RShift, RDelta);
 
   for (Square s = SQ_A1; s <= SQ_H8; s++)
   {
@@ -255,27 +254,33 @@ namespace {
 
   Bitboard submask(Bitboard mask, int key) {
 
-    Bitboard subMask = 0;
-    int bitNum = -1;
+    Bitboard b, subMask = 0;
+    int bitProbe = 1;
 
     // Extract an unique submask out of a mask according to the given key
-    for (Square s = SQ_A1; s <= SQ_H8; s++)
-        if (bit_is_set(mask, s) && bit_is_set(key, Square(++bitNum)))
-            set_bit(&subMask, s);
+    while (mask)
+    {
+        b = mask & -mask;
+        mask ^= b;
 
+        if (key & bitProbe)
+            subMask |= b;
+
+        bitProbe <<= 1;
+    }
     return subMask;
   }
 
-  Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[], Bitboard excluded) {
+  Bitboard sliding_attacks(Square sq, Bitboard occupied, Square delta[], Bitboard excluded) {
 
     Bitboard attacks = 0;
 
     for (int i = 0; i < 4; i++)
     {
-        Square s = sq + deltas[i];
+        Square s = sq + delta[i];
 
         while (    square_is_ok(s)
-               &&  square_distance(s, s - deltas[i]) == 1
+               &&  square_distance(s, s - delta[i]) == 1
                && !bit_is_set(excluded, s))
         {
             set_bit(&attacks, s);
@@ -283,26 +288,27 @@ namespace {
             if (bit_is_set(occupied, s))
                 break;
 
-            s += deltas[i];
+            s += delta[i];
         }
     }
     return attacks;
   }
 
-  template<bool Is64>
   Bitboard pick_magic(Bitboard mask, RKISS& rk, int booster) {
 
     Bitboard magic;
 
-    // Advance PRNG state of a quantity known to be the optimal to
-    // quickly retrieve all the magics.
-    for (int i = 0; i < booster; i++)
-        rk.rand<Bitboard>();
+    // Values s1 and s2 are used to rotate the candidate magic of a
+    // quantity known to be the optimal to quickly find the magics.
+    int s1 = booster & 63, s2 = (booster >> 6) & 63;
 
     while (true)
     {
-        magic = rk.rand<Bitboard>() & rk.rand<Bitboard>();
-        magic &= Is64 ? rk.rand<Bitboard>() : (rk.rand<Bitboard>() | rk.rand<Bitboard>());
+        magic = rk.rand<Bitboard>();
+        magic = (magic >> s1) | (magic << (64 - s1));
+        magic &= rk.rand<Bitboard>();
+        magic = (magic >> s2) | (magic << (64 - s2));
+        magic &= rk.rand<Bitboard>();
 
         if (BitCount8Bit[(mask * magic) >> 56] >= 6)
             return magic;
@@ -312,8 +318,8 @@ namespace {
   void init_sliding_attacks(Bitboard magic[], Bitboard* attack[], Bitboard attTable[],
                             Bitboard mask[], int shift[], Square delta[]) {
 
-    const int  MagicBoosters[][8] = { { 55, 11, 17,  2, 39,  3, 31, 44 },
-                                      { 26, 21, 21, 32, 31,  9,  5, 11 } };
+    const int  MagicBoosters[][8] = { { 3191, 2184, 1310, 3618, 2091, 1308, 2452, 3996 },
+                                      { 1059, 3608,  605, 3234, 3326,   38, 2029, 3043 } };
     RKISS rk;
     Bitboard occupancy[4096], reference[4096], excluded;
     int key, maxKey, index, booster, offset = 0;
@@ -324,9 +330,9 @@ namespace {
 
         attack[s] = &attTable[offset];
         mask[s]   = sliding_attacks(s, EmptyBoardBB, delta, excluded);
-        shift[s]  = (CpuIs64Bit ? 64 : 32) - count_1s<CNT64>(mask[s]);
+        shift[s]  = (CpuIs64Bit ? 64 : 32) - count_1s<CNT32_MAX15>(mask[s]);
 
-        maxKey = 1 << count_1s<CNT32>(mask[s]);
+        maxKey = 1 << count_1s<CNT32_MAX15>(mask[s]);
         offset += maxKey;
         booster = MagicBoosters[CpuIs64Bit][square_rank(s)];
 
@@ -339,7 +345,7 @@ namespace {
 
         // Then find a possible magic and the corresponding attacks
         do {
-            magic[s] = pick_magic<CpuIs64Bit>(mask[s], rk, booster);
+            magic[s] = pick_magic(mask[s], rk, booster);
             memset(attack[s], 0, maxKey * sizeof(Bitboard));
 
             for (key = 0; key < maxKey; key++)