X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=945169c36d5ae8544078873ae43a686a6a825437;hp=1bae6843df5303d3d7379e335debd7c02946b898;hb=2c1ba2ab0dad2421b8ed1bd3c049634f1f00dfc3;hpb=2f47844c7cb34c7de5b5d41cda10b7d8736a20bc

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 1bae6843..945169c3 100644
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -45,12 +45,12 @@ Bitboard ThisAndAdjacentFilesBB[8];
 Bitboard InFrontBB[2][8];
 Bitboard StepAttacksBB[16][64];
 Bitboard BetweenBB[64][64];
+Bitboard DistanceRingsBB[64][8];
 Bitboard ForwardBB[2][64];
 Bitboard PassedPawnMask[2][64];
 Bitboard AttackSpanMask[2][64];
 Bitboard PseudoAttacks[6][64];
 
-uint8_t BitCount8Bit[256];
 int SquareDistance[64][64];
 
 namespace {
@@ -61,6 +61,7 @@ namespace {
   int MS1BTable[256];
   Bitboard RTable[0x19000]; // Storage space for rook attacks
   Bitboard BTable[0x1480];  // Storage space for bishop attacks
+  uint8_t BitCount8Bit[256];
 
   typedef unsigned (Fn)(Square, Bitboard);
 
@@ -68,40 +69,35 @@ namespace {
                    Bitboard masks[], unsigned shifts[], Square deltas[], Fn index);
 }
 
-/// first_1() finds the least significant nonzero bit in a nonzero bitboard.
-/// pop_1st_bit() finds and clears the least significant nonzero bit in a
-/// nonzero bitboard.
+/// lsb()/msb() finds the least/most significant bit in a nonzero bitboard.
+/// pop_lsb() finds and clears the least significant bit in a nonzero bitboard.
 
-#if defined(IS_64BIT) && !defined(USE_BSFQ)
+#if !defined(USE_BSFQ)
 
-Square first_1(Bitboard b) {
-  return Square(BSFTable[((b & -b) * 0x218A392CD3D5DBFULL) >> 58]);
-}
-
-Square pop_1st_bit(Bitboard* b) {
-  Bitboard bb = *b;
-  *b &= (*b - 1);
-  return Square(BSFTable[((bb & -bb) * 0x218A392CD3D5DBFULL) >> 58]);
-}
+Square lsb(Bitboard b) {
 
-#elif !defined(USE_BSFQ)
+  if (Is64Bit)
+      return Square(BSFTable[((b & -b) * 0x218A392CD3D5DBFULL) >> 58]);
 
-Square first_1(Bitboard b) {
   b ^= (b - 1);
   uint32_t fold = unsigned(b) ^ unsigned(b >> 32);
   return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
 }
 
-Square pop_1st_bit(Bitboard* b) {
+Square pop_lsb(Bitboard* b) {
 
   Bitboard bb = *b;
   *b = bb & (bb - 1);
+
+  if (Is64Bit)
+      return Square(BSFTable[((bb & -bb) * 0x218A392CD3D5DBFULL) >> 58]);
+
   bb ^= (bb - 1);
   uint32_t fold = unsigned(bb) ^ unsigned(bb >> 32);
   return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
 }
 
-Square last_1(Bitboard b) {
+Square msb(Bitboard b) {
 
   unsigned b32;
   int result = 0;
@@ -142,7 +138,7 @@ void Bitboards::print(Bitboard b) {
       std::cout << "+---+---+---+---+---+---+---+---+" << '\n';
 
       for (File file = FILE_A; file <= FILE_H; file++)
-          std::cout << "| " << ((b & make_square(file, rank)) ? "X " : "  ");
+          std::cout << "| " << (b & (file | rank) ? "X " : "  ");
 
       std::cout << "|\n";
   }
@@ -195,6 +191,12 @@ void Bitboards::init() {
       for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
           SquareDistance[s1][s2] = std::max(file_distance(s1, s2), rank_distance(s1, s2));
 
+  for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
+      for (int d = 1; d < 8; d++)
+          for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
+              if (SquareDistance[s1][s2] == d)
+                  DistanceRingsBB[s1][d - 1] |= s2;
+
   for (int i = 0; i < 64; i++)
       if (!Is64Bit) // Matt Taylor's folding trick for 32 bit systems
       {
@@ -265,25 +267,17 @@ namespace {
   }
 
 
-  Bitboard pick_random(Bitboard mask, RKISS& rk, int booster) {
-
-    Bitboard magic;
+  Bitboard pick_random(RKISS& rk, int booster) {
 
     // 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>();
-        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;
-    }
+    Bitboard m = rk.rand<Bitboard>();
+    m = (m >> s1) | (m << (64 - s1));
+    m &= rk.rand<Bitboard>();
+    m = (m >> s2) | (m << (64 - s2));
+    return m & rk.rand<Bitboard>();
   }
 
 
@@ -336,7 +330,9 @@ namespace {
         // Find a magic for square 's' picking up an (almost) random number
         // until we find the one that passes the verification test.
         do {
-            magics[s] = pick_random(masks[s], rk, booster);
+            do magics[s] = pick_random(rk, booster);
+            while (BitCount8Bit[(magics[s] * masks[s]) >> 56] < 6);
+
             memset(attacks[s], 0, size * sizeof(Bitboard));
 
             // A good magic must map every possible occupancy to an index that
@@ -350,6 +346,8 @@ namespace {
                 if (attack && attack != reference[i])
                     break;
 
+                assert(reference[i] != 0);
+
                 attack = reference[i];
             }
         } while (i != size);