X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=945169c36d5ae8544078873ae43a686a6a825437;hp=8be7cea4b6ae6b098dfa2537904d0885ed2daa8f;hb=2c1ba2ab0dad2421b8ed1bd3c049634f1f00dfc3;hpb=0446fc85dec483d1887adc22a3d729b0cacd8328

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 8be7cea4..945169c3 100644
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -45,6 +45,7 @@ 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];
@@ -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
       {