X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=639ef3f06e968d7249c55ff45748577a9e6cfefa;hp=8be7cea4b6ae6b098dfa2537904d0885ed2daa8f;hb=6008f6538e9c3912c88e89d77ef3e3d3351a6e55;hpb=0446fc85dec483d1887adc22a3d729b0cacd8328

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 8be7cea4..639ef3f0 100644
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -23,6 +23,7 @@
 
 #include "bitboard.h"
 #include "bitcount.h"
+#include "misc.h"
 #include "rkiss.h"
 
 CACHE_LINE_ALIGNMENT
@@ -45,6 +46,7 @@ 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];
@@ -54,6 +56,10 @@ int SquareDistance[64][64];
 
 namespace {
 
+  // De Bruijn sequences. See chessprogramming.wikispaces.com/BitScan
+  const uint64_t DeBruijn_64 = 0x218A392CD3D5DBFULL;
+  const uint32_t DeBruijn_32 = 0x783A9B23;
+
   CACHE_LINE_ALIGNMENT
 
   int BSFTable[64];
@@ -68,40 +74,35 @@ 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.
-
-#if defined(IS_64BIT) && !defined(USE_BSFQ)
+/// 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.
 
-Square first_1(Bitboard b) {
-  return Square(BSFTable[((b & -b) * 0x218A392CD3D5DBFULL) >> 58]);
-}
+#if !defined(USE_BSFQ)
 
-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) * DeBruijn_64) >> 58]);
 
-Square first_1(Bitboard b) {
   b ^= (b - 1);
   uint32_t fold = unsigned(b) ^ unsigned(b >> 32);
-  return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
+  return Square(BSFTable[(fold * DeBruijn_32) >> 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) * DeBruijn_64) >> 58]);
+
   bb ^= (bb - 1);
   uint32_t fold = unsigned(bb) ^ unsigned(bb >> 32);
-  return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
+  return Square(BSFTable[(fold * DeBruijn_32) >> 26]);
 }
 
-Square last_1(Bitboard b) {
+Square msb(Bitboard b) {
 
   unsigned b32;
   int result = 0;
@@ -137,16 +138,18 @@ Square last_1(Bitboard b) {
 
 void Bitboards::print(Bitboard b) {
 
+  sync_cout;
+
   for (Rank rank = RANK_8; rank >= RANK_1; rank--)
   {
       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";
   }
-  std::cout << "+---+---+---+---+---+---+---+---+" << std::endl;
+  std::cout << "+---+---+---+---+---+---+---+---+" << sync_endl;
 }
 
 
@@ -195,16 +198,22 @@ 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
       {
           Bitboard b = 1ULL << i;
           b ^= b - 1;
           b ^= b >> 32;
-          BSFTable[(uint32_t)(b * 0x783A9B23) >> 26] = i;
+          BSFTable[(uint32_t)(b * DeBruijn_32) >> 26] = i;
       }
       else
-          BSFTable[((1ULL << i) * 0x218A392CD3D5DBFULL) >> 58] = i;
+          BSFTable[((1ULL << i) * DeBruijn_64) >> 58] = i;
 
   int steps[][9] = { {}, { 7, 9 }, { 17, 15, 10, 6, -6, -10, -15, -17 },
                      {}, {}, {}, { 9, 7, -7, -9, 8, 1, -1, -8 } };