Reformat pick_random() in magics calculation

[stockfish] / src / bitboard.cpp

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 40cdbb21ff956601238b0db0dc72176e5cb081cb..8be7cea4b6ae6b098dfa2537904d0885ed2daa8f 100644 (file)
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -45,12 +45,11 @@ Bitboard ThisAndAdjacentFilesBB[8];
 Bitboard InFrontBB[2][8];
 Bitboard StepAttacksBB[16][64];
 Bitboard BetweenBB[64][64];
-Bitboard SquaresInFrontMask[2][64];
+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 +60,7 @@ 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);
 
@@ -142,7 +142,7 @@ 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 & make_square(file, rank) ? "X " : "  ");
 
       std::cout << "|\n";
   }
@@ -168,30 +168,27 @@ void Bitboards::init() {
   FileBB[FILE_A] = FileABB;
   RankBB[RANK_1] = Rank1BB;
 
-  for (int f = FILE_B; f <= FILE_H; f++)
+  for (int i = 1; i < 8; i++)
   {
-      FileBB[f] = FileBB[f - 1] << 1;
-      RankBB[f] = RankBB[f - 1] << 8;
+      FileBB[i] = FileBB[i - 1] << 1;
+      RankBB[i] = RankBB[i - 1] << 8;
   }
 
-  for (int f = FILE_A; f <= FILE_H; f++)
+  for (File f = FILE_A; f <= FILE_H; f++)
   {
       AdjacentFilesBB[f] = (f > FILE_A ? FileBB[f - 1] : 0) | (f < FILE_H ? FileBB[f + 1] : 0);
       ThisAndAdjacentFilesBB[f] = FileBB[f] | AdjacentFilesBB[f];
   }
 
-  for (int rw = RANK_7, rb = RANK_2; rw >= RANK_1; rw--, rb++)
-  {
-      InFrontBB[WHITE][rw] = InFrontBB[WHITE][rw + 1] | RankBB[rw + 1];
-      InFrontBB[BLACK][rb] = InFrontBB[BLACK][rb - 1] | RankBB[rb - 1];
-  }
+  for (Rank r = RANK_1; r < RANK_8; r++)
+      InFrontBB[WHITE][r] = ~(InFrontBB[BLACK][r + 1] = InFrontBB[BLACK][r] | RankBB[r]);
 
   for (Color c = WHITE; c <= BLACK; c++)
       for (Square s = SQ_A1; s <= SQ_H8; s++)
       {
-          SquaresInFrontMask[c][s] = in_front_bb(c, s) & file_bb(s);
-          PassedPawnMask[c][s]     = in_front_bb(c, s) & this_and_adjacent_files_bb(file_of(s));
-          AttackSpanMask[c][s]     = in_front_bb(c, s) & adjacent_files_bb(file_of(s));
+          ForwardBB[c][s]      = InFrontBB[c][rank_of(s)] & FileBB[file_of(s)];
+          PassedPawnMask[c][s] = InFrontBB[c][rank_of(s)] & ThisAndAdjacentFilesBB[file_of(s)];
+          AttackSpanMask[c][s] = InFrontBB[c][rank_of(s)] & AdjacentFilesBB[file_of(s)];
       }
 
   for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
@@ -231,9 +228,8 @@ void Bitboards::init() {
 
   for (Square s = SQ_A1; s <= SQ_H8; s++)
   {
-      PseudoAttacks[BISHOP][s] = attacks_bb<BISHOP>(s, 0);
-      PseudoAttacks[ROOK][s]   = attacks_bb<ROOK>(s, 0);
-      PseudoAttacks[QUEEN][s]  = PseudoAttacks[BISHOP][s] | PseudoAttacks[ROOK][s];
+      PseudoAttacks[QUEEN][s]  = PseudoAttacks[BISHOP][s] = attacks_bb<BISHOP>(s, 0);
+      PseudoAttacks[QUEEN][s] |= PseudoAttacks[  ROOK][s] = attacks_bb<  ROOK>(s, 0);
   }
 
   for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
@@ -269,25 +265,17 @@ 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>();
   }
 
 
@@ -340,7 +328,9 @@ 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
@@ -354,6 +344,8 @@ namespace {
                 if (attack && attack != reference[i])
                     break;
 
+                assert(reference[i] != 0);
+
                 attack = reference[i];
             }
         } while (i != size);