Add PEXT software implementation

[stockfish] / src / bitboard.cpp

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index d4b8bcfdf2cabb53d59e20ff8a055688db6a54a8..27ba65747d6faf05cf4cdb3e2442aa0f0b7cdbe6 100644 (file)
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -79,6 +79,23 @@ namespace {
   }
 }
 
+
+/// Intel PEXT (parallel extraction) software implementation
+Bitboard pext(Bitboard b, Bitboard mask) {
+
+  Bitboard res = 0;
+
+  for (Bitboard bb = 1; mask; bb += bb)
+  {
+      if (b & mask & -mask)
+          res |= bb;
+
+      mask &= mask - 1;
+  }
+  return res;
+}
+
+
 /// lsb()/msb() finds the least/most significant bit in a non-zero bitboard.
 /// pop_lsb() finds and clears the least significant bit in a non-zero bitboard.
 
@@ -131,10 +148,10 @@ const std::string Bitboards::pretty(Bitboard b) {
 
   std::string s = "+---+---+---+---+---+---+---+---+\n";
 
-  for (Rank rank = RANK_8; rank >= RANK_1; --rank)
+  for (Rank r = RANK_8; r >= RANK_1; --r)
   {
-      for (File file = FILE_A; file <= FILE_H; ++file)
-          s.append(b & make_square(file, rank) ? "| X " : "|   ");
+      for (File f = FILE_A; f <= FILE_H; ++f)
+          s.append(b & make_square(f, r) ? "| X " : "|   ");
 
       s.append("|\n+---+---+---+---+---+---+---+---+\n");
   }