X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.h;h=2280f66c808e4b67722bf81e834e17c723589d3d;hp=b193786cb8e28eae2096cbcb9095b14dd006cf5c;hb=3e6e57231ecb1c23e43e02109efa3bcaf7ebe7c3;hpb=aaad48464bc8a269634de371238826d09a6e240d

diff --git a/src/bitboard.h b/src/bitboard.h
index b193786c..2280f66c 100644
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -236,6 +236,19 @@ inline Bitboard in_front_bb(Color c, Square s) {
 }
 
 
+/// behind_bb() takes a color and a rank or square as input, and returns a
+/// bitboard representing all the squares on all ranks behind of the rank
+/// (or square), from the given color's point of view.
+
+inline Bitboard behind_bb(Color c, Rank r) {
+  return InFrontBB[opposite_color(c)][r];
+}
+
+inline Bitboard behind_bb(Color c, Square s) {
+  return in_front_bb(opposite_color(c), square_rank(s));
+}
+
+
 /// ray_bb() gives a bitboard representing all squares along the ray in a
 /// given direction from a given square.
 
@@ -382,24 +395,23 @@ inline int count_1s_max_15(Bitboard b) {
 
 inline int count_1s(Bitboard b) {
   unsigned w = unsigned(b >> 32), v = unsigned(b);
-  v = v - ((v >> 1) & 0x55555555);
-  w = w - ((w >> 1) & 0x55555555);
-  v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
-  w = (w & 0x33333333) + ((w >> 2) & 0x33333333);
-  v = (v + (v >> 4)) & 0x0F0F0F0F;
-  w = (w + (w >> 4)) & 0x0F0F0F0F;
-  v = ((v+w) * 0x01010101) >> 24; // mul is fast on amd procs
-  return int(v);
+  v -= (v >> 1) & 0x55555555;
+  w -= (w >> 1) & 0x55555555;
+  v += w;
+  v = ((v >> 2) & 0x33333333) + (v & 0x33333333);
+  v = ((v >> 4) + v) & 0x0F0F0F0F;
+  v *= 0x01010101; // mul is fast on amd procs
+  return int(v >> 24);
 }
 
 inline int count_1s_max_15(Bitboard b) {
   unsigned w = unsigned(b >> 32), v = unsigned(b);
-  v = v - ((v >> 1) & 0x55555555);
-  w = w - ((w >> 1) & 0x55555555);
-  v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
-  w = (w & 0x33333333) + ((w >> 2) & 0x33333333);
-  v = ((v+w) * 0x11111111) >> 28;
-  return int(v);
+  v -= (v >> 1) & 0x55555555;
+  w -= (w >> 1) & 0x55555555;
+  v += w;
+  v = ((v >> 2) & 0x33333333) + (v & 0x33333333);
+  v *= 0x11111111;
+  return int(v >> 28);
 }
 
 #elif defined(BITCOUNT_SWAR_64)