Simplify castlingPath (#2088)

Instead of looping through kfrom,kto, rfrom, rto, we can use BetweenBB. This is less lines of code and it is more clear what castlingPath actually is. Personal benchmarks are all over the place. However, this code is only executed when loading a position, so performance doesn't seem that relevant.

No functional change.

diff --git a/src/position.cpp b/src/position.cpp
index 84892d0..ada03fb 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -340,13 +340,8 @@ void Position::set_castling_right(Color c, Square rfrom) {
   Square kto = relative_square(c, cs == KING_SIDE ? SQ_G1 : SQ_C1);
   Square rto = relative_square(c, cs == KING_SIDE ? SQ_F1 : SQ_D1);
 
-  for (Square s = std::min(rfrom, rto); s <= std::max(rfrom, rto); ++s)
-      if (s != kfrom && s != rfrom)
-          castlingPath[cr] |= s;
-
-  for (Square s = std::min(kfrom, kto); s <= std::max(kfrom, kto); ++s)
-      if (s != kfrom && s != rfrom)
-          castlingPath[cr] |= s;
+  castlingPath[cr] = (between_bb(rfrom, rto) | between_bb(kfrom, kto) | rto | kto)
+                   & ~(square_bb(kfrom) | rfrom);
 }