Simplify distance (#2109)

[stockfish] / src / endgame.cpp

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 835173c468b68bed46b7159dfafe5e32d74c9b0a..5958e633d90e271e9fef852014defd7d6000164b 100644 (file)
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -18,7 +18,6 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <algorithm>
 #include <cassert>
 
 #include "bitboard.h"
@@ -77,10 +76,7 @@ namespace {
     if (file_of(pos.square<PAWN>(strongSide)) >= FILE_E)
         sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1
 
-    if (strongSide == BLACK)
-        sq = ~sq;
-
-    return sq;
+    return strongSide == WHITE ? sq : ~sq;
   }
 
 } // namespace
@@ -286,6 +282,21 @@ Value Endgame<KQKR>::operator()(const Position& pos) const {
 }
 
 
+/// KNN vs KP. Simply push the opposing king to the corner
+template<>
+Value Endgame<KNNKP>::operator()(const Position& pos) const {
+
+  assert(verify_material(pos, strongSide, 2 * KnightValueMg, 0));
+  assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
+
+  Value result =  2 * KnightValueEg
+                - PawnValueEg
+                + PushToEdges[pos.square<KING>(weakSide)];
+
+  return strongSide == pos.side_to_move() ? result : -result;
+}
+
+
 /// Some cases of trivial draws
 template<> Value Endgame<KNNK>::operator()(const Position&) const { return VALUE_DRAW; }
 
@@ -624,8 +635,6 @@ ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
   Square ksq = pos.square<KING>(weakSide);
   Square psq1 = pos.squares<PAWN>(strongSide)[0];
   Square psq2 = pos.squares<PAWN>(strongSide)[1];
-  Rank r1 = rank_of(psq1);
-  Rank r2 = rank_of(psq2);
   Square blockSq1, blockSq2;
 
   if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2))
@@ -659,7 +668,7 @@ ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
         && opposite_colors(ksq, wbsq)
         && (   bbsq == blockSq2
             || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakSide, BISHOP))
-            || distance(r1, r2) >= 2))
+            || distance<Rank>(psq1, psq2) >= 2))
         return SCALE_FACTOR_DRAW;
 
     else if (   ksq == blockSq2