Updated KNNKP endgame.

[stockfish] / src / endgame.cpp

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 6745ee2664c612689646c283f78833355d509dcf..74e16fa6941b0e5e6196c4b319cbd122d6fa5940 100644 (file)
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -310,16 +310,17 @@ Value Endgame<KQKR>::operator()(const Position& pos) const {
 }
 
 
-/// KNN vs KP. Simply push the opposing king to the corner
+/// KNN vs KP. Very drawish, but there are some mate opportunities if we can
+//  press the weakSide King to a corner before the pawn advances too much.
 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)];
+  Value result =      PawnValueEg
+               +  2 * PushToEdges[pos.square<KING>(weakSide)]
+               - 10 * relative_rank(weakSide, pos.square<PAWN>(weakSide));
 
   return strongSide == pos.side_to_move() ? result : -result;
 }