Queen vs. Minors imbalance

[stockfish] / src / material.cpp

diff --git a/src/material.cpp b/src/material.cpp
index dc2a3a3b550c6eddaf9e8e1d378e5921c77bf72b..114f083171fe748423c83070cb619d853ad44096 100644 (file)
--- a/src/material.cpp
+++ b/src/material.cpp
@@ -58,6 +58,12 @@ namespace {
     24, -32, 107, -51, 117, -9, -126, -21, 31
   };
 
+  // QueenMinorsImbalance[opp_minor_count] is applied when only one side has a queen.
+  // It contains a bonus/malus for the side with the queen.
+  const int QueenMinorsImbalance[16] = { 
+    31, -8, -15, -25, -5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+  };
+
   // Endgame evaluation and scaling functions are accessed directly and not through
   // the function maps because they correspond to more than one material hash key.
   Endgame<KXK>    EvaluateKXK[] = { Endgame<KXK>(WHITE),    Endgame<KXK>(BLACK) };
@@ -111,6 +117,10 @@ namespace {
         bonus += pieceCount[Us][pt1] * v;
     }
 
+    // Special handling of Queen vs. Minors
+    if  (pieceCount[Us][QUEEN] == 1 && pieceCount[Them][QUEEN] == 0)
+         bonus += QueenMinorsImbalance[pieceCount[Them][KNIGHT] + pieceCount[Them][BISHOP]];
+
     return bonus;
   }