NNUE evaluation threshold

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index f43c62d687118d812761fc7e992b0ee2639243a3..09496fdcab7331af336846875664d814eaa1fc54 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -107,9 +107,10 @@ using namespace Trace;
 namespace {
 
   // Threshold for lazy and space evaluation
-  constexpr Value LazyThreshold1  = Value(1400);
-  constexpr Value LazyThreshold2  = Value(1300);
+  constexpr Value LazyThreshold1 =  Value(1400);
+  constexpr Value LazyThreshold2 =  Value(1300);
   constexpr Value SpaceThreshold = Value(12222);
+  constexpr Value NNUEThreshold  =   Value(500);
 
   // KingAttackWeights[PieceType] contains king attack weights by piece type
   constexpr int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 81, 52, 44, 10 };
@@ -941,9 +942,14 @@ make_v:
 Value Eval::evaluate(const Position& pos) {
 
   if (Eval::useNNUE)
-      return NNUE::evaluate(pos);
-  else
-      return Evaluation<NO_TRACE>(pos).value();
+  {
+      Value balance = pos.non_pawn_material(WHITE) - pos.non_pawn_material(BLACK);
+      balance += 200 * (pos.count<PAWN>(WHITE) - pos.count<PAWN>(BLACK));
+      // Take NNUE eval only on balanced positions
+      if (abs(balance) < NNUEThreshold)
+         return NNUE::evaluate(pos);
+  }
+  return Evaluation<NO_TRACE>(pos).value();
 }
 
 /// trace() is like evaluate(), but instead of returning a value, it returns