No classical eval. Bench: 3492488

src/evaluate.cpp

@@ -1113,43 +1113,12 @@ Value Eval::evaluate(const Position& pos) {
       v = Evaluation<NO_TRACE>(pos).value();
   else
   {
-      // Scale and shift NNUE for compatibility with search and classical evaluation
-      auto  adjusted_NNUE = [&]()
-      {
-
-         int scale = 903 + 28 * pos.count<PAWN>() + 28 * pos.non_pawn_material() / 1024;
-
-         Value nnue = NNUE::evaluate(pos, true) * scale / 1024;
-
-         if (pos.is_chess960())
-             nnue += fix_FRC(pos);
-
-         return nnue;
-      };
-
-      // If there is PSQ imbalance we use the classical eval. We also introduce
-      // a small probability of using the classical eval when PSQ imbalance is small.
-      Value psq = Value(abs(eg_value(pos.psq_score())));
-      int   r50 = 16 + pos.rule50_count();
-      bool  largePsq = psq * 16 > (NNUEThreshold1 + pos.non_pawn_material() / 64) * r50;
-
-      // Use classical evaluation for really low piece endgames.
-      // One critical case is the draw for bishop + A/H file pawn vs naked king.
-      bool lowPieceEndgame =   pos.non_pawn_material() == BishopValueMg
-                            || (pos.non_pawn_material() < 2 * RookValueMg && pos.count<PAWN>() < 2);
-
-      v = largePsq || lowPieceEndgame ? Evaluation<NO_TRACE>(pos).value()  // classical
-                                      : adjusted_NNUE();                   // NNUE
-
-      // If the classical eval is small and imbalance large, use NNUE nevertheless.
-      // For the case of opposite colored bishops, switch to NNUE eval with small
-      // probability if the classical eval is less than the threshold.
-      if (    largePsq
-          && !lowPieceEndgame
-          && (   abs(v) * 16 < NNUEThreshold2 * r50
-              || (   pos.opposite_bishops()
-                  && abs(v) * 16 < (NNUEThreshold1 + pos.non_pawn_material() / 64) * r50)))
-          v = adjusted_NNUE();
+      int scale = 903 + 28 * pos.count<PAWN>() + 28 * pos.non_pawn_material() / 1024;
+
+      v = NNUE::evaluate(pos, true) * scale / 1024;
+
+      if (pos.is_chess960())
+          v += fix_FRC(pos);
   }
 
   // Damp down the evaluation linearly when shuffling