- // Deciding between classical and NNUE eval: for high PSQ imbalance we use classical,
- // but we switch to NNUE during long shuffling or with high material on the board.
- bool useClassical = !useNNUE ||
- ((pos.count<ALL_PIECES>() > 7)
- && abs(psq) * 5 > (856 + pos.non_pawn_material() / 64) * (10 + pos.rule50_count()));
+ // We use the much less accurate but faster Classical eval when the NNUE
+ // option is set to false. Otherwise we use the NNUE eval unless the
+ // PSQ advantage is decisive. (~4 Elo at STC, 1 Elo at LTC)
+ bool useClassical = !useNNUE || abs(psq) > 2048;