Changes

In August 2020 a new patch changed Stockfish NNUE into a hybrid engine: it uses NNUE evaluation only on quite balanced material positions, otherwise uses the classical one. It could speed up to 10% and gain 20 Elo <ref>[https://github.com/official-stockfish/Stockfish/pull/2916 NNUE evaluation threshold by MJZ1977 · Pull Request #2916 · official-stockfish/Stockfish · GitHub], August 06, 2020</ref>. At that point, NNUE helped increasing around 100 Elo for Stockfish.