Simplify away the piece count condition for useClassical. In compensation, the psq requirement is increased by 15%.
Also updated the Elo estimate for useClassical, based on recent testing.
Simplification STC:
https://tests.stockfishchess.org/tests/view/
642acbb577ff3301150d3ef5
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 51984 W: 13906 L: 13707 D: 24371
Ptnml(0-2): 150, 5638, 14227, 5817, 160
Simplification LTC:
https://tests.stockfishchess.org/tests/view/
642b9c5777ff3301150d778a
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 119696 W: 32412 L: 32300 D: 54984
Ptnml(0-2): 53, 11529, 36567, 11651, 48
closes https://github.com/official-stockfish/Stockfish/pull/4494
Bench:
5089321
// 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 and several pieces remain. (~3 Elo)
- bool useClassical = !useNNUE || (pos.count<ALL_PIECES>() > 7 && abs(psq) > 1781);
+ // PSQ advantage is decisive. (~4 Elo at STC, 1 Elo at LTC)
+ bool useClassical = !useNNUE || abs(psq) > 2048;
if (useClassical)
v = Evaluation<NO_TRACE>(pos).value();