The idea is that if classical eval returns a value much lower than the threshold of
its usage it most likely means that position isn't that simple
so we need the more precise NNUE evaluation.
passed STC:
https://tests.stockfishchess.org/tests/view/
61bf3e7557a0d0f327c3c47a
LLR: 2.95 (-2.94,2.94) <0.00,2.50>
Total: 108072 W: 28007 L: 27604 D: 52461
Ptnml(0-2): 352, 12147, 28650, 12520, 367
passed LTC:
https://tests.stockfishchess.org/tests/view/
61c0581657a0d0f327c3fa0c
LLR: 2.95 (-2.94,2.94) <0.50,3.00>
Total: 155096 W: 40392 L: 39841 D: 74863
Ptnml(0-2): 88, 15983, 44843, 16558, 76
closes https://github.com/official-stockfish/Stockfish/pull/3869
bench
4310422
// Deciding between classical and NNUE eval (~10 Elo): for high PSQ imbalance we use classical,
// but we switch to NNUE during long shuffling or with high material on the board.
// Deciding between classical and NNUE eval (~10 Elo): for high PSQ imbalance we use classical,
// but we switch to NNUE during long shuffling or with high material on the board.
+ bool classical = false;
+
if ( !useNNUE
|| abs(eg_value(pos.psq_score())) * 5 > (850 + pos.non_pawn_material() / 64) * (5 + pos.rule50_count()))
if ( !useNNUE
|| abs(eg_value(pos.psq_score())) * 5 > (850 + pos.non_pawn_material() / 64) * (5 + pos.rule50_count()))
v = Evaluation<NO_TRACE>(pos).value(); // classical
v = Evaluation<NO_TRACE>(pos).value(); // classical
+ classical = abs(v) >= 300;
+ }
+
+ // If result of a classical evaluation is much lower than threshold fall back to NNUE
+ if (!classical && useNNUE)
{
int scale = 1136
+ 20 * pos.non_pawn_material() / 1024;
{
int scale = 1136
+ 20 * pos.non_pawn_material() / 1024;