Value v;
Color stm = pos.side_to_move();
Value psq = pos.psq_eg_stm();
- // 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 useClassical = (pos.count<ALL_PIECES>() > 7)
- && abs(psq) * 5 > (856 + pos.non_pawn_material() / 64) * (10 + pos.rule50_count());
- // Deciding between classical and NNUE eval (~10 Elo): for high PSQ imbalance we use classical,
+ // 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.
- if (!useNNUE || useClassical)
- {
- v = Evaluation<NO_TRACE>(pos).value();
- useClassical = abs(v) >= 297;
- }
+ bool useClassical = !useNNUE ||
+ ((pos.count<ALL_PIECES>() > 7)
+ && abs(psq) * 5 > (856 + pos.non_pawn_material() / 64) * (10 + pos.rule50_count()));
- // If result of a classical evaluation is much lower than threshold fall back to NNUE
- if (useNNUE && !useClassical)
+ if (useClassical)
+ v = Evaluation<NO_TRACE>(pos).value();
+ else
{
- int nnueComplexity;
- int scale = 1064 + 106 * pos.non_pawn_material() / 5120;
- Value optimism = pos.this_thread()->optimism[stm];
-
- Value nnue = NNUE::evaluate(pos, true, &nnueComplexity);
- // Blend nnue complexity with (semi)classical complexity
- nnueComplexity = (104 * nnueComplexity + 131 * abs(nnue - psq)) / 256;
- if (complexity) // Return hybrid NNUE complexity to caller
- *complexity = nnueComplexity;
-
- optimism = optimism * (269 + nnueComplexity) / 256;
- v = (nnue * scale + optimism * (scale - 754)) / 1024;
+ int nnueComplexity;
+ int scale = 1064 + 106 * pos.non_pawn_material() / 5120;
+ Value optimism = pos.this_thread()->optimism[stm];
+
+ Value nnue = NNUE::evaluate(pos, true, &nnueComplexity);
+ // Blend nnue complexity with (semi)classical complexity
+ nnueComplexity = (104 * nnueComplexity + 131 * abs(nnue - psq)) / 256;
+ if (complexity) // Return hybrid NNUE complexity to caller
+ *complexity = nnueComplexity;
+
+ optimism = optimism * (269 + nnueComplexity) / 256;
+ v = (nnue * scale + optimism * (scale - 754)) / 1024;
}
// Damp down the evaluation linearly when shuffling
// When not using NNUE, return classical complexity to caller
if (complexity && (!useNNUE || useClassical))
- *complexity = abs(v - psq);
+ *complexity = abs(v - psq);
return v;
}