Blend nnue complexity with classical.

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 718c7bc035da95f92718e73fe599ee376ff793d7..415c18c557395cad0bd7b1bc2c5956a5daa21679 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -192,7 +192,6 @@ using namespace Trace;
 
 namespace {
 
-
   // Threshold for lazy and space evaluation
   constexpr Value LazyThreshold1    =  Value(3631);
   constexpr Value LazyThreshold2    =  Value(2084);
@@ -1084,13 +1083,14 @@ make_v:
 Value Eval::evaluate(const Position& pos) {
 
   Value v;
-  bool useClassical = false;
+  // 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.this_thread()->depth > 9 || pos.count<ALL_PIECES>() > 7) &&
+          abs(eg_value(pos.psq_score())) * 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,
   // but we switch to NNUE during long shuffling or with high material on the board.
-  if (  !useNNUE
-      || ((pos.this_thread()->depth > 9 || pos.count<ALL_PIECES>() > 7) &&
-          abs(eg_value(pos.psq_score())) * 5 > (856 + pos.non_pawn_material() / 64) * (10 + pos.rule50_count())))
+  if (!useNNUE || useClassical)
   {
       v = Evaluation<NO_TRACE>(pos).value();          // classical
       useClassical = abs(v) >= 297;
@@ -1099,15 +1099,16 @@ Value Eval::evaluate(const Position& pos) {
   // If result of a classical evaluation is much lower than threshold fall back to NNUE
   if (useNNUE && !useClassical)
   {
-       Value nnue     = NNUE::evaluate(pos, true);     // NNUE
-       int scale      = 1014 + 21 * pos.non_pawn_material() / 1024;
+       int complexity;
+       int scale      = 1048 + 109 * pos.non_pawn_material() / 5120;
        Color stm      = pos.side_to_move();
        Value optimism = pos.this_thread()->optimism[stm];
        Value psq      = (stm == WHITE ? 1 : -1) * eg_value(pos.psq_score());
-       int complexity = 35 * abs(nnue - psq) / 256;
+       Value nnue     = NNUE::evaluate(pos, true, &complexity);     // NNUE
 
-       optimism = optimism * (32 + complexity) / 32;
-       v = (nnue * scale + optimism * (scale - 846)) / 1024;
+       complexity = (137 * complexity + 137 * abs(nnue - psq)) / 256;
+       optimism = optimism * (255 + complexity) / 256;
+       v = (nnue * scale + optimism * (scale - 848)) / 1024;
 
        if (pos.is_chess960())
            v += fix_FRC(pos);