Use NNUE complexity in search, retune related parameters

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 415c18c557395cad0bd7b1bc2c5956a5daa21679..6d2e8da8d40d17057d8d42bad2ec9e8b9e39f33f 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -1080,35 +1080,39 @@ make_v:
 /// evaluate() is the evaluator for the outer world. It returns a static
 /// evaluation of the position from the point of view of the side to move.
 
-Value Eval::evaluate(const Position& pos) {
+Value Eval::evaluate(const Position& pos, int* complexity) {
 
   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.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());
+  bool useClassical =    (pos.this_thread()->depth > 9 || 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,
   // but we switch to NNUE during long shuffling or with high material on the board.
   if (!useNNUE || useClassical)
   {
-      v = Evaluation<NO_TRACE>(pos).value();          // classical
+      v = Evaluation<NO_TRACE>(pos).value();
       useClassical = abs(v) >= 297;
   }
 
   // If result of a classical evaluation is much lower than threshold fall back to NNUE
   if (useNNUE && !useClassical)
   {
-       int complexity;
-       int scale      = 1048 + 109 * pos.non_pawn_material() / 5120;
-       Color stm      = pos.side_to_move();
+       int nnueComplexity;
+       int scale = 1092 + 106 * pos.non_pawn_material() / 5120;
        Value optimism = pos.this_thread()->optimism[stm];
-       Value psq      = (stm == WHITE ? 1 : -1) * eg_value(pos.psq_score());
-       Value nnue     = NNUE::evaluate(pos, true, &complexity);     // NNUE
 
-       complexity = (137 * complexity + 137 * abs(nnue - psq)) / 256;
-       optimism = optimism * (255 + complexity) / 256;
-       v = (nnue * scale + optimism * (scale - 848)) / 1024;
+       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;
 
        if (pos.is_chess960())
            v += fix_FRC(pos);
@@ -1120,6 +1124,10 @@ Value Eval::evaluate(const Position& pos) {
   // Guarantee evaluation does not hit the tablebase range
   v = std::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);
 
+  // When not using NNUE, return classical complexity to caller
+  if (complexity && (!useNNUE || useClassical))
+       *complexity = abs(v - psq);
+
   return v;
 }