Double probability of using classical eval

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 67154751f2ad97a40d4f53f4e5966b003312ef08..faf71d2701dd83ad152e2d82f260750a904e5809 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -227,26 +227,26 @@ namespace {
 
   // Outpost[knight/bishop] contains bonuses for each knight or bishop occupying a
   // pawn protected square on rank 4 to 6 which is also safe from a pawn attack.
-  constexpr Score Outpost[] = { S(56, 36), S(30, 23) };
+  constexpr Score Outpost[] = { S(56, 34), S(31, 23) };
 
   // PassedRank[Rank] contains a bonus according to the rank of a passed pawn
   constexpr Score PassedRank[RANK_NB] = {
-    S(0, 0), S(10, 28), S(17, 33), S(15, 41), S(62, 72), S(168, 177), S(276, 260)
+    S(0, 0), S(9, 28), S(15, 31), S(17, 39), S(64, 70), S(171, 177), S(277, 260)
   };
 
   // RookOnFile[semiopen/open] contains bonuses for each rook when there is
   // no (friendly) pawn on the rook file.
-  constexpr Score RookOnFile[] = { S(19, 7), S(48, 29) };
+  constexpr Score RookOnFile[] = { S(19, 7), S(48, 27) };
 
   // ThreatByMinor/ByRook[attacked PieceType] contains bonuses according to
   // which piece type attacks which one. Attacks on lesser pieces which are
   // pawn-defended are not considered.
   constexpr Score ThreatByMinor[PIECE_TYPE_NB] = {
-    S(0, 0), S(5, 32), S(57, 41), S(77, 56), S(88, 119), S(79, 161)
+    S(0, 0), S(5, 32), S(55, 41), S(77, 56), S(89, 119), S(79, 162)
   };
 
   constexpr Score ThreatByRook[PIECE_TYPE_NB] = {
-    S(0, 0), S(3, 46), S(37, 68), S(42, 60), S(0, 38), S(58, 41)
+    S(0, 0), S(3, 44), S(37, 68), S(42, 60), S(0, 39), S(58, 43)
   };
 
   // Assorted bonuses and penalties
@@ -1015,12 +1015,19 @@ make_v:
 
 Value Eval::evaluate(const Position& pos) {
 
+  // Use classical eval if there is a large imbalance
+  // If there is a moderate imbalance, use classical eval with probability (1/8),
+  // as derived from the node counter.
+  bool useClassical = abs(eg_value(pos.psq_score())) * 16 > NNUEThreshold1 * (16 + pos.rule50_count());
   bool classical = !Eval::useNNUE
-                ||  abs(eg_value(pos.psq_score())) * 16 > NNUEThreshold1 * (16 + pos.rule50_count());
+                ||  useClassical
+                || (abs(eg_value(pos.psq_score())) > PawnValueMg / 4 && !(pos.this_thread()->nodes & 0xB));
   Value v = classical ? Evaluation<NO_TRACE>(pos).value()
                       : NNUE::evaluate(pos) * 5 / 4 + Tempo;
 
-  if (classical && Eval::useNNUE && abs(v) * 16 < NNUEThreshold2 * (16 + pos.rule50_count()))
+  if (   useClassical 
+      && Eval::useNNUE 
+      && abs(v) * 16 < NNUEThreshold2 * (16 + pos.rule50_count()))
       v = NNUE::evaluate(pos) * 5 / 4 + Tempo;
 
   // Damp down the evaluation linearly when shuffling