Double probability of using classical eval

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index db8379da34f8652bae813885629f91e9332e8a26..faf71d2701dd83ad152e2d82f260750a904e5809 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -1015,10 +1015,13 @@ 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
                 ||  useClassical
-                || (abs(eg_value(pos.psq_score())) > PawnValueMg / 8 && !(pos.this_thread()->nodes & 0xF));
+                || (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;