Simplify away nnue scale pawn count multiplier

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 12883fcc43e57a8a18f71e407f3604816a989321..873dc5d20693956bea19b72f07acc764a2c14008 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -1048,20 +1048,22 @@ make_v:
 
 Value Eval::evaluate(const Position& pos, int* complexity) {
 
+  assert(!pos.checkers());
+
   Value v;
   Value psq = pos.psq_eg_stm();
 
   // We use the much less accurate but faster Classical eval when the NNUE
   // option is set to false. Otherwise we use the NNUE eval unless the
-  // PSQ advantage is decisive and several pieces remain. (~3 Elo)
-  bool useClassical = !useNNUE || (pos.count<ALL_PIECES>() > 7 && abs(psq) > 1781);
+  // PSQ advantage is decisive. (~4 Elo at STC, 1 Elo at LTC)
+  bool useClassical = !useNNUE || abs(psq) > 2048;
 
   if (useClassical)
       v = Evaluation<NO_TRACE>(pos).value();
   else
   {
       int nnueComplexity;
-      int scale = 1001 + 5 * pos.count<PAWN>() + 61 * pos.non_pawn_material() / 4096;
+      int scale = 1001 + pos.non_pawn_material() / 64;
 
       Color stm = pos.side_to_move();
       Value optimism = pos.this_thread()->optimism[stm];