Avoid unnecessary string copies

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 71c4e8d15a987d9c4c6302feb75d8b76aaa706d7..6db977a4c7e2c636c82b4417b423daf0c2203470 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -1,6 +1,6 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
-  Copyright (C) 2004-2022 The Stockfish developers (see AUTHORS file)
+  Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -89,7 +89,7 @@ namespace Eval {
     vector<string> dirs = { "<internal>" , "" , CommandLine::binaryDirectory };
     #endif
 
-    for (string directory : dirs)
+    for (const string& directory : dirs)
         if (currentEvalFileName != eval_file)
         {
             if (directory != "<internal>")
@@ -159,24 +159,24 @@ namespace Trace {
 
   Score scores[TERM_NB][COLOR_NB];
 
-  double to_cp(Value v) { return double(v) / UCI::NormalizeToPawnValue; }
+  static double to_cp(Value v) { return double(v) / UCI::NormalizeToPawnValue; }
 
-  void add(int idx, Color c, Score s) {
+  static void add(int idx, Color c, Score s) {
     scores[idx][c] = s;
   }
 
-  void add(int idx, Score w, Score b = SCORE_ZERO) {
+  static void add(int idx, Score w, Score b = SCORE_ZERO) {
     scores[idx][WHITE] = w;
     scores[idx][BLACK] = b;
   }
 
-  std::ostream& operator<<(std::ostream& os, Score s) {
+  static std::ostream& operator<<(std::ostream& os, Score s) {
     os << std::setw(5) << to_cp(mg_value(s)) << " "
        << std::setw(5) << to_cp(eg_value(s));
     return os;
   }
 
-  std::ostream& operator<<(std::ostream& os, Term t) {
+  static std::ostream& operator<<(std::ostream& os, Term t) {
 
     if (t == MATERIAL || t == IMBALANCE || t == WINNABLE || t == TOTAL)
         os << " ----  ----"    << " | " << " ----  ----";
@@ -1056,7 +1056,7 @@ Value Eval::evaluate(const Position& pos, int* complexity) {
   // 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) > 1760);
+  bool useClassical = !useNNUE || (pos.count<ALL_PIECES>() > 7 && abs(psq) > 1781);
 
   if (useClassical)
       v = Evaluation<NO_TRACE>(pos).value();
@@ -1071,21 +1071,21 @@ Value Eval::evaluate(const Position& pos, int* complexity) {
       Value nnue = NNUE::evaluate(pos, true, &nnueComplexity);
 
       // Blend nnue complexity with (semi)classical complexity
-      nnueComplexity = (  412 * nnueComplexity
-                        + 428 * abs(psq - nnue)
+      nnueComplexity = (  406 * nnueComplexity
+                        + 424 * abs(psq - nnue)
                         + (optimism  > 0 ? int(optimism) * int(psq - nnue) : 0)
-                        ) / 1026;
+                        ) / 1024;
 
       // Return hybrid NNUE complexity to caller
       if (complexity)
           *complexity = nnueComplexity;
 
-      optimism = optimism * (278 + nnueComplexity) / 256;
-      v = (nnue * scale + optimism * (scale - 755)) / 1024;
+      optimism = optimism * (272 + nnueComplexity) / 256;
+      v = (nnue * scale + optimism * (scale - 748)) / 1024;
   }
 
   // Damp down the evaluation linearly when shuffling
-  v = v * (197 - pos.rule50_count()) / 214;
+  v = v * (200 - pos.rule50_count()) / 214;
 
   // 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);