Use per-thread dynamic contempt

src/evaluate.cpp

@@ -28,8 +28,7 @@
 #include "evaluate.h"
 #include "material.h"
 #include "pawns.h"
-
-std::atomic<Score> Eval::Contempt;
+#include "thread.h"
 
 namespace Trace {
 
@@ -844,7 +843,7 @@ namespace {
     // Initialize score by reading the incrementally updated scores included in
     // the position object (material + piece square tables) and the material
     // imbalance. Score is computed internally from the white point of view.
-    Score score = pos.psq_score() + me->imbalance() + Eval::Contempt;
+    Score score = pos.psq_score() + me->imbalance() + pos.this_thread()->contemptScore;
 
     // Probe the pawn hash table
     pe = Pawns::probe(pos);
@@ -915,7 +914,7 @@ std::string Eval::trace(const Position& pos) {
 
   std::memset(scores, 0, sizeof(scores));
 
-  Eval::Contempt = SCORE_ZERO; // Reset any dynamic contempt
+  pos.this_thread()->contemptScore = SCORE_ZERO; // Reset any dynamic contempt
 
   Value v = Evaluation<TRACE>(pos).value();
 

src/evaluate.h

@@ -32,8 +32,6 @@ namespace Eval {
 
 constexpr Value Tempo = Value(20); // Must be visible to search
 
-extern std::atomic<Score> Contempt;
-
 std::string trace(const Position& pos);
 
 Value evaluate(const Position& pos);

src/search.cpp

@@ -309,8 +309,8 @@ void Thread::search() {
   multiPV = std::min(multiPV, rootMoves.size());
 
   int ct = Options["Contempt"] * PawnValueEg / 100; // From centipawns
-  Eval::Contempt = (us == WHITE ?  make_score(ct, ct / 2)
-                                : -make_score(ct, ct / 2));
+  contemptScore = (us == WHITE ?  make_score(ct, ct / 2)
+                               : -make_score(ct, ct / 2));
 
   // Iterative deepening loop until requested to stop or the target depth is reached
   while (   (rootDepth += ONE_PLY) < DEPTH_MAX
@@ -353,8 +353,8 @@ void Thread::search() {
               // Adjust contempt based on root move's previousScore (dynamic contempt)
               ct += int(std::round(48 * atan(float(previousScore) / 128)));
 
-              Eval::Contempt = (us == WHITE ?  make_score(ct, ct / 2)
-                                            : -make_score(ct, ct / 2));
+              contemptScore = (us == WHITE ?  make_score(ct, ct / 2)
+                                           : -make_score(ct, ct / 2));
           }
 
           // Start with a small aspiration window and, in the case of a fail

src/thread.h

@@ -71,6 +71,7 @@ class Thread {
   ButterflyHistory mainHistory;
   CapturePieceToHistory captureHistory;
   ContinuationHistory contHistory;
+  Score contemptScore;
 };