Changed a option name more descriptive, "Training" -> "PruneAtShallowDepthOnPvNode". The default value was changed but the default behavior is not changed.

Changed to set a global option prune_at_shallow_depth_on_pv_node on a callback function.

src/search.cpp

@@ -54,6 +54,10 @@ using std::string;
 using Eval::evaluate;
 using namespace Search;
 
+#if defined(EVAL_LEARN)
+bool Search::prune_at_shallow_depth_on_pv_node = false;
+#endif
+
 namespace {
 
   // Different node types, used as a template parameter
@@ -68,8 +72,6 @@ namespace {
     return Value(223 * (d - improving));
   }
 
-  bool training;
-
   // Reductions lookup table, initialized at startup
   int Reductions[MAX_MOVES]; // [depth or moveNumber]
 
@@ -195,8 +197,6 @@ void Search::init() {
 
   for (int i = 1; i < MAX_MOVES; ++i)
       Reductions[i] = int((22.0 + std::log(Threads.size())) * std::log(i));
-
-  training = Options["Training"];
 }
 
 
@@ -1011,7 +1011,9 @@ moves_loop: // When in check, search starts from here
 
       // Step 12. Pruning at shallow depth (~200 Elo)
       if (  !rootNode
-          && !(training && PvNode)
+#ifdef EVAL_LEARN
+          && !(!prune_at_shallow_depth_on_pv_node && PvNode)
+#endif
           && pos.non_pawn_material(us)
           && bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
       {

src/search.h

@@ -33,6 +33,10 @@ namespace Search {
 constexpr int CounterMovePruneThreshold = 0;
 
 
+#if defined(EVAL_LEARN)
+extern bool prune_at_shallow_depth_on_pv_node;
+#endif
+
 /// Stack struct keeps track of the information we need to remember from nodes
 /// shallower and deeper in the tree during the search. Each search thread has
 /// its own array of Stack objects, indexed by the current ply.

src/ucioption.cpp

@@ -42,6 +42,11 @@ void on_threads(const Option& o) { Threads.set(size_t(o)); }
 void on_tb_path(const Option& o) { Tablebases::init(o); }
 void on_use_NNUE(const Option& ) { Eval::init_NNUE(); }
 void on_eval_file(const Option& ) { Eval::init_NNUE(); }
+#ifdef EVAL_LEARN
+void on_prune_at_shallow_depth_on_pv_node(const Option& o) {
+  Search::prune_at_shallow_depth_on_pv_node = o;
+}
+#endif
 
 /// Our case insensitive less() function as required by UCI protocol
 bool CaseInsensitiveLess::operator() (const string& s1, const string& s2) const {
@@ -69,7 +74,6 @@ void init(OptionsMap& o) {
   o["Move Overhead"]         << Option(10, 0, 5000);
   o["Slow Mover"]            << Option(100, 10, 1000);
   o["nodestime"]             << Option(0, 0, 10000);
-  o["Training"]              << Option(false);
   o["UCI_Chess960"]          << Option(false);
   o["UCI_AnalyseMode"]       << Option(false);
   o["UCI_LimitStrength"]     << Option(false);
@@ -96,6 +100,8 @@ void init(OptionsMap& o) {
   // Evalsave by default. This folder shall be prepared in advance.
   // Automatically create a folder under this folder like "0/", "1/", ... and save the evaluation function file there.
   o["EvalSaveDir"] << Option("evalsave");
+  // Prune at shallow depth on PV nodes. Setting this value to true gains elo in shallow search.
+  o["PruneAtShallowDepthOnPvNode"] << Option(false, on_prune_at_shallow_depth_on_pv_node);
 #endif
 }