Add select_nn_index() for phase selection (#216)

- return 0 if no phases is enabled

Set Game_Phase_Definition default to "lichess"

engine/src/searchthread.cpp

@@ -379,27 +379,35 @@ void SearchThread::create_mini_batch()
     }
 }
 
+size_t SearchThread::select_nn_index()
+{
+    if (nets.size() == 1) {
+        return 0;
+    }
+    // determine majority class in current batch
+    using pair_type = decltype(phaseCountMap)::value_type;
+    auto pr = std::max_element
+    (
+        std::begin(phaseCountMap), std::end(phaseCountMap),
+        [](const pair_type& p1, const pair_type& p2) {
+            return p1.second < p2.second;
+        }
+    );
+
+    GamePhase majorityPhase = pr->first;
+
+    phaseCountMap.clear();
+    return phaseToNetsIndex.at(majorityPhase);
+}
+
 void SearchThread::thread_iteration()
 {
     create_mini_batch();
 #ifndef SEARCH_UCT
     if (newNodes->size() != 0) {
-
-        // determine majority class in current batch
-        using pair_type = decltype(phaseCountMap)::value_type;
-        auto pr = std::max_element
-        (
-            std::begin(phaseCountMap), std::end(phaseCountMap),
-            [](const pair_type& p1, const pair_type& p2) {
-                return p1.second < p2.second;
-            }
-        );
-
-        GamePhase majorityPhase = pr->first;
 
-        phaseCountMap.clear();
         // query the network that corresponds to the majority phase
-        nets[phaseToNetsIndex.at(majorityPhase)]->predict(inputPlanes, valueOutputs, probOutputs, auxiliaryOutputs);
+        nets[select_nn_index()]->predict(inputPlanes, valueOutputs, probOutputs, auxiliaryOutputs);
         set_nn_results_to_child_nodes();
     }
 #endif

engine/src/searchthread.h

@@ -196,6 +196,13 @@ class SearchThread : public NeuralNetAPIUser
      * @return Q-Value converted to double
      */
     double get_current_transposition_q_value(const Node* currentNode, ChildIdx childIdx, uint_fast32_t transposVisits);
+
+    /**
+     * @brief select_nn_index Returns the index according to the majority phase in the current batch.
+     * If no phases is enabled, 0 will be returned.
+     * @return Majority phase index or 0
+     */
+    size_t select_nn_index();
 };
 
 void run_search_thread(SearchThread *t);

engine/src/uci/optionsuci.cpp

@@ -193,7 +193,7 @@ void OptionsUCI::init(OptionsMap &o)
     o["Use_Raw_Network"]               << Option(false);
     o["Virtual_Style"]                 << Option("virtual_mix", { "virtual_loss", "virtual_visit", "virtual_offset", "virtual_mix" });
     o["Virtual_Mix_Threshold"]         << Option(1000, 1, 99999999);
-    o["Game_Phase_Definition"]         << Option("movecount", { "lichess", "movecount"});
+    o["Game_Phase_Definition"]         << Option("lichess", { "lichess", "movecount"});
     // additional UCI-Options for RL only
 #ifdef USE_RL
     o["Centi_Node_Random_Factor"]      << Option(10, 0, 100);