#2387: trace: inherit virtual gather function from TraceLite

src/vt/trace/trace.cc

@@ -197,6 +197,12 @@ void Trace::addUserData(int32_t data) {
   );
 }
 
+void Trace::gatherUserEvents() {
+  vt::runInEpochCollective([&]{
+    proxy.reduce<vt::collective::PlusOp>(0, std::move(user_event_));
+  });
+}
+
 UserEventIDType Trace::registerUserEventRoot(std::string const& name) {
   return user_event_.rooted(name);
 }
@@ -519,6 +525,7 @@ void Trace::setTraceEnabledCurrentPhase(PhaseType cur_phase) {
       // Go ahead and perform a trace flush when tracing is disabled (and was
       // previously enabled) to reduce memory footprint.
       if (not ret and theConfig()->vt_trace_flush_size != 0) {
+        gatherUserEvents();
         writeTracesFile(incremental_flush_mode, true);
       }
     }

src/vt/trace/trace.h

@@ -287,6 +287,11 @@ struct Trace : runtime::component::Component<Trace>, TraceLite {
    */
   void addUserData(int32_t data);
 
+  /**
+   * \brief Gathers all user-defined event hashes onto node 0.
+   */
+  void gatherUserEvents() override;
+
   /**
    * \brief Log a memory usage event
    *

src/vt/trace/trace_lite.cc

@@ -543,10 +543,6 @@ void TraceLite::flushTracesFile(bool useGlobalSync) {
 void TraceLite::writeTracesFile(int flush, bool is_incremental_flush) {
   auto const node = theContext()->getNode();
 
-  vt::runInEpochCollective([&]{
-    proxy.reduce<vt::collective::PlusOp>(0, std::move(user_event_));
-  });
-
   size_t to_write = traces_.size();
 
   if (traceWritingEnabled(node) and to_write > 0) {

src/vt/trace/trace_lite.h

@@ -82,6 +82,11 @@ struct TraceLite  {
 
   virtual ~TraceLite();
 
+  /**
+   * \brief Gathers all user-defined event hashes onto node 0.
+   */
+  virtual void gatherUserEvents();
+
   /**
    * \brief Set zlib incremental flush mode for trace file.
    *

src/vt/trace/trace_user_event.cc

@@ -126,10 +126,10 @@ bool UserEventRegistry::insertEvent(
       std::forward_as_tuple(name)
     );
     return true;
-  } else {
+  } else if (user_event_[event] != name){
     user_event_[event] += " COLLISION " + name;
-    return false;
   }
+  return false;
 }
 
 UserEventRegistry operator+(

src/vt/trace/trace_user_event.h

@@ -123,6 +123,8 @@ struct UserEventRegistry {
 
   friend void insertNewUserEvent(UserEventIDType event, std::string const& name);
 
+  friend UserEventRegistry operator+(UserEventRegistry r1, UserEventRegistry const& r2);
+
   template <typename Serializer>
   void serialize(Serializer& s) {
     s | cur_root_event_