#2387: trace: remove callback and refactor reduce call

Author: cwschilly

src/vt/pipe/callback/cb_union/cb_raw_base.fwd.h

@@ -59,4 +59,4 @@ using CallbackU = pipe::callback::cbunion::CallbackRawBaseSingle;
 
 } // end namespace vt
 
-#endif /*INCLUDED_VT_PIPE_CALLBACK_CB_UNION_CB_RAW_BASE_FWD_H*/
+#endif /*INCLUDED_VT_PIPE_CALLBACK_CB_UNION_CB_RAW_BASE_FWD_H*/

src/vt/trace/trace.cc

@@ -210,10 +210,13 @@ void Trace::addUserData(int32_t data) {
   );
 }
 
+void Trace::reducedEventsHan(UserEventRegistry gathered_user_events) {
+  vtAssert(theContext()->getNode() == 0, "Must be node 0");
+  user_event_ = gathered_user_events;
+}
+
 void Trace::gatherUserEvents() {
-  vt::runInEpochCollective([&]{
-    proxy_.reduce<vt::collective::PlusOp>(0, std::move(user_event_));
-  });
+  proxy_.reduce<&Trace::reducedEventsHan, vt::collective::PlusOp>(0, std::move(user_event_));
 }
 
 UserEventIDType Trace::registerUserEventRoot(std::string const& name) {

src/vt/trace/trace.h

@@ -291,6 +291,12 @@ struct Trace : runtime::component::Component<Trace>, TraceLite {
    */
   void addUserData(int32_t data);
 
+  /**
+   * \brief Update event registry on Node 0 with all gathered events
+   * \param[in] gathered_user_events summed registry of user events from all nodes
+   */
+  void reducedEventsHan(UserEventRegistry gathered_user_events);
+
   /**
    * \brief Gathers all user-defined event hashes onto node 0.
    */