#276: Automatically synthesize message type in vt/group

Author: thearusable

src/vt/group/group_manager.h

@@ -193,6 +193,24 @@ struct GroupManager : runtime::component::Component<GroupManager> {
   template <typename MsgT, ActiveTypedFnType<MsgT> *f>
   void sendMsg(GroupType const group, MsgT* msg);
 
+  template <typename ReturnT, typename... Args>
+  struct FunctionTraits;
+
+  template <typename ReturnT, typename T>
+  struct FunctionTraits<ReturnT(*)(T*)> {
+    using MsgT = T;
+    using ReturnType = ReturnT;
+  };
+
+  template <auto f>
+  void sendMsg(
+    GroupType const group,
+    typename FunctionTraits<decltype(f)>::MsgT* msg
+  ) {
+    using MsgT = typename FunctionTraits<decltype(f)>::MsgT;
+    return sendMsg<MsgT, f>(group, msg);
+  }
+
   friend struct Info;
   friend struct InfoColl;
   friend struct FinishedWork;

src/vt/objgroup/manager.h

@@ -273,6 +273,34 @@ struct ObjGroupManager : runtime::component::Component<ObjGroupManager> {
     collective::reduce::ReduceStamp const& stamp
   );
 
+  template <typename ReturnT, typename... Args>
+  struct FunctionTraits;
+
+  template <typename ReturnT, typename T>
+  struct FunctionTraits<ReturnT(*)(T*)> {
+    using MsgT = T;
+    using ReturnType = ReturnT;
+  };
+
+  /**
+   * \brief Perform a reduction over an objgroup
+   *
+   * \param[in] proxy proxy to the object group
+   * \param[in] msg reduction message
+   * \param[in] stamp stamp to identify reduction across nodes
+   *
+   * \return the PendingSend corresponding to the reduce
+   */
+  template <typename ObjT, auto f>
+  PendingSendType reduce(
+    ProxyType<ObjT> proxy,
+    messaging::MsgPtrThief<typename FunctionTraits<decltype(f)>::MsgT> msg,
+    collective::reduce::ReduceStamp const& stamp
+  ) {
+    using MsgT = typename FunctionTraits<decltype(f)>::MsgT;
+    return reduce<ObjT, MsgT, f>(proxy, msg, stamp);
+  }
+
   /**
    * \brief Get a pointer to the local objgroup instance. Returns null if the
    * object doesn't exist.

src/vt/objgroup/manager.impl.h

@@ -271,7 +271,7 @@ ObjGroupManager::PendingSendType ObjGroupManager::reduce(
   auto const objgroup = proxy.getProxy();
 
   auto r = theCollective()->getReducerObjGroup(objgroup);
-  return r->template reduce<MsgT,f>(root, msg.get(), stamp);
+  return r->template reduce<f>(root, msg.get(), stamp);
 }
 
 template <typename ObjT>

src/vt/objgroup/proxy/proxy_objgroup_elm.h

@@ -213,6 +213,27 @@ struct ProxyElm<void> {
   template <typename MsgT, ActiveTypedFnType<MsgT>* f, typename... Args>
   void send(Args&&... args) const;
 
+  template <typename ReturnT, typename... Args>
+  struct FunctionTraits;
+
+  template <typename ReturnT, typename T>
+  struct FunctionTraits<ReturnT(*)(T*)> {
+    using MsgT = T;
+    using ReturnType = ReturnT;
+  };
+
+  /**
+   * \brief Send a message to the node indexed by this proxy to be
+   * delivered to the local object instance
+   *
+   * \param[in] args args to pass to the message constructor
+   */
+  template <auto f, typename... Args>
+  void send(Args&&... args) const {
+    using MsgT = typename FunctionTraits<decltype(f)>::MsgT;
+    send<MsgT, f>(std::forward<Args>(args)...);
+  }
+
 private:
   NodeType node_ = uninitialized_destination; /**< The indexed node */
 };