#2094: Add unit tests for multicast

Author: JacobDomagala

examples/hello_world/objgroup.cc

@@ -60,7 +60,7 @@ int main(int argc, char** argv) {
   auto proxy =
     vt::theObjGroup()->makeCollective<MyObjGroup>("examples_hello_world");
 
-  // Create group of odd nodes and broadcast to them (from root node)
+  // Create group of odd nodes and multicast to them (from root node)
   vt::theGroup()->newGroupCollective(
     this_node % 2, [proxy, this_node](::vt::GroupType type) {
       if (this_node == 0) {
@@ -83,7 +83,7 @@ int main(int argc, char** argv) {
 
     using namespace ::vt::group::region;
 
-    // Create list of nodes and broadcast to them
+    // Create list of nodes and multicast to them
     List::ListType range;
     for (vt::NodeType node = 0; node < num_nodes; ++node) {
       if (node % 2 == 0) {

src/vt/group/group_manager.h

@@ -121,12 +121,22 @@ struct GroupManager : runtime::component::Component<GroupManager> {
    */
   void setupDefaultGroup();
 
-  void AddNewTempGroup(const region::Region::ListType& key, GroupType value) {
-    temporary_groups_[key] = value;
+  /**
+   * \internal \brief Cache group created by multicast. This allows for reusing the same group.
+   *
+   * \param[in] range list of nodes that are part of given group
+   * \param[in] group group to cache
+   */
+  void AddNewTempGroup(const region::Region::ListType& range, GroupType group) {
+    temporary_groups_[range] = group;
   }
 
+  /**
+   * \internal \brief Return (if any) group associated with given range of nodes
+   */
   std::optional<GroupType>
   GetTempGroupForRange(const region::Region::ListType& range);
+
   /**
    * \brief Create a new rooted group.
    *
@@ -438,7 +448,8 @@ struct GroupManager : runtime::component::Component<GroupManager> {
   ActionContainerType   continuation_actions_         = {};
   ActionListType        cleanup_actions_              = {};
   CollectiveScopeType   collective_scope_;
-  std::unordered_map<region::Region::ListType, GroupType, region::ListHash> temporary_groups_ = {};
+  std::unordered_map<region::Region::ListType, GroupType, region::ListHash>
+    temporary_groups_ = {};
 };
 
 /**

src/vt/objgroup/proxy/proxy_objgroup.impl.h

@@ -138,7 +138,11 @@ template <typename ObjT>
 template <auto f, typename... Params>
 typename Proxy<ObjT>::PendingSendType Proxy<ObjT>::multicast(
   group::region::Region::RegionUPtrType&& nodes, Params&&... params) const {
-  // This will work for list-type ranges only
+  vtAssert(
+    not dynamic_cast<group::region::ShallowList*>(nodes.get()),
+    "multicast: range of nodes is not supported for ShallowList!"
+  );
+
   nodes->sort();
   auto& range = nodes->makeList();
 

tests/unit/objgroup/test_objgroup.cc

@@ -289,6 +289,32 @@ TEST_F(TestObjGroup, test_proxy_invoke) {
   EXPECT_EQ(proxy.get()->recv_, 3);
 }
 
+TEST_F(TestObjGroup, test_proxy_multicast) {
+  using namespace ::vt::group::region;
+  auto const this_node = theContext()->getNode();
+  auto const num_nodes = theContext()->getNumNodes();
+
+  auto proxy =
+    vt::theObjGroup()->makeCollective<MyObjA>("test_proxy_multicast");
+
+  vt::runInEpochCollective([this_node, num_nodes, proxy] {
+    if (this_node == 0) {
+      // Create list of nodes and multicast to them
+      List::ListType range;
+      for (vt::NodeType node = 0; node < num_nodes; ++node) {
+        if (node % 2 == 0) {
+          range.push_back(node);
+        }
+      }
+
+      proxy.multicast<&MyObjA::handler>(std::make_unique<List>(range));
+    }
+  });
+
+  const auto expected = this_node % 2 == 0 ? 1 : 0;
+  EXPECT_EQ(proxy.get()->recv_, expected);
+}
+
 TEST_F(TestObjGroup, test_pending_send) {
   auto my_node = vt::theContext()->getNode();
   // create a proxy to a object group