#672: docs: write doxygen for collectives

src/vt/collective/collective_alg.h

@@ -64,6 +64,15 @@ namespace vt { namespace collective {
 
 constexpr CollectiveAlgType const fst_collective_alg = 1;
 
+/**
+ * \struct CollectiveAlg
+ *
+ * \brief Perform asynchronous collectives within VT
+ *
+ * CollectiveAlg is a core VT component that provides the ability to perform
+ * reductions, scatters, barriers, and safe MPI (collective) operations while
+ * inside a VT handler.
+ */
 struct CollectiveAlg :
     runtime::component::Component<CollectiveAlg>,
     virtual reduce::ReduceManager,

src/vt/collective/collective_scope.h

@@ -82,6 +82,18 @@ struct ScopeImpl {
 
 } /* end namespace detail */
 
+/**
+ * \struct CollectiveScope
+ *
+ * \brief A distinct scope for enqueuing ordered collective operations.
+ *
+ * Each collective scope builds an individual sequence of collective operations
+ * that get orchestrated across nodes using a consensus algorithm so all nodes
+ * agree on a particular operation to execute in the sequence.
+ *
+ * This enables one to execute blocking MPI collectives inside VT handlers
+ * without causing progress to halt due to asynchrony.
+ */
 struct CollectiveScope {
 
 private: