graph: allow access to native graph object

The native graph objects should be accessible for advanced users.

core/src/Cuda/Kokkos_Cuda_Graph_Impl.hpp

@@ -200,6 +200,9 @@ struct GraphImpl<Kokkos::Cuda> {
         m_execution_space, _graph_node_kernel_ctor_tag{},
         aggregate_kernel_impl_t{});
   }
+
+  cudaGraph_t& get_cuda_graph() { return m_graph; }
+  cudaGraphExec_t& get_cuda_graph_exec() { return m_graph_exec; }
 };
 
 }  // end namespace Impl

core/src/HIP/Kokkos_HIP_Graph_Impl.hpp

@@ -69,6 +69,9 @@ class GraphImpl<Kokkos::HIP> {
   template <class... PredecessorRefs>
   auto create_aggregate_ptr(PredecessorRefs&&...);
 
+  hipGraph_t& get_hip_graph() { return m_graph; }
+  hipGraphExec_t& get_hip_graph_exec() { return m_graph_exec; }
+
  private:
   void instantiate_graph() {
     constexpr size_t error_log_size = 256;

core/unit_test/CMakeLists.txt

@@ -828,7 +828,7 @@ if(Kokkos_ENABLE_HIP)
       hip/TestHIP_InterOp_Streams.cpp
   )
   KOKKOS_ADD_EXECUTABLE_AND_TEST(
-    UnitTest_HIPGraph
+    CoreUnitTest_HIPGraph
     SOURCES
       UnitTestMainInit.cpp
       hip/TestHIP_Graph.cpp

core/unit_test/cuda/TestCuda_Graph.cpp

@@ -16,3 +16,67 @@
 
 #include <TestCuda_Category.hpp>
 #include <TestGraph.hpp>
+
+namespace Test {
+
+/**
+ * @test This test ensures that the underlying @c CUDA objects can be retrieved
+ *       from a @c Kokkos::Graph.
+ *
+ * It also ensures that these objects can be modified "externally", thereby
+ * testing "interoperability".
+ */
+TEST(TEST_CATEGORY, cuda_graph_instantiate_and_debug_dot_print) {
+  //! Build a rank-1 zero-initialized view.
+  using view_t   = Kokkos::View<int, TEST_EXECSPACE>;
+  using view_h_t = Kokkos::View<int, Kokkos::HostSpace>;
+  view_t data("witness");
+
+  //! Build a graph, whose sole node will apply @ref AddOne on @ref data.
+  auto graph =
+      Kokkos::Experimental::create_graph<TEST_EXECSPACE>([&](auto root) {
+        root.then_parallel_for(
+            1, SetViewToValueFunctor<TEST_EXECSPACE, int>{data, 1});
+      });
+
+  //! Retrieve the @c Kokkos::Impl::Graph.
+  auto root_node_ref = Kokkos::Impl::GraphAccess::create_root_ref(graph);
+  auto graph_ptr_impl =
+      Kokkos::Impl::GraphAccess::get_graph_weak_ptr(root_node_ref).lock();
+
+  /// At this stage, the @c Cuda "executable" graph is null
+  /// because it has not been instantiated.
+  ASSERT_EQ(graph_ptr_impl->get_cuda_graph_exec(), nullptr);
+
+  //! Instantiate the graph manually.
+  constexpr size_t error_log_size = 256;
+  cudaGraphNode_t error_node      = nullptr;
+  char error_log[error_log_size];
+  cudaGraphInstantiate(&graph_ptr_impl->get_cuda_graph_exec(),
+                       graph_ptr_impl->get_cuda_graph(), &error_node, error_log,
+                       error_log_size);
+  ASSERT_EQ(error_node, nullptr) << error_log;
+
+  /// At this stage, the @c Cuda "executable" graph should not be null,
+  /// because it has been instantiated.
+  ASSERT_NE(graph_ptr_impl->get_cuda_graph_exec(), nullptr);
+  const cudaGraphExec_t manual = graph_ptr_impl->get_cuda_graph_exec();
+
+  /// Submit the graph through @c Kokkos::Graph API.
+  /// Note that @c Kokkos::Graph::submit should not modify the
+  /// @c cudaGraphExec_t object because we instantiated the graph manually.
+  graph.submit();
+
+  ASSERT_EQ(graph_ptr_impl->get_cuda_graph_exec(), manual);
+
+  //! The view has been modified and contains a one.
+  view_h_t data_h("witness on host");
+  Kokkos::deep_copy(graph.get_execution_space(), data_h, data);
+  ASSERT_EQ(data_h(), 1);
+
+  //! Export the graph structure as a DOT graph.
+  cudaGraphDebugDotPrint(graph_ptr_impl->get_cuda_graph(), "cuda_graph.dot",
+                         cudaGraphDebugDotFlagsVerbose);
+}
+
+}  // namespace Test

core/unit_test/hip/TestHIP_Graph.cpp

@@ -16,3 +16,69 @@
 
 #include <TestHIP_Category.hpp>
 #include <TestGraph.hpp>
+
+namespace Test {
+
+/**
+ * @test This test ensures that the underlying @c HIP objects can be retrieved
+ *       from a @c Kokkos::Graph.
+ *
+ * It also ensures that these objects can be modified "externally", thereby
+ * testing "interoperability".
+ */
+TEST(TEST_CATEGORY, hip_graph_instantiate_and_debug_dot_print) {
+  //! Build a rank-1 zero-initialized view.
+  using view_t   = Kokkos::View<int, TEST_EXECSPACE>;
+  using view_h_t = Kokkos::View<int, Kokkos::HostSpace>;
+  view_t data("witness");
+
+  //! Build a graph, whose sole node will apply @ref AddOne on @ref data.
+  auto graph =
+      Kokkos::Experimental::create_graph<TEST_EXECSPACE>([&](auto root) {
+        root.then_parallel_for(
+            1, SetViewToValueFunctor<TEST_EXECSPACE, int>{data, 1});
+      });
+
+  //! Retrieve the @c Kokkos::Impl::Graph.
+  auto root_node_ref = Kokkos::Impl::GraphAccess::create_root_ref(graph);
+  auto graph_ptr_impl =
+      Kokkos::Impl::GraphAccess::get_graph_weak_ptr(root_node_ref).lock();
+
+  /// At this stage, the @c HIP "executable" graph is null
+  /// because it has not been instantiated.
+  ASSERT_EQ(graph_ptr_impl->get_hip_graph_exec(), nullptr);
+
+  //! Instantiate the graph manually.
+  constexpr size_t error_log_size = 256;
+  hipGraphNode_t error_node       = nullptr;
+  char error_log[error_log_size];
+  KOKKOS_IMPL_HIP_SAFE_CALL(hipGraphInstantiate(
+      &graph_ptr_impl->get_hip_graph_exec(),
+      graph_ptr_impl->get_hip_graph(), &error_node, error_log,
+      error_log_size));
+  ASSERT_EQ(error_node, nullptr) << error_log;
+
+  /// At this stage, the @c HIP "executable" graph should not be null,
+  /// because it has been instantiated.
+  ASSERT_NE(graph_ptr_impl->get_hip_graph_exec(), nullptr);
+  const hipGraphExec_t manual = graph_ptr_impl->get_hip_graph_exec();
+
+  /// Submit the graph through @c Kokkos::Graph API.
+  /// Note that @c Kokkos::Graph::submit should not modify the @c hipGraphExec_t
+  /// object because we instantiated the graph manually.
+  graph.submit();
+
+  ASSERT_EQ(graph_ptr_impl->get_hip_graph_exec(), manual);
+
+  //! The view has been modified and contains a one.
+  view_h_t data_h("witness on host");
+  Kokkos::deep_copy(graph.get_execution_space(), data_h, data);
+  ASSERT_EQ(data_h(), 1);
+
+  //! Export the graph structure as a DOT graph.
+  KOKKOS_IMPL_HIP_SAFE_CALL(
+      hipGraphDebugDotPrint(graph_ptr_impl->get_hip_graph(), "hip_graph.dot",
+                            hipGraphDebugDotFlagsVerbose));
+}
+
+}  // namespace Test