Fix PFC on root level elements

src/t8_forest/t8_forest_pfc_message.hxx

@@ -212,14 +212,18 @@ struct t8_forest_pfc_message
     scheme = t8_forest_get_scheme (forest);
     eclass = t8_forest_get_eclass (forest, t8_forest_get_local_id (forest, itree));
 
+    // Allocate memory for the parent element.
+    t8_element_new (scheme, eclass, 1, &parent);
+
     // If we are already the root element, we cannot be part of a split family, so we send any(the root) element and no num_siblings.
     if (scheme->element_get_level (eclass, element_closest_to_receiver) == 0) {
-      parent = element_closest_to_receiver;
+      // Copy the root element to the allocated parent element.
+      scheme->element_copy (eclass, element_closest_to_receiver, parent);
+      // Set the number of siblings to zero, since there are none on the root level.
       num_siblings = 0;
     }
     else {
       // Compute parent.
-      t8_element_new (scheme, eclass, 1, &parent);
       scheme->element_get_parent (eclass, element_closest_to_receiver, parent);
 
       // Distinguish send "direction"

test/t8_cmesh_generator/t8_cmesh_example_sets.hxx

@@ -63,6 +63,20 @@ auto pretty_print_base_example_scheme = [] (const testing::TestParamInfo<std::tu
   return name;
 };
 
+/** Define a lambda to beautify gtest output for tuples <scheme, level, cmesh>.
+ * Intended as a lambda to pass to an INSTANTIATE_TEST_SUITE_P
+ * to print the current scheme, level and \ref cmesh_example_base. */
+auto pretty_print_level_and_cmesh_params
+  = [] (const testing::TestParamInfo<std::tuple<int, int, cmesh_example_base *>> &info) {
+      std::string name = std::string ("Level_") + std::to_string (std::get<1> (info.param));
+      std::string cmesh_name;
+      std::get<2> (info.param)->param_to_string (cmesh_name);
+      name += std::string ("_") + cmesh_name;
+      name += std::string ("scheme_") + std::to_string (std::get<0> (info.param));
+      name += std::string ("_") + std::to_string (info.index);
+      return name;
+    };
+
 namespace cmesh_list
 {
 /** Vector of all example cmesh sets. */

test/t8_forest/t8_gtest_element_is_leaf.cxx

@@ -181,19 +181,6 @@ TEST_P (element_is_leaf_or_ghost, element_is_ghost_adapt)
   t8_test_element_is_leaf_for_forest (forest_adapt);
 }
 
-/* Define a lambda to beautify gtest output for tuples <scheme, level, cmesh>.
- * This will set the correct scheme, level and cmesh name as part of the test case name. */
-auto pretty_print_level_and_cmesh_params
-  = [] (const testing::TestParamInfo<std::tuple<int, int, cmesh_example_base *>> &info) {
-      std::string name = std::string ("Level_") + std::to_string (std::get<1> (info.param));
-      std::string cmesh_name;
-      std::get<2> (info.param)->param_to_string (cmesh_name);
-      name += std::string ("_") + cmesh_name;
-      name += std::string ("scheme_") + std::to_string (std::get<0> (info.param));
-      name += std::string ("_") + std::to_string (info.index);
-      return name;
-    };
-
 INSTANTIATE_TEST_SUITE_P (t8_gtest_element_is_leaf_or_ghost, element_is_leaf_or_ghost,
                           testing::Combine (AllSchemeCollections, testing::Range (0, T8_IS_LEAF_MAX_LVL),
                                             AllCmeshsParam),

test/t8_forest/t8_gtest_partition_for_coarsening.cxx

@@ -126,14 +126,14 @@ coarsen_all_callback ([[maybe_unused]] t8_forest_t forest, [[maybe_unused]] t8_f
                       const int is_family, [[maybe_unused]] const int num_elements,
                       [[maybe_unused]] t8_element_t *elements[])
 {
-  // Coarsen revery family.
+  // Coarsen every family.
   return (is_family ? -1 : 0);
 }
 
 /**
  * Class to test the partition-for-coarsening functionality.
 */
-struct t8_test_partition_for_coarsening_test: public testing::TestWithParam<std::tuple<int, cmesh_example_base *>>
+struct t8_test_partition_for_coarsening_test: public testing::TestWithParam<std::tuple<int, int, cmesh_example_base *>>
 {
 
  protected:
@@ -145,9 +145,12 @@ struct t8_test_partition_for_coarsening_test: public testing::TestWithParam<std:
     const int scheme_id = std::get<0> (GetParam ());
     scheme = create_from_scheme_id (scheme_id);
 
+    // Get the initial uniform refinement level.
+    level = std::get<1> (GetParam ());
+
     // Construct cmesh and store name.
-    cmesh = std::get<1> (GetParam ())->cmesh_create ();
-    cmesh_name = std::get<1> (GetParam ())->name;
+    cmesh = std::get<2> (GetParam ())->cmesh_create ();
+    cmesh_name = std::get<2> (GetParam ())->name;
 
     // Skip empty meshes.
     if (t8_cmesh_is_empty (cmesh)) {
@@ -200,6 +203,7 @@ struct t8_test_partition_for_coarsening_test: public testing::TestWithParam<std:
 
   // Member variables: The currently tested scheme and eclass.
   const t8_scheme *scheme; /**< The currently tested scheme. */
+  int level;               /**< The currently initial uniform refinement level. */
   t8_cmesh_t cmesh;        /**< The currently tested cmesh. */
   std::string cmesh_name;  /**< Name of the currently tested cmesh.*/
 };
@@ -213,9 +217,6 @@ TEST_P (t8_test_partition_for_coarsening_test, test_partition_for_coarsening)
   // -------------------------------------------
   t8_global_productionf ("Create uniform forest.\n");
 
-  // Initial uniform refinement level
-  const int level = 2;
-
   // Increase reference counters of cmesh and scheme to avoid reaching zero.
   t8_cmesh_ref (cmesh);
   scheme->ref ();
@@ -233,8 +234,18 @@ TEST_P (t8_test_partition_for_coarsening_test, test_partition_for_coarsening)
   // -----------------------------------------------------------
   t8_global_productionf ("Adapt uniform forest.\n");
 
-  // Create adapted base forest.
-  t8_forest_t adapted_base_forest = t8_forest_new_adapt (uniform_forest, refine_some_callback, 0, 0, nullptr);
+  // In some cases, we will adapt the uniform base forest.
+  t8_forest_t adapted_base_forest;
+
+  /* Ensure that in case of the root level test there is no adaptation, such that the partition bound will 
+  * definitely fall upon a root level element and the corresponding code section is covered. */
+  if (level != 0) {
+    // In any other case, we perform some adaptation.
+    adapted_base_forest = t8_forest_new_adapt (uniform_forest, refine_some_callback, 0, 0, nullptr);
+  }
+  else {
+    adapted_base_forest = uniform_forest;
+  }
 
 #if T8_ENABLE_DEBUG
   // If debug mode and an additional manual flag are set, write forest to vtk.
@@ -331,4 +342,5 @@ TEST_P (t8_test_partition_for_coarsening_test, test_partition_for_coarsening)
 
 // Instantiate parameterized test to be run for all schemes.
 INSTANTIATE_TEST_SUITE_P (t8_gtest_partition_for_coarsening, t8_test_partition_for_coarsening_test,
-                          testing::Combine (AllSchemeCollections, AllCmeshsParam), pretty_print_base_example_scheme);
+                          testing::Combine (AllSchemeCollections, testing::Values (0, 2), AllCmeshsParam),
+                          pretty_print_level_and_cmesh_params);