Fix code base on Roy's feedback

(a) Revert periodic BC source file
(b) Fix indentation in UnstructuredMesh::find_neighbors and wrap tests (c) involving solve() in DisconnectedNeighborTest with #ifdef LIBMESH_HAVE_SOLVER guards to ensure correct conditional compilation.

Author: ChengHauYang

src/base/periodic_boundaries.C

@@ -80,7 +80,6 @@ const Elem * PeriodicBoundaries::neighbor(boundary_id_type boundary_id,
   const MeshBase & mesh = point_locator.get_mesh();
   for(const Elem * elem_it : candidate_elements)
     {
-
       std::vector<unsigned int> neigh_sides =
         mesh.get_boundary_info().sides_with_boundary_id(elem_it, b->pairedboundary);
 
@@ -106,13 +105,14 @@ const Elem * PeriodicBoundaries::neighbor(boundary_id_type boundary_id,
   // either we're on a ghosted element with a remote periodic neighbor
   // or we're on a mesh with an inconsistent periodic boundary.
   libmesh_error_msg_if(mesh.is_serial() ||
-                      (e->processor_id() == mesh.processor_id()),
-                      "Periodic boundary neighbor not found");
+                       (e->processor_id() == mesh.processor_id()),
+                       "Periodic boundary neighbor not found");
 
   if (neigh_side)
     *neigh_side = libMesh::invalid_uint;
   return remote_elem;
 }
+
 } // namespace libMesh
 
 

src/mesh/unstructured_mesh.C

@@ -1015,13 +1015,15 @@ void UnstructuredMesh::find_neighbors (const bool reset_remote_elements,
                   element->neighbor_ptr(ms) != remote_elem)
                 continue;
 
-                for (const auto & [id, boundary_ptr] : *db)
+              for (const auto & [id, boundary_ptr] : *db)
                 {
                   if (!this->get_boundary_info().has_boundary_id(element, ms, id))
                     continue;
 
                   unsigned int neigh_side;
-                  const Elem * neigh = db->neighbor(id, *point_locator, element, ms, &neigh_side);
+                  const Elem * neigh =
+                    db->neighbor(id, *point_locator, element, ms, &neigh_side);
+
                   if (neigh && neigh != remote_elem && neigh != element)
                     {
                       element->set_neighbor(ms, this->elem_ptr(neigh->id()));

tests/systems/disconnected_neighbor_test.C

@@ -168,11 +168,14 @@ void assemble_temperature_jump(EquationSystems &es,
 class DisconnectedNeighborTest : public CppUnit::TestCase {
 public:
   LIBMESH_CPPUNIT_TEST_SUITE( DisconnectedNeighborTest );
+#ifdef LIBMESH_HAVE_SOLVER
   CPPUNIT_TEST( testTempJump );
+#endif
   CPPUNIT_TEST_SUITE_END();
 
 private:
 
+#ifdef LIBMESH_HAVE_SOLVER
   void testTempJump()
   {
     Mesh mesh(*TestCommWorld, 2);
@@ -241,7 +244,7 @@ private:
 
     // This is the key testing step: inform libMesh about the disconnected boundaries
     // And, in `prepare_for_use()`, libMesh will set up the disconnected neighbor relationships.
-    mesh.add_disconnected_boundaries(interface_left_id, interface_right_id);
+    mesh.add_disconnected_boundaries(interface_left_id, interface_right_id, RealVectorValue(0.0, 0.0, 0.0));
 
     // libMesh shouldn't renumber, or our based-on-initial-id
     // assertions later may fail.
@@ -299,6 +302,7 @@ private:
           LIBMESH_ASSERT_NUMBERS_EQUAL(exact, approx, 1e-2);
         }
   }
+#endif
 };
 
 CPPUNIT_TEST_SUITE_REGISTRATION( DisconnectedNeighborTest );