Remove boundary deletion upon child boundary transfer.

src/mesh/boundary_info.C

@@ -1890,12 +1890,8 @@ BoundaryInfo::transfer_boundary_ids_from_children(const Elem * const parent)
     // This is where the decision is made. If 50% of the children have the tags,
     // we propagate them upwards upon coarsening. Otherwise, they are deleted.
     for (const auto & boundary : boundary_counts)
-    {
       if (boundary.second / number_of_sides_on_children > 0.5)
         this->add_side(parent, side_i, boundary.first);
-      else
-        this->remove_side(parent, side_i, boundary.first);
-    }
   }
 
   for (const auto & child_i : make_range(parent->n_children()))

src/mesh/mesh_refinement.C

@@ -1370,9 +1370,8 @@ bool MeshRefinement::_coarsen_elements ()
 
   for (auto & elem : _mesh.element_ptr_range())
     {
-      // Make sure we transfer the element's boundary id(s)
+      // Make sure we transfer the children's boundary id(s)
       // up to its parent when necessary before coarsening.
-      // This can be adding or removing the corresonding boundary info.
       _mesh.get_boundary_info().transfer_boundary_ids_from_children(elem);
 
       // active elements flagged for coarsening will
@@ -1388,11 +1387,11 @@ bool MeshRefinement::_coarsen_elements ()
           elem->nullify_neighbors();
 
           // Remove any boundary information associated
-          // with this element if we do not allow children to have boundary info
-          // otherwise we will have trouble in boundary info consistency among
-          // parent and children elements
-          // if (!_mesh.get_boundary_info().is_children_on_boundary_side())
-          _mesh.get_boundary_info().remove (elem);
+          // with this element if we do not allow children to have boundary info.
+          // Otherwise, we will do the removal in `transfer_boundary_ids_from_children`
+          // to make sure we don't delete the information before it is transferred
+          if (!_mesh.get_boundary_info().is_children_on_boundary_side())
+            _mesh.get_boundary_info().remove (elem);
 
           // Add this iterator to the _unused_elements
           // data structure so we might fill it.

tests/mesh/boundary_info.C

@@ -560,6 +560,8 @@ public:
       if (c(0) < 1)
       {
         CPPUNIT_ASSERT(bi.has_boundary_id(elem, 1, 5));
+        // We clean up this boundary ID for the next round of tests
+        bi.remove_side(elem, 1, 5);
         // we will refine this element again
         elem->set_refinement_flag(Elem::REFINE);
       }