Add preparation flag related to sub id to name map

include/mesh/mesh_base.h

@@ -340,6 +340,16 @@ class MeshBase : public ParallelObject
   void unset_has_boundary_id_sets()
   { _preparation.has_boundary_id_sets = false; }
 
+  /**
+   * Tells this we have done some operation which may have left the
+   * subdomain id to name map inconsistent across processors.
+   *
+   * User code which adds or changes subdomain names should call this
+   * method.
+   */
+  void unset_has_synched_subdomain_name_map()
+  { _preparation.has_synched_subdomain_name_map = false; }
+
   /**
    * \returns \p true if all elements and nodes of the mesh
    * exist on the current processor, \p false otherwise
@@ -1892,7 +1902,7 @@ class MeshBase : public ParallelObject
    * \returns A writable reference to the whole subdomain name map
    */
   std::map<subdomain_id_type, std::string> & set_subdomain_name_map ()
-  { return _block_id_to_name; }
+  { this->unset_has_synched_subdomain_name_map(); return _block_id_to_name; }
   const std::map<subdomain_id_type, std::string> & get_subdomain_name_map () const
   { return _block_id_to_name; }
 
@@ -1988,7 +1998,9 @@ class MeshBase : public ParallelObject
    * subdomain ids, but distributed mesh generators may only know
    * about part of a mesh when creating names.  This method can
    * synchronize the subdomain id to name map across processors,
-   * assuming no conflicts exist.
+   * assuming no conflicts exist.  It is called automatically during
+   * complete_preparation() unless the map is already known to be
+   * synchronized.
    */
   void sync_subdomain_name_map();
 
@@ -2077,6 +2089,7 @@ class MeshBase : public ParallelObject
     bool has_removed_orphaned_nodes;
     bool has_boundary_id_sets;
     bool has_reinit_ghosting_functors;
+    bool has_synched_subdomain_name_map;
   };
 
 protected:

src/mesh/distributed_mesh.C

@@ -202,15 +202,15 @@ DistributedMesh::DistributedMesh (const MeshBase & other_mesh) :
 
   this->copy_constraint_rows(other_mesh);
 
-  this->_preparation = other_mesh.preparation();
-
   auto & this_boundary_info = this->get_boundary_info();
   const auto & other_boundary_info = other_mesh.get_boundary_info();
 
   this_boundary_info = other_boundary_info;
 
   this->set_subdomain_name_map() = other_mesh.get_subdomain_name_map();
 
+  this->_preparation = other_mesh.preparation();
+
 #ifdef LIBMESH_ENABLE_UNIQUE_ID
   _next_unique_id = other_mesh.parallel_max_unique_id() +
                     this->processor_id();

src/mesh/mesh_base.C

@@ -938,6 +938,13 @@ void MeshBase::complete_preparation()
   if (!_preparation.has_cached_elem_data)
     this->cache_elem_data();
 
+  // libMesh expects every processor to know about every subdomain
+  // name, but distributed mesh generators may only have set names for
+  // the part of the mesh they know about, so make sure the map is
+  // consistent everywhere.
+  if (!_preparation.has_synched_subdomain_name_map)
+    this->sync_subdomain_name_map();
+
   // Search the mesh for elements that have a neighboring element
   // of dim+1 and set that element as the interior parent
   if (!_preparation.has_interior_parent_ptrs)
@@ -1879,6 +1886,7 @@ bool MeshBase::get_count_lower_dim_elems_in_point_locator() const
 
 std::string & MeshBase::subdomain_name(subdomain_id_type id)
 {
+  this->unset_has_synched_subdomain_name_map();
   return _block_id_to_name[id];
 }
 
@@ -2043,6 +2051,8 @@ void MeshBase::sync_subdomain_name_map()
   parallel_object_only();
 
   this->comm().set_union(_block_id_to_name);
+
+  _preparation.has_synched_subdomain_name_map = true;
 }
 
 
@@ -2809,7 +2819,8 @@ MeshBase::Preparation::Preparation() :
   has_removed_remote_elements(false),
   has_removed_orphaned_nodes(false),
   has_boundary_id_sets(false),
-  has_reinit_ghosting_functors(false)
+  has_reinit_ghosting_functors(false),
+  has_synched_subdomain_name_map(false)
 {}
 
 MeshBase::Preparation::operator bool() const
@@ -2822,7 +2833,8 @@ MeshBase::Preparation::operator bool() const
          has_removed_remote_elements &&
          has_removed_orphaned_nodes &&
          has_reinit_ghosting_functors &&
-         has_boundary_id_sets;
+         has_boundary_id_sets &&
+         has_synched_subdomain_name_map;
 }
 
 MeshBase::Preparation &
@@ -2837,6 +2849,7 @@ MeshBase::Preparation::operator= (bool set_all)
   has_removed_orphaned_nodes = set_all;
   has_reinit_ghosting_functors = set_all;
   has_boundary_id_sets = set_all;
+  has_synched_subdomain_name_map = set_all;
 
   return *this;
 }
@@ -2862,6 +2875,8 @@ MeshBase::Preparation::operator== (const Preparation & other) const
     return false;
   if (has_boundary_id_sets != other.has_boundary_id_sets)
     return false;
+  if (has_synched_subdomain_name_map != other.has_synched_subdomain_name_map)
+    return false;
 
   return true;
 }

src/mesh/replicated_mesh.C

@@ -112,15 +112,15 @@ ReplicatedMesh::ReplicatedMesh (const MeshBase & other_mesh) :
 
   this->copy_constraint_rows(other_mesh);
 
-  this->_preparation = other_mesh.preparation();
-
   auto & this_boundary_info = this->get_boundary_info();
   const auto & other_boundary_info = other_mesh.get_boundary_info();
 
   this_boundary_info = other_boundary_info;
 
   this->set_subdomain_name_map() = other_mesh.get_subdomain_name_map();
 
+  this->_preparation = other_mesh.preparation();
+
   // If other_mesh is distributed, then we've got parts of it on each
   // processor but we're not replicated yet; fix that.
   if (!other_mesh.is_serial())