Skip some operations in interior parents computation

include/mesh/mesh_base.h

@@ -206,8 +206,7 @@ class MeshBase : public ParallelObject
    * the preparation done in a call to \p prepare_for_use, \p false
    * otherwise.
    */
-  bool is_prepared () const
-  { return _preparation; }
+  bool is_prepared () const;
 
   /**
    * \returns the \p Preparation structure with details about in what
@@ -1358,6 +1357,13 @@ class MeshBase : public ParallelObject
   void allow_find_neighbors(bool allow) { _skip_find_neighbors = !allow; }
   bool allow_find_neighbors() const { return !_skip_find_neighbors; }
 
+  /**
+   * If \p false is passed then this mesh will no longer work to detect
+   * interior parents when being prepared for use
+   */
+  void allow_detect_interior_parents(bool allow) { _skip_detect_interior_parents = !allow; }
+  bool allow_detect_interior_parents() const { return !_skip_detect_interior_parents; }
+
   /**
    * If false is passed in then this mesh will no longer have remote
    * elements deleted when being prepared for use; i.e. even a
@@ -1555,7 +1561,8 @@ class MeshBase : public ParallelObject
   virtual void read  (const std::string & name,
                       void * mesh_data=nullptr,
                       bool skip_renumber_nodes_and_elements=false,
-                      bool skip_find_neighbors=false) = 0;
+                      bool skip_find_neighbors=false,
+                      bool skip_detect_interior_parents=false) = 0;
   virtual void write (const std::string & name) const = 0;
 
   /**
@@ -2014,53 +2021,37 @@ class MeshBase : public ParallelObject
    */
   struct Preparation
   {
-    bool is_partitioned = false,
-         has_synched_id_counts = false,
-         has_neighbor_ptrs = false,
-         has_cached_elem_data = false,
-         has_interior_parent_ptrs = false,
-         has_removed_remote_elements = false,
-         has_removed_orphaned_nodes = false,
-         has_boundary_id_sets = false,
-         has_reinit_ghosting_functors = false;
-
-    operator bool() const {
-      return is_partitioned &&
-             has_synched_id_counts &&
-             has_neighbor_ptrs &&
-             has_cached_elem_data &&
-             has_interior_parent_ptrs &&
-             has_removed_remote_elements &&
-             has_removed_orphaned_nodes &&
-             has_reinit_ghosting_functors &&
-             has_boundary_id_sets;
-    }
-
-    Preparation & operator= (bool set_all) {
-      is_partitioned = set_all;
-      has_synched_id_counts = set_all;
-      has_neighbor_ptrs = set_all;
-      has_cached_elem_data = set_all;
-      has_interior_parent_ptrs = set_all;
-      has_removed_remote_elements = set_all;
-      has_removed_orphaned_nodes = set_all;
-      has_reinit_ghosting_functors = set_all;
-      has_boundary_id_sets = set_all;
-
-      return *this;
-    }
-
-    bool operator== (const Preparation & other) {
-      return is_partitioned == other.is_partitioned &&
-             has_synched_id_counts == other.has_synched_id_counts &&
-             has_neighbor_ptrs == other.has_neighbor_ptrs &&
-             has_cached_elem_data == other.has_cached_elem_data &&
-             has_interior_parent_ptrs == other.has_interior_parent_ptrs &&
-             has_removed_remote_elements == other.has_removed_remote_elements &&
-             has_removed_orphaned_nodes == other.has_removed_orphaned_nodes &&
-             has_reinit_ghosting_functors == other.has_reinit_ghosting_functors &&
-             has_boundary_id_sets == other.has_boundary_id_sets;
-    }
+    /**
+     * Constructor. Initializes all flags to false.
+     */
+    Preparation();
+
+    /**
+     * Returns true iff all the flags are true.
+     */
+    explicit operator bool() const;
+
+    /**
+     * Set all flags to the "set_all" value.
+     */
+    Preparation & operator= (bool set_all);
+
+    /**
+     * Two Preparation objects are equivalent iff all the flags match,
+     * regardless of the true/false status of any given flag.
+     */
+    bool operator== (const Preparation & other) const;
+    bool operator!= (const Preparation & other) const;
+
+    bool is_partitioned;
+    bool has_synched_id_counts;
+    bool has_neighbor_ptrs;
+    bool has_cached_elem_data;
+    bool has_interior_parent_ptrs;
+    bool has_removed_remote_elements;
+    bool has_removed_orphaned_nodes;
+    bool has_boundary_id_sets;
+    bool has_reinit_ghosting_functors;
   };
 
 protected:
@@ -2204,6 +2195,11 @@ class MeshBase : public ParallelObject
    */
   bool _skip_find_neighbors;
 
+  /**
+   * If this is \p true then we will skip \p detect_interior_parents in \p prepare_for_use
+   */
+  bool _skip_detect_interior_parents;
+
   /**
    * If this is false then even on DistributedMesh remote elements
    * will not be deleted during mesh preparation.

include/mesh/unstructured_mesh.h

@@ -109,7 +109,8 @@ class UnstructuredMesh : public MeshBase
   virtual void read (const std::string & name,
                      void * mesh_data=nullptr,
                      bool skip_renumber_nodes_and_elements=false,
-                     bool skip_find_neighbors=false) override;
+                     bool skip_find_neighbors=false,
+                     bool skip_detect_interior_parents=false) override;
   /**
    * Write the file specified by \p name.  Attempts to figure out the
    * proper method by the file extension.

src/mesh/distributed_mesh.C

@@ -195,6 +195,7 @@ DistributedMesh::DistributedMesh (const MeshBase & other_mesh) :
   this->copy_nodes_and_elements(other_mesh, true, 0, 0, 0, nullptr, true);
 
   this->allow_find_neighbors(other_mesh.allow_find_neighbors());
+  this->allow_detect_interior_parents(other_mesh.allow_detect_interior_parents());
   this->allow_renumbering(other_mesh.allow_renumbering());
   this->allow_remote_element_removal(other_mesh.allow_remote_element_removal());
   this->skip_partitioning(other_mesh.skip_partitioning());