Change NumericVector::upgrade_to_ghosted() -> NumericVector::set_type()

Making this a generic setter opens up the possibility that we will
support more complicated/expensive type conversions later. For now, we
just throw a libmesh_not_implemented() error when the user requests to
change the ParallelType of an already-initialized NumericVector.

Author: jwpeterson

include/numerics/numeric_vector.h

@@ -154,12 +154,15 @@ class NumericVector : public ReferenceCountedObject<NumericVector<T>>,
   ParallelType type() const { return _type; }
 
   /**
-   * If this vector's type() is PARALLEL and it is not yet
-   * initialized, change the type() to GHOSTED.
-   *
-   * \returns \p true if the upgrade was performed, false otherwise.
-   */
-  bool upgrade_to_ghosted();
+   * Allow the user to change the ParallelType of the NumericVector
+   * under some circumstances. If the NumericVector has not been
+   * initialized yet, then it is generally safe to change the
+   * ParallelType. otherwise, if the NumericVector has already been
+   * initialized with a specific type, we cannot change it without
+   * doing some extra copying/reinitialization work, and we currently
+   * throw an error if this is requested.
+   */
+  void set_type(ParallelType t);
 
   /**
    * \returns \p true if the vector is closed and ready for

src/numerics/numeric_vector.C

@@ -83,24 +83,34 @@ NumericVector<T>::build(const Parallel::Communicator & comm,
 
 
 template <typename T>
-bool NumericVector<T>::upgrade_to_ghosted()
+void NumericVector<T>::set_type(ParallelType t)
 {
-  // Can't upgrade to GHOSTED if libMesh was configured with --disable-ghosted
+  // Check for no-op
+  if (_type == t)
+    return;
+
+  // If the NumericVector is not yet initialized, then it is generally
+  // safe to change the ParallelType, with minor restrictions.
+  if (!this->initialized())
+    {
+      // If ghosted vectors are not enabled and the user requested a
+      // GHOSTED vector, fall back on SERIAL.
 #ifndef LIBMESH_ENABLE_GHOSTED
-  return false;
+      if (t == GHOSTED)
+        {
+          _type = SERIAL;
+          return;
+        }
 #endif
 
-  // We can only upgrade NumericVectors that are currently PARALLEL type
-  // and not yet initialized.
-  if (this->type() == PARALLEL && !this->initialized())
-  {
-    _type = GHOSTED;
-    return true;
-  }
+      _type = t;
+      return;
+    }
 
-  // If we made it here, then the upgrade to GHOSTED could not be
-  // performed for some reason, so return false.
-  return false;
+  // If we made it here, then the NumericVector was already
+  // initialized and we don't currently allow the ParallelType to be
+  // changed, although this could potentially be added later.
+  libmesh_not_implemented();
 }
 
 template <typename T>

src/systems/system.C

@@ -792,8 +792,9 @@ NumericVector<Number> & System::add_vector (std::string_view vec_name,
                   vec.swap(*new_vec);
                 }
               else
-                // The PARALLEL vec is not yet initialized, so we can just "upgrade" it to GHOSTED
-                vec.upgrade_to_ghosted();
+                // The PARALLEL vec is not yet initialized, so we can
+                // just "upgrade" it to GHOSTED.
+                vec.set_type(type);
             }
         }