Add get_laplacians to MeshWorker::ScratchData

diff --git a/doc/news/changes/minor/20211012Jean-PaulPelteret-2 b/doc/news/changes/minor/20211012Jean-PaulPelteret-2
new file mode 100644 (file)
index 0000000..444796d
--- /dev/null
+++ b/doc/news/changes/minor/20211012Jean-PaulPelteret-2
@@ -0,0 +1,5 @@
+New: The MeshWorker::ScratchData class is now able to compute the Laplacians
+of the scalar-valued and vector-valued components of the solution vector.
+<br>
+(Jean-Paul Pelteret, 2021/03/13)
+

diff --git a/include/deal.II/meshworker/scratch_data.h b/include/deal.II/meshworker/scratch_data.h
index 2d7b3b5255274beca6e732a746cf3b39fe829078..13af08e5f8bd7d2211327608b06afe46416f60d0 100644 (file)
--- a/include/deal.II/meshworker/scratch_data.h
+++ b/include/deal.II/meshworker/scratch_data.h
@@ -751,6 +751,35 @@ namespace MeshWorker
                  const Extractor &  variable,
                  const Number       dummy = Number(0));
 
+    /**
+     * For the solution vector identified by @p global_vector_name, compute
+     * the Laplacians of the function at the quadrature points, and return a
+     * vector with the correct type deduced by the Extractor you passed as the
+     * @p variable argument.
+     *
+     * Before you can call this method, you need to call the
+     * extract_local_dof_values() method at least once, passing the same
+     * @p global_vector_name string, and the same type for the variable @p dummy.
+     *
+     * If you have not previously called the extract_local_dof_values() method,
+     * this function will throw an exception.
+     *
+     * For this function to work properly, the underlying FEValues,
+     * FEFaceValues, or FESubfaceValues object for which you called one of the
+     * reinit() functions, must have computed the information you are
+     * requesting. To do so, the update_hessians flag must be an element of the
+     * list of UpdateFlags that you passed to the constructor of this object.
+     * See "The interplay of UpdateFlags, Mapping, and FiniteElement" in
+     * the documentation of the FEValues class for more information.
+     */
+    template <typename Extractor, typename Number = double>
+    const std::vector<
+      typename internal::OutputType<dim, spacedim, Number, Extractor>::
+        laplacian_type> &
+    get_laplacians(const std::string &global_vector_name,
+                   const Extractor &  variable,
+                   const Number       dummy = Number(0));
+
     /**
      * For the solution vector identified by @p global_vector_name, compute
      * the third_derivatives of the function at the quadrature points, and
@@ -1130,6 +1159,45 @@ namespace MeshWorker
 
 
 
+  template <int dim, int spacedim>
+  template <typename Extractor, typename Number>
+  const std::vector<
+    typename internal::OutputType<dim, spacedim, Number, Extractor>::
+      laplacian_type> &
+  ScratchData<dim, spacedim>::get_laplacians(
+    const std::string &global_vector_name,
+    const Extractor &  variable,
+    const Number       dummy)
+  {
+    const std::vector<Number> &independent_local_dofs =
+      get_local_dof_values(global_vector_name, dummy);
+
+    const FEValuesBase<dim, spacedim> &fev = get_current_fe_values();
+
+    const unsigned int n_q_points = fev.n_quadrature_points;
+
+    const std::string name = get_unique_name(
+      global_vector_name, variable, "_laplacians_q", n_q_points, dummy);
+
+    // Now build the return type
+    using RetType = std::vector<
+      typename internal::OutputType<dim, spacedim, Number, Extractor>::
+        laplacian_type>;
+
+    RetType &ret =
+      internal_data_storage.template get_or_add_object_with_name<RetType>(
+        name, n_q_points);
+
+
+    AssertDimension(ret.size(), n_q_points);
+
+    fev[variable].get_function_laplacians_from_local_dof_values(
+      independent_local_dofs, ret);
+    return ret;
+  }
+
+
+
   template <int dim, int spacedim>
   template <typename Extractor, typename Number>
   const std::vector<