Feature: Add element and user data to mesh handle #2005

lenaploetzke · 2025-11-28T12:33:40Z

Closes #2006

Describe your changes here:
The mesh handle class is now able to handle element and user data. Template parameters are used to specify the classes (instead of the void* used in the forest for the user data). To specify them as template parameters, i needed to somehow pack the Competences into one template parameter (see parameter_pack.hxx) (because i wanted defaults for the element and user data classes but a parameter pack also always has to be the last template parameter). I think its a feature to have them all in one template parameter for the user and makes it easier to use (although slightly more complicated as a developer). Additionally, i can now provide predefined parameter packs e.g. cache_competences, where all cache competences are included.
The element data is stored in a vector in the mesh (and not in the elements). This is easier for the ghost exchange.
Additionally, the volume of the elements can now be accessed and cached. A tutorial used this as element data which is why i got inspired and also implemented the functionality for the handle. The calculation can be somehow complicated which is why i also provide a cached version.

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codecov · 2025-11-28T13:08:41Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.48%. Comparing base (4910843) to head (0c611eb).

Additional details and impacted files

@@                      Coverage Diff                      @@
##           handle-neighbor-and-ghost    #2005      +/-   ##
=============================================================
+ Coverage                      77.42%   77.48%   +0.05%     
=============================================================
  Files                            112      112              
  Lines                          19037    19086      +49     
=============================================================
+ Hits                           14739    14788      +49     
  Misses                          4298     4298

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…e mesh

sandro-elsweijer · 2026-01-13T12:13:55Z

mesh_handle/element.hxx

+   * Element data for non-ghost elements can be accessed (if set) directly.
+   * \return Element data with data of Type mesh_class::ElementDataType.
+   */
+  template <typename E = typename mesh_class::ElementDataType, typename = std::enable_if_t<!std::is_void<E>::value>>


Please use proper template parameter names

sandro-elsweijer · 2026-01-13T12:22:07Z

mesh_handle/element.hxx

+   * \note You can only set element data for non-ghost elements.
+   * \param [in] element_data The element data to be set.
+   */
+  template <typename E = typename mesh_class::ElementDataType, typename = std::enable_if_t<!std::is_void<E>::value>>


Parameter name

sandro-elsweijer · 2026-01-13T12:23:56Z

mesh_handle/element.hxx

+    // Resize for the case that no data vector has been set previously.
+    m_mesh->m_element_data.resize (m_mesh->get_num_local_elements () + m_mesh->get_num_ghosts ());
+    m_mesh->m_element_data[get_element_handle_id ()] = element_data;
+  }


IMHO we could also overload the dereference operator. In my head it makes total sense that an element handle stores data and that you can access its data by dereferencing it.

Ah but then we cannot check if the user tries to set data for a ghost element

sandro-elsweijer · 2026-01-13T12:24:56Z

mesh_handle/element.hxx

+  const E&
+  get_element_data () const
+  {
+    return m_mesh->m_element_data[get_element_handle_id ()];
+  }


Do we need a check if the element has data in the first place?

sandro-elsweijer · 2026-01-13T12:37:32Z

mesh_handle/element.hxx

+    SC_CHECK_ABORT (!m_is_ghost_element, "Element data cannot be set for ghost elements.\n");
+    // Resize for the case that no data vector has been set previously.
+    m_mesh->m_element_data.resize (m_mesh->get_num_local_elements () + m_mesh->get_num_ghosts ());
+    m_mesh->m_element_data[get_element_handle_id ()] = element_data;


Suggested change

m_mesh->m_element_data[get_element_handle_id ()] = element_data;

m_mesh->m_element_data[get_element_handle_id ()] = std::move(element_data);

sandro-elsweijer · 2026-01-13T13:44:40Z

test/mesh_handle/t8_gtest_handle_data.cxx

+  t8_forest_t forest = t8_forest_new_uniform (cmesh, init_scheme, level, 1, sc_MPI_COMM_WORLD);
+
+  using mesh_class = t8_mesh_handle::mesh<t8_mesh_handle::competence_pack<>, void, data_per_element>;
+  mesh_class mesh = mesh_class (forest);


Suggested change

mesh_class mesh = mesh_class (forest);

mesh_class mesh (forest);

sandro-elsweijer · 2026-01-13T13:46:51Z

test/mesh_handle/t8_gtest_mesh_handle.cxx

-  using element_class = mesh_class::element_class;
-  mesh_class mesh = mesh_class (forest);
+  using element_class = typename mesh_class::element_class;
+  const mesh_class mesh = mesh_class (forest);


Suggested change

const mesh_class mesh = mesh_class (forest);

const mesh_class mesh (forest);

sandro-elsweijer · 2026-01-13T13:47:08Z

test/mesh_handle/t8_gtest_mesh_handle.cxx

+  using competence_vertex_coordinates = t8_mesh_handle::competence_pack<t8_mesh_handle::cache_vertex_coordinates>;
+  using mesh_class_vertex = t8_mesh_handle::mesh<competence_vertex_coordinates>;
+  using element_class_vertex = typename mesh_class_vertex::element_class;
+  const mesh_class_vertex mesh_vertex = mesh_class_vertex (forest);


Suggested change

const mesh_class_vertex mesh_vertex = mesh_class_vertex (forest);

const mesh_class_vertex mesh_vertex (forest);

sandro-elsweijer · 2026-01-13T13:48:03Z

test/mesh_handle/t8_gtest_mesh_handle.cxx

+  using competence_centroid = t8_mesh_handle::competence_pack<t8_mesh_handle::cache_centroid>;
+  using mesh_class_centroid = t8_mesh_handle::mesh<competence_centroid>;
+  using element_class_centroid = typename mesh_class_centroid::element_class;
+  const mesh_class_centroid mesh_centroid = mesh_class_centroid (forest);


Suggested change

const mesh_class_centroid mesh_centroid = mesh_class_centroid (forest);

const mesh_class_centroid mesh_centroid (forest);

sandro-elsweijer · 2026-01-13T13:48:15Z

test/mesh_handle/t8_gtest_mesh_handle.cxx

-  mesh_class mesh = mesh_class (forest);
+  using mesh_class = t8_mesh_handle::mesh<t8_mesh_handle::cache_competences>;
+  using element_class = typename mesh_class::element_class;
+  const mesh_class mesh = mesh_class (forest);


Suggested change

const mesh_class mesh = mesh_class (forest);

const mesh_class mesh (forest);

lenaploetzke added 11 commits November 10, 2025 11:11

pack competences into one class

e5051fd

rm assert committed in the test

1701534

Not working: implement user data

27fcc41

fix error

df0353c

Merge branch 'handle-neighbor-and-ghost' into handle_element-data

9b272a9

added test

b3dc96e

implement get_volume with cache

58559f3

add check for ghost test that we actually test smth

8d94a95

add element data functionality

e7934cc

rename test

a1cabed

adapt cmake

5119d03

spenke91 assigned sandro-elsweijer Dec 1, 2025

spenke91 requested a review from sandro-elsweijer December 1, 2025 14:59

lenaploetzke added 7 commits December 17, 2025 09:12

Merge branch 'main' into handle_element-data

7c57b3e

Merge branch 'handle-neighbor-and-ghost' into handle_element-data

08f6e26

Merge branch 'handle-neighbor-and-ghost' into handle_element-data

98a96da

resolve doxygen warnings

c2a78f5

Merge branch 'handle-neighbor-and-ghost' into handle_element-data

16c9687

provide option to set element data via element instead of only via th…

277dc06

…e mesh

typo

b493c5f

lenaploetzke assigned lenaploetzke and unassigned sandro-elsweijer Jan 7, 2026

lenaploetzke added 4 commits January 8, 2026 09:35

doxygen

7d79e3f

Merge branch 'handle-neighbor-and-ghost' into handle_element-data

efc900e

easier competence checks

e8b023a

Merge branch 'handle-neighbor-and-ghost' into handle_element-data

dc1fd8b

lenaploetzke assigned sandro-elsweijer and unassigned lenaploetzke Jan 8, 2026

sandro-elsweijer requested changes Jan 13, 2026

View reviewed changes

sandro-elsweijer assigned lenaploetzke and unassigned sandro-elsweijer Jan 13, 2026

Merge branch 'handle-neighbor-and-ghost' into handle_element-data

0c611eb

	m_mesh->m_element_data[get_element_handle_id ()] = element_data;
	m_mesh->m_element_data[get_element_handle_id ()] = std::move(element_data);

	mesh_class mesh = mesh_class (forest);
	mesh_class mesh (forest);

	const mesh_class mesh = mesh_class (forest);
	const mesh_class mesh (forest);

	const mesh_class_vertex mesh_vertex = mesh_class_vertex (forest);
	const mesh_class_vertex mesh_vertex (forest);

	const mesh_class_centroid mesh_centroid = mesh_class_centroid (forest);
	const mesh_class_centroid mesh_centroid (forest);

Feature: Add element and user data to mesh handle #2005

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lenaploetzke commented Nov 28, 2025 •

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