Improvement: Step 2 tutorial and get_num_global_elements to mesh.hxx by Vyp3er · Pull Request #2371 · DLR-AMR/t8code

Vyp3er · 2026-07-20T13:48:19Z

…mesh.hxx.

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…mesh.hxx.

codecov · 2026-07-20T14:19:04Z

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✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.28%. Comparing base (66cd94f) to head (54f48b6).

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lenaploetzke

Thanks for your nice work :)

lenaploetzke · 2026-07-27T05:50:03Z

+  /**
+   * Getter for the number of global elements in the mesh.
+   * \return Number of global elements in the mesh.
+   */
+  t8_gloidx_t
+  get_num_global_elements () const
+  {
+    return t8_forest_get_global_num_leaf_elements (m_forest);
+  }
+


Could you test this function somewhere? :)
As we discussed, please open separate PRs for each feature in the future.

lenaploetzke · 2026-07-27T05:50:50Z

+  t8code is a C library to manage a collection (a forest) of multiple
+  connected adaptive space-trees of general element types in parallel.
+
+  Copyright (C) 2015 the developers


Please always adapt the year if you are creating a new file!

lenaploetzke · 2026-07-27T05:52:16Z

+
+/** \file t8_mesh_step2_uniform_mesh.cxx
+ * This is step 2 of the t8code mesh handle tutorials.
+ * Therefor, this is the same as general/t8_step2_uniform_forest.cxx but using the mesh handle interface instead of the forest


Suggested change

* Therefor, this is the same as general/t8_step2_uniform_forest.cxx but using the mesh handle interface instead of the forest

* Therefore, this is the same as general/t8_step2_uniform_forest.cxx but using the mesh handle interface instead of the forest

lenaploetzke · 2026-07-27T05:55:07Z

+ * uniform (every element has the same refinement level) and can then be adapted
+ * later (see the following steps).
+ * Together with the cmesh, we also need a refinement scheme. This scheme tells the
+ * mesh how elements of each shape (t8_eclass_t) are refined, what their neighbor


Suggested change

* mesh how elements of each shape (t8_eclass_t) are refined, what their neighbor

* mesh how elements of each shape (t8_eclass_t) are refined, what their neighbors

lenaploetzke · 2026-07-27T05:57:35Z

+ * mesh how elements of each shape (t8_eclass_t) are refined, what their neighbor
+ * are etc.
+ * The default scheme in t8_schemes/t8_default/t8_default.hxx provides an implementation for
+ * all element shapes that t8code supports (with pyramids currently under construction).


Suggested change

* all element shapes that t8code supports (with pyramids currently under construction).

* all element shapes that t8code supports.

Where did you copy this from? Could you maybe also adapt it also there? :) The scheme for pyramids is usable :)

lenaploetzke · 2026-07-27T07:21:57Z

+  t8_global_productionf (" [tutorial] Wrote mesh to vtu files:\t%s*\n", prefix);
+
+  /** Destroy the mesh. */
+  mesh.reset ();


Yes, this destroys the mesh but by resetting the unique pointer to nullptr.
I prefer the {} lifetime declaration as in the other tutorials because we have no leftover pointer :)

(The cool part about the mesh is that you do not need to destroy the mesh mannually), only need the {} for the lifetime, please also explain this in a comment

lenaploetzke · 2026-07-27T07:26:01Z

+ * \return            A uniform mesh with the given refinement level that is
+ *                    partitioned across the processes in \a comm.
+ */
+static std::unique_ptr<t8_mesh_handle::mesh<t8_mesh_handle::all_cache_element_competences>>


I am not sure if its maybe better to write a templated function here.

lenaploetzke · 2026-07-27T07:27:38Z

+
+  /* Build the uniform mesh, it is automatically partitioned among the processes. */
+  auto mesh = t8_mesh_handle::handle_new_uniform<t8_mesh_handle::mesh<t8_mesh_handle::all_cache_element_competences>> (
+    cmesh, scheme, level, comm, false);


As the last parameter is optional, and we want to write a tutorial that is as easy as possible, i would leave out the false here.

lenaploetzke · 2026-07-27T07:30:10Z

+  const t8_scheme *scheme = t8_scheme_new_default (); /** Default refinement scheme. */
+
+  /* Build the uniform mesh, it is automatically partitioned among the processes. */
+  auto mesh = t8_mesh_handle::handle_new_uniform<t8_mesh_handle::mesh<t8_mesh_handle::all_cache_element_competences>> (


Auto is in general fine here but could you state the full type here such that it is clear why we return a unique pointer?

lenaploetzke · 2026-07-27T07:31:03Z

+ * \return            A uniform mesh with the given refinement level that is
+ *                    partitioned across the processes in \a comm.
+ */
+static std::unique_ptr<t8_mesh_handle::mesh<t8_mesh_handle::all_cache_element_competences>>


unique_ptr is declared in header, could you include it?

Added tutorial Step 2 and getter function get_num_global_elements to …

54f48b6

…mesh.hxx.

Vyp3er marked this pull request as ready for review July 20, 2026 14:02

lenaploetzke self-assigned this Jul 21, 2026

lenaploetzke self-requested a review July 21, 2026 07:55

lenaploetzke requested changes Jul 27, 2026

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lenaploetzke assigned Vyp3er and unassigned lenaploetzke Jul 27, 2026

	* Therefor, this is the same as general/t8_step2_uniform_forest.cxx but using the mesh handle interface instead of the forest
	* Therefore, this is the same as general/t8_step2_uniform_forest.cxx but using the mesh handle interface instead of the forest

	* mesh how elements of each shape (t8_eclass_t) are refined, what their neighbor
	* mesh how elements of each shape (t8_eclass_t) are refined, what their neighbors

	* all element shapes that t8code supports (with pyramids currently under construction).
	* all element shapes that t8code supports.

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Vyp3er commented Jul 20, 2026 •

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