Feature: Add interpolate data functionality to mesh handle by lenaploetzke · Pull Request #2382 · DLR-AMR/t8code

lenaploetzke · 2026-07-29T14:35:54Z

Closes #2383
This also Closes #2115 as we dont need this functionality for the feature (expected before) and also PR #2248 is not needed anymore.
I think we can also
Closes #1654
as this completes the core functionality.

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codecov · 2026-08-06T10:34:14Z

Codecov Report

❌ Patch coverage is 94.50549% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.36%. Comparing base (f63e8b8) to head (a7bdf99).
⚠️ Report is 25 commits behind head on main.

Files with missing lines	Patch %	Lines
mesh_handle/internal/interpolate.hxx	91.17%	3 Missing ⚠️
mesh_handle/mesh.hxx	93.93%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2382      +/-   ##
==========================================
+ Coverage   82.28%   82.36%   +0.08%     
==========================================
  Files         125      126       +1     
  Lines       20701    20791      +90     
==========================================
+ Hits        17033    17125      +92     
+ Misses       3668     3666       -2

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spenke91

Well, that was a nice dive into modern C++ template magic! 🪄
Took some time to get it, but I think the code is quite well designed. Great work @lenaploetzke !

I only have a bunch of small remarks and questions. To avoid spamming, I mostly refrained from adding hyphen-related comments; instead I would suggest the following replacements

user defined -> user-defined
index based -> index-based
span based -> span-based
element data handling -> element-data handling

But enough of being picky! Great feature, thanks a lot! 🙂
``

spenke91 · 2026-08-18T11:30:56Z

 * This header file collects macros that are needed for
 * the forest and cmesh vtk routines.
- * \see t8_forest_vtk.h \see t8_cmesh_vtk_writer.h \see t8_cmesh_vtk_reader.hxx
+ * \see t8_forest_vtk.h \see t8_cmesh_vtk_writer.h \see t8_cmesh_vtk_reader.hxx TODO


spenke91 · 2026-08-18T11:31:40Z

    = std::function<int (const SelfType& mesh, std::span<const element_class> elements, TUserDataType user_data)>;

+  /** Callback function prototype to interpolate the element data after refining or coarsening.
+   * \note You need to include \ref interpolate_element_data_mesh_competence to you competences to be able to


Suggested change

* \note You need to include \ref interpolate_element_data_mesh_competence to you competences to be able to

* \note You need to include \ref interpolate_element_data_mesh_competence to your competences to be able to

spenke91 · 2026-08-31T12:19:48Z

- * Use both competences together if you want to manage element data for the elements of the mesh and access it directly for each element.
+ * The file defines mesh and element competences for element data handling.
+ * The mesh competences make it possible to manage element data and exchange it for ghost elements between processes. 
+ * The element competences makes it possible to access these element data directly for each element of the mesh.


Suggested change

* The element competences makes it possible to access these element data directly for each element of the mesh.

* The element competences makes it possible to access this element data directly for each element of the mesh.

spenke91 · 2026-08-31T12:20:09Z

+ * The file defines mesh and element competences for element data handling.
+ * The mesh competences make it possible to manage element data and exchange it for ghost elements between processes. 
+ * The element competences makes it possible to access these element data directly for each element of the mesh.
+ * A competence to interpolate data after adaptation using a user defined callback is provided.


Suggested change

* A competence to interpolate data after adaptation using a user defined callback is provided.

* Also, a competence to interpolate data after adaptation using a user-defined callback is provided.

spenke91 · 2026-08-31T12:47:10Z

+
+  /** Templated callback function prototype to interpolate the element data after refining or coarsening, 
+   * including user data.
+   * See the version without user_data \ref interpolate_callback_type for more details!


Suggested change

* See the version without user_data \ref interpolate_callback_type for more details!

* See the version without user_data \ref interpolate_callback_type for more details.

🙂

spenke91 · 2026-09-01T08:54:59Z

+   * \param [in] forest_to   The committed forest that was partitioned from \a forest_from.
+   * \note Both forests could also be accessed directly (by this->underlying()) but this requires that the function is
+   * called on the exact right states of m_forest and m_uncommitted_forest. 
+   * Providing the variables is the saver implementation.


Suggested change

* Providing the variables is the saver implementation.

* Providing the variables is the safer implementation.

spenke91 · 2026-09-01T09:24:38Z

+            SelfType new_mesh (m_uncommitted_forest.value ());
+            t8_forest_ref (m_uncommitted_forest.value ());
+            // Register the interpolate context with the callback for the new mesh. With this, the standard
+            // iterate replace can be called.


Suggested change

// iterate replace can be called.

// iterate replace can be called, passing the mesh's callback.

spenke91 · 2026-09-01T09:29:04Z

+            t8_global_infof ("No interpolation context set.\n");
+          }
+        }
+        else {
+          t8_global_infof ("The element data was not interpolated during adaptation. Use set_element_data() to provide "
+                           "new data or use the mesh competence interpolate_element_data_mesh_competence.\n");


Should this even be errors?

spenke91 · 2026-09-01T09:30:19Z

+  /** Function that checks if a competence for the interpolation of element data is given.
+   * \return true if mesh has the competence, false otherwise.
+   */
+  static constexpr bool
+  has_interpolate_data_competence ()
+  {
+    return requires (SelfType& mesh) { mesh.set_partition_called (); };
+  }
+


Is this really a clean way of checking it has the competence? Seems strange and weird to maintain to me 🤔

spenke91 · 2026-09-01T09:33:56Z

+  static std::unordered_map<t8_forest_t, std::unique_ptr<mesh_interpolate_context_base>>&
+  get_map ()
+  {
+    static std::unordered_map<t8_forest_t, std::unique_ptr<mesh_interpolate_context_base>> map;


The whole std::unorder_map construct seems a little over-engineered to me. Out of curiosity: Do we already know whether we might ever register more than one forest-context pair at a time? If not, maybe we could make this whole registry more lightweight. On the other hand, I also don't mind having it a little too generic and flexible...

lenaploetzke added 20 commits March 27, 2026 15:30

functionality for new element data

b83ef5a

[run ci] doxygen

734affa

add file

08434d3

first ideas

a50f0a4

gitignore remove

a0de5f8

ideas for interpolate

2c3585f

use gtest common

0377490

no errors, very first version of test

6211e6b

interpolate

9668d8d

working version

236175d

remove new element data

4533f7d

Merge branch 'new-handle-mesh-competences' into handle-interpolate-data

dd6cf43

status

4c0b66d

Merge branch 'main' into handle-interpolate-data

afd64d2

fix things from merge

56de23b

renaming

ca55272

documentation

058f919

Add user data option for interpolate callback

d5d7848

Add repartition of data

b2c576d

resolve doxygen errors

4415d6a

lenaploetzke marked this pull request as draft August 3, 2026 06:17

Adapted test to be valid for each process number

e56d6ef

lenaploetzke marked this pull request as ready for review August 6, 2026 10:17

resolve doxygen error

a7bdf99

spenke91 self-assigned this Aug 10, 2026

spenke91 self-requested a review August 10, 2026 13:31

spenke91 requested changes Sep 1, 2026

View reviewed changes

spenke91 assigned lenaploetzke and unassigned spenke91 Sep 1, 2026

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Feature: Add interpolate data functionality to mesh handle - #2382

Feature: Add interpolate data functionality to mesh handle#2382
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lenaploetzke commented Jul 29, 2026 •

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	* \note You need to include \ref interpolate_element_data_mesh_competence to you competences to be able to
	* \note You need to include \ref interpolate_element_data_mesh_competence to your competences to be able to

	* The element competences makes it possible to access these element data directly for each element of the mesh.
	* The element competences makes it possible to access this element data directly for each element of the mesh.

	* A competence to interpolate data after adaptation using a user defined callback is provided.
	* Also, a competence to interpolate data after adaptation using a user-defined callback is provided.

	* See the version without user_data \ref interpolate_callback_type for more details!
	* See the version without user_data \ref interpolate_callback_type for more details.

	* Providing the variables is the saver implementation.
	* Providing the variables is the safer implementation.

	// iterate replace can be called.
	// iterate replace can be called, passing the mesh's callback.

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lenaploetzke commented Jul 29, 2026 •

edited by spenke91

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