Meta data of dolfinx objects

metadata.md

Meta data of dolfinx objects

Mesh

Mesh data is constant over time.

1. Attributes

• name : name of the mesh
• dim : geometrical dimension of the mesh
• cell_type : cell type of the coordinate element
• degree :
• lagrange_variant : integration points

2. Variables

   • Scalars

     • num_vertices : number of vertices in the mesh
     • num_cells : number of cells
     • num_dofs_per_cell :

   • Arrays

     • x : coordinate array, size (num_vertices, 3)
     • topology : cell to vertex connectivity
       • topology_array : flattened array
       • topolgy_offset : offsets demarcating the cells
     • input_global_indices : original input mesh's global indices
     • orginal_cell_indices : original input mesh's cell indices

Meshtags

Note:

1. One can have meshtags for different entity types: points, edges, facets, cells.

2. One can have multiplicities of meshtags for the same entity type.

3. Suffixes, prefixes can be used.

4. Attributes

   • name

5. Variables

   • Scalars

     • num_tag_entities_global_{entity}
     • num_dofs_per_entity_{entity}
     • num_saved_tag_entities_{entity}

   • Arrays

     • topology_{entity}
     • values_{entity}

Function

Note:

1. Multiplicities of FunctionSpaces

2. Multiplicities of Functions from the same FunctionSpace

3. Attributes

   • functionspace_names :
   • function_names : Array of strings of function names

4. Variables

   • Scalars

     • num_cells_global
     • num_dofs_per_cell : different than the one for mesh
     • dofmap_bs :
     • num_dofs_global_dmap :

   • Arrays

     • cell_permutations :
     • topology :
       • topology_array : dofmap of the function space
       • topology_offsets : xdofmap
     • values :

ADIOS2 variables

One needs to define ADIOS2 variables for each of the above. Should we create the ADIOS2 variable with some prefix/suffix to the above variable names?

Example:

   adios2::Variable<T> values_var = io.DefineVariable<T>(funcname + "_values",
                                                {num_dofs_global},
                                                {dof_offset},
                                                {num_dofs_local},
                                                adios2::ConstantDims);
 
   writer.Put(values_var, values.data());

num_vertices is not necessarily correct for higher order meshes.
num_nodes would be a better name

I guess the num_dofs_per_cell-variable is not required if you store topolgy_offset as it would give the same information, but more generalized for multiple cell type topologies (if one store these in one array).

Could you elaborate on what:

    num_tag_entities_global_{entity}
    num_dofs_per_entity_{entity}
    num_saved_tag_entities_{entity}

signifies?
num_tag_entities_global should be possible to infer from the shape of values_{entity}?
Similarly, one can then infer num_dofs_per_entity_{entity} from the shape of topology_{entity} as ADIOS2 allows you to store two-dimensional arrays. Of course, if we want to target multiple cell type meshes, one would have to store this topology with an array and offsets, as done in the mesh.

For Function, same comment regarding num_dofs_per_cell, as this would be inferred from topology offsets, and would work for multi-cell meshes.