Value of a variable at each grid point

1

I would like to use the solution of one simulation to create the subdomains in a different simulation. Thus, I save the solution in a file like this:

vtkfile = File('output/solution.pvd')
vtkfile << (u, t)

Since the new simulation will have the same mesh, I also save the subdomains as follows:

mesh_file = File("output/subdomains.pvd")
mesh_file << subdomains

Then, I want to read the vtkfile and mesh_file files simultaneously and update the subdomains according to the results in vtkfile. However, I see that those files contain a different number of values: vtkfile has values for the NumberOfPoints and the mesh_file for the NumberOfCells, with NumberOfCells>>NumberOfPoints . How can I get the values for each NumberOfPoints ? What is the relation between both values?

2

Please create a minimal working code illustrating what you would like to achieve.
A mesh contains a number of nodes (usually vertices) and a number of cells (for instance triangles or tetrahedrons) which is a collection of vertices (three for triangles and four for tetrahedrons).

When saving a function from any function space as pvd, an interpolation into CG-1 is performed, thus you will have one value per vertex.