Minimum length of element

dolfinx
1

Hello all,

Here is MWE for calculating the minimum element length, which works smoothly on 0.8.0, but on the latest docker nightly installation of dolfinx 0.9.0.0, it results an error.

# Scaled variable
import dolfinx
from mpi4py import MPI
from dolfinx import mesh, fem, plot, io, default_scalar_type
from petsc4py import PETSc
import numpy as np

def mpi_print(s):
    print(f"Rank {comm.rank}: {s}")

dtype = PETSc.ScalarType  # type: ignore
comm = MPI.COMM_WORLD
rank = comm.rank

# prints dolfinx version
mpi_print(f"DOLFINx version: {dolfinx.__version__}")

domain = mesh.create_box(MPI.COMM_WORLD, [[0.0, 0.0, 0.0], [1, 1, 1]], [3, 2, 1], mesh.CellType.hexahedron)
# Assuming `mesh` is the mesh created in the code
num_elements = domain.topology.index_map(3).size_local
num_nodes = domain.topology.index_map(0).size_local
# Summing up the counts from all processes in MPI_COMM_WORLD
num_elements_global = MPI.COMM_WORLD.allreduce(num_elements, op=MPI.SUM)
num_nodes_global = MPI.COMM_WORLD.allreduce(num_nodes, op=MPI.SUM)

mpi_print(f"Number of elements: {num_elements_global}")
mpi_print(f"Number of nodes: {num_nodes_global}")

# filter and projection parameters
tdim = domain.topology.dim
num_cells = domain.topology.index_map(tdim).size_local + domain.topology.index_map(tdim).num_ghosts
h = domain.h(tdim-2, np.arange(num_cells))
hmax = max(h)
hmin = min(h)
mpi_print(f"Max Element Size: {hmax}")
mpi_print(f"Min Element Size: {hmin}")

Output on Dolfinx 0.8.0

Rank 0: DOLFINx version: 0.8.0
Rank 0: Number of elements: 6
Rank 0: Number of nodes: 24
Rank 0: Max Element Size: 1.0
Rank 0: Min Element Size: 0.3333333333333333

Output on docker nightly Dolfinx 0.9.0.0

Rank 0: DOLFINx version: 0.9.0.0
Rank 0: Number of elements: 6
Rank 0: Number of nodes: 24
Traceback (most recent call last):
  File "/home/versiontest/vertest2.py", line 32, in <module>
    h = domain.h(tdim-2, np.arange(num_cells))
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/dolfinx-real/lib/python3.12/dist-packages/dolfinx/mesh.py", line 346, in h
    return _cpp.mesh.h(self._cpp_object, dim, entities)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: Entity-to-cell connectivity has not been computed. Missing dims 1->3

Can anyone please let me know the changes I require on the latest version?

Thanks.

1 Like
2

I’m not sure what happened with the interface between these versions. Try replacing

h = domain.h(tdim-2, np.arange(num_cells))

with a direct use of the C++ function

import dolfinx
domain.topology.create_connectivity(tdim - 2, tdim)
h = dolfinx.cpp.mesh.h(domain._cpp_object, tdim-2, np.arange(num_cells))
3

It works with the C++ function.
Thank you @nate for quick response.

4

Simply add domain.topology.create_connectivity(tdim-2, tdim)
Prior to calling domain.h.
What has happened between versions is that dolfinx.mesh.entities_to_geometry was rewritten to support higher order mesh geometries, meaning that if you have a higher order geometry, these nodes are taken into account when computing h dolfinx/cpp/dolfinx/mesh/utils.h at main · FEniCS/dolfinx · GitHub

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