Vector quadrature_element in FEniCSx 0.7.0

General
1

I am porting some (originally legacy) c++ code from fenicsx 0.6.0 to fenicsx 0.7.0. With version 0.7.0 vector quadrature elements do not behave as expected. Running the python example below with vector quadrature elements defined using quadrature_element(…) and VectorElement(…) results in the output:

new version:
array size scalar: 3072
array size vector: 3072

old version:
array size scalar: 3072
array size vector: 6144

For both definitions, I would expect the vector valued function to have twice as many dofs as the scalar function. Why isn’t that the case?

from dolfinx import (fem, mesh)
from basix.ufl import (quadrature_element)
from ufl import (FiniteElement, VectorElement)
from mpi4py import MPI


# common defintions
geoShape = "triangle"
degT = 2
degQ = degT
dim = 2

# mesh
msh = mesh.create_rectangle(comm=MPI.COMM_WORLD,
                            points=((0.0, 0.0), (2.0, 1.0)), n=(32, 16),
                            cell_type=mesh.CellType.triangle)

# new code -> not working as intended
quScaElem = quadrature_element(geoShape, (), "default", degQ)

quVecElem = quadrature_element(geoShape, (dim,), "default", degQ)



qu_1 = fem.functionspace(msh, quScaElem)
qu_2 = fem.functionspace(msh, quVecElem)

Fsca = fem.Function(qu_1)
Fvec = fem.Function(qu_2)

print("\nnew version:")
print("array size scalar: " + str(Fsca.x.array.size))
print("array size vector: " + str(Fvec.x.array.size))


# old code -> working as intended
quScaElem = FiniteElement(family = "Quadrature",
                             cell = geoShape,
                             degree = degQ,
                             quad_scheme="default")
quVecElem = VectorElement(quScaElem, dim)

qu_1 = fem.functionspace(msh, quScaElem)
qu_2 = fem.functionspace(msh, quVecElem)

Fsca = fem.Function(qu_1)
Fvec = fem.Function(qu_2)

print("\nold version:")
print("array size scalar: " + str(Fsca.x.array.size))
print("array size vector: " + str(Fvec.x.array.size))
2

This should be fixed by use blocked element when creating a quadrature element with value shape by mscroggs · Pull Request #711 · FEniCS/basix · GitHub. Thanks for pointing it out.

2 Likes
3

Thanks for your prompt reply. I installed the version from your branch and got my application working again.