Quadrature element

Question

In the newest version of FeNiCs, I don't seems to be able to call

DG = VectorFunctionSpace(mesh, "Quadrature", degree=2)

Missing quad_scheme in quadrature element.
Traceback (most recent call last):
File "ArtsActive_v5.py", line 272, in
DG = VectorFunctionSpace(mesh, "Quadrature", degree=2)
File "/usr/lib/python2.7/dist-packages/dolfin/functions/functionspace.py", line 553, in VectorFunctionSpace
constrained_domain=constrained_domain)
File "/usr/lib/python2.7/dist-packages/dolfin/functions/functionspace.py", line 206, in init
self._init_from_ufl(*args, **kwargs)
File "/usr/lib/python2.7/dist-packages/dolfin/functions/functionspace.py", line 226, in _init_from_ufl
dolfin_element, dolfin_dofmap = _compile_dolfin_element(element, mesh, constrained_domain=constrained_domain)
File "/usr/lib/python2.7/dist-packages/dolfin/functions/functionspace.py", line 89, in _compile_dolfin_element
ufc_element, ufc_dofmap = jit(element, mpi_comm=mesh.mpi_comm())
File "/usr/lib/python2.7/dist-packages/dolfin/compilemodules/jit.py", line 65, in mpi_jit
return local_jit(*args, **kwargs)
File "/usr/lib/python2.7/dist-packages/dolfin/compilemodules/jit.py", line 143, in jit
return form_compiler.jit(form, parameters=p)
File "/usr/local/lib/python2.7/dist-packages/FFC-1.7.0dev-py2.7.egg/ffc/jitcompiler.py", line 119, in jit
parameters=parameters, jit=True)
File "/usr/local/lib/python2.7/dist-packages/FFC-1.7.0dev-py2.7.egg/ffc/compiler.py", line 204, in compile_element
analysis = analyze_elements(elements, parameters)
File "/usr/local/lib/python2.7/dist-packages/FFC-1.7.0dev-py2.7.egg/ffc/analysis.py", line 99, in analyze_elements
error("Missing quad_scheme in quadrature element.")
File "", line 1, in
File "build/bdist.linux-x86_64/egg/ufl/log.py", line 158, in error
Exception: Missing quad_scheme in quadrature element.

Any help would be greatly appreciated!
Thanks!

Comments

Hi, see the penultimate comment in this thread for the answer.

---

Thanks Mirok! I saw that comment before. But I still don't quite know how to interpolate a field onto the quadrature function space.

For example, I have a field defined as

 DGfine = VectorFunctionSpace(finemesh, "DG", 0)
 field = Function(DGfine, 'field.xml')

and I want to interpolate to a quadrature functional space and I used to be able to do that using

Quad = VectorFunctionSpace(mesh, "Quadrature", 2)
fieldQuad = interpolate(field, Quad)

but this seems not possible in v1.7

---

I confirm there seems to be some issue here. This works:

import dolfin
mesh = dolfin.UnitSquareMesh(1,1)
fe = dolfin.FiniteElement(family="Quadrature", cell=mesh.ufl_cell(), degree=1, quad_scheme="default")
fs = dolfin.FunctionSpace(mesh, fe) # can't use keyword arguments here

However, this does not (Exception: Missing quad_scheme in quadrature element):

import dolfin
mesh = dolfin.UnitSquareMesh(1,1)
fs = dolfin.FunctionSpace(mesh, "Quadrature", 1) # can't use keyword arguments here

Similarly, this does not work (Exception: Missing quad_scheme in quadrature element):

import dolfin
mesh = dolfin.UnitSquareMesh(1,1)
vfs = dolfin.VectorFunctionSpace(mesh, "Quadrature", 1) # can't use keyword arguments here

Any hint? Thanks!

Answer 1

Hi! This code runs fine on the 2016.1 version:

from dolfin import *
mesh = UnitSquareMesh(4,4)

quad_element = VectorElement(family = "Quadrature",
                             cell = mesh.ufl_cell(),
                             degree = 2,
                             quad_scheme="default")

Quad = FunctionSpace(mesh, quad_element)

finemesh = adapt(mesh)
DGfine = VectorFunctionSpace(finemesh, "DG", 0)
field = Function(DGfine)

q = interpolate(field, Quad)