Interpolation into Quadrature (non-basix) element

[michalhabera]

Elements which are not registered in basix, but still interpolatory, could prepare interpolation points and interpolation matrix during element construction in FiniteElement.cpp.
For Quadrature element this requires quadrature scheme provided from FFCx generated code, or better, a "variant".

[garth-wells]

@michalhabera , @mscroggs is this still an issue with all the recent changes?

[jorgensd]

Still an issue:

import dolfinx
import basix.ufl
from mpi4py import MPI

def f(x):
    return x[0]

mesh = dolfinx.mesh.create_unit_square(MPI.COMM_WORLD, 10, 10)
el = basix.ufl.quadrature_element(mesh.topology.cell_name(), value_shape=(),scheme="default", degree=1)
V = dolfinx.fem.functionspace(mesh, el)
u = dolfinx.fem.Function(V)
u.interpolate(f)

returns

root@dokken-XPS-9320:~/shared# python3 mwe.py 
Traceback (most recent call last):
  File "/usr/local/dolfinx-real/lib/python3.10/dist-packages/dolfinx/fem/function.py", line 396, in interpolate
    _interpolate(u, cells)
  File "/usr/lib/python3.10/functools.py", line 889, in wrapper
    return dispatch(args[0].__class__)(*args, **kw)
  File "/usr/local/dolfinx-real/lib/python3.10/dist-packages/dolfinx/fem/function.py", line 372, in _interpolate
    self._cpp_object.interpolate(u, cells, nmm_interpolation_data)
TypeError: interpolate(): incompatible function arguments. The following argument types are supported:
    1. (self: dolfinx.cpp.fem.Function_float64, f: numpy.ndarray[numpy.float64], cells: numpy.ndarray[numpy.int32]) -> None
    2. (self: dolfinx.cpp.fem.Function_float64, u: dolfinx.cpp.fem.Function_float64, cells: numpy.ndarray[numpy.int32], nmm_interpolation_data: Tuple[List[int], List[int], List[float], List[int]]) -> None
    3. (self: dolfinx.cpp.fem.Function_float64, expr: dolfinx::fem::Expression<double, double>, cells: numpy.ndarray[numpy.int32]) -> None

Invoked with: <dolfinx.cpp.fem.Function_float64 object at 0x7fce44b32030>, <function f at 0x7fce523c3d90>, array([  0,   1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,
        13,  14,  15,  16,  17,  18,  19,  20,  21,  22,  23,  24,  25,
        26,  27,  28,  29,  30,  31,  32,  33,  34,  35,  36,  37,  38,
        39,  40,  41,  42,  43,  44,  45,  46,  47,  48,  49,  50,  51,
        52,  53,  54,  55,  56,  57,  58,  59,  60,  61,  62,  63,  64,
        65,  66,  67,  68,  69,  70,  71,  72,  73,  74,  75,  76,  77,
        78,  79,  80,  81,  82,  83,  84,  85,  86,  87,  88,  89,  90,
        91,  92,  93,  94,  95,  96,  97,  98,  99, 100, 101, 102, 103,
       104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116,
       117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129,
       130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142,
       143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155,
       156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168,
       169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181,
       182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194,
       195, 196, 197, 198, 199], dtype=int32), ((), (), (), ())

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/root/shared/mwe.py", line 12, in <module>
    u.interpolate(f)
  File "/usr/local/dolfinx-real/lib/python3.10/dist-packages/dolfinx/fem/function.py", line 400, in interpolate
    x = _cpp.fem.interpolation_coords(self._V.element, self._V.mesh.geometry, cells)
RuntimeError: Cannot get interpolation points - no Basix element available. Maybe this is a mixed element?

[clementberger]

When will the fix be publicly available ? I upgraded to the latest version available in conda (dolfinx 0.7.2) and the issue remains the same.

[jorgensd]

When will the fix be publicly available ? I upgraded to the latest version available in conda (dolfinx 0.7.2) and the issue remains the same.

I guess the question is when will this be available on conda (i.e. when do we plan a new release).
I think there are a few things in the works at the moment, see: https://github.com/FEniCS/dolfinx/milestone/8
As long as no more milestones will be added, I guess a release within the end of February seems likely.