Time-dependent BC

dolfinx
1

I would like to define time-dependent BC on a scalar FEM space. Here is a MWE:

from mpi4py import MPI
import numpy as np
import ufl
from basix.ufl import element
from dolfinx.fem import (Function, dirichletbc, functionspace, locate_dofs_topological, locate_dofs_geometrical,)
from dolfinx.mesh import *

# mesh, spaces, functions
msh = create_unit_square(MPI.COMM_WORLD, 10,10)
P1 = element("Lagrange", "triangle", 1) 
XV = functionspace(msh, P1)
x = ufl.SpatialCoordinate(msh)

# BC
def Gamma(x):
    return np.isclose(x[0], 0.)

class time_dep_func:
    def __init__(self):
        self.t = 0.0

    def eval(self, x):
        return np.sin(self.t)

BC_obj = time_dep_func()
BC_obj.t = 0.
bc_fun = Function(XV) 
bc_fun.interpolate(BC_obj.eval)

dofs = locate_dofs_geometrical(XV, Gamma) 
bcu = dirichletbc(bc_fun, dofs, XV)

I get an error message like this:

Traceback (most recent call last):
  File "/home/renoldner/miniconda3/envs/fenicsx/lib/python3.11/site-packages/dolfinx/fem/function.py", line 397, in interpolate
    _interpolate(u, cells)
  File "/home/renoldner/miniconda3/envs/fenicsx/lib/python3.11/functools.py", line 909, in wrapper
    return dispatch(args[0].__class__)(*args, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/renoldner/miniconda3/envs/fenicsx/lib/python3.11/site-packages/dolfinx/fem/function.py", line 373, 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 0x7f6542b703f0>, <bound method time_dep_func.eval of <__main__.time_dep_func object at 0x7f6546dd34d0>>, 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 "/home/ [...] / test.py", line 34, in <module>
    bc_fun.interpolate(BC_obj.eval)
  File "/home/renoldner/miniconda3/envs/fenicsx/lib/python3.11/site-packages/dolfinx/fem/function.py", line 402, in interpolate
    self._cpp_object.interpolate(np.asarray(u(x), dtype=self.dtype), cells)
IndexError: invalid axis: 0 (ndim = 0)

I can not explain this, as in THIS DISCOURSE POST, the method seems to work (however, there, a Vector-valued FEM space is used).

Using
dofs = locate_dofs_topological(XV, 1, Gamma)

does not fix the error.

2

Hello there,

My best guess after rapidly reading your code is that there’s something wrong in the definition of eval and, consequently, in the line bc_fun.interpolate(BC_obj.eval).

If you make eval actually depend on x (like, for instance, by returning x[0]**2*np.sin(self.t)) it should pass the interpolation line with no error. Then it could complain for the locate_dofs_geometrical args but I’m not sure because I didn’t run your code.

All the best,
Giorgia

1 Like
3

Thank you for your answer. I tried the following:

class time_dep_func:
    def __init__(self):
        self.t = 0.0

    def eval(self, x):
        return x[0]**2*np.sin(self.t)

with “locate_dofs_geometricl” and get

python3 test.py 
Traceback (most recent call last):
  File "/home/renoldner/miniconda3/envs/fenicsx/lib/python3.11/site-packages/dolfinx/fem/bcs.py", line 175, in dirichletbc
    bc = bctype(_value, dofs, V)
         ^^^^^^^^^^^^^^^^^^^^^^^
TypeError: __init__(): incompatible constructor arguments. The following argument types are supported:
    1. dolfinx.cpp.fem.DirichletBC_float64(g: numpy.ndarray[numpy.float64], dofs: numpy.ndarray[numpy.int32], V: dolfinx::fem::FunctionSpace<double>)
    2. dolfinx.cpp.fem.DirichletBC_float64(g: dolfinx::fem::Constant<double>, dofs: numpy.ndarray[numpy.int32], V: dolfinx::fem::FunctionSpace<double>)
    3. dolfinx.cpp.fem.DirichletBC_float64(g: dolfinx::fem::Function<double, double>, dofs: numpy.ndarray[numpy.int32])
    4. dolfinx.cpp.fem.DirichletBC_float64(g: dolfinx::fem::Function<double, double>, dofs: Annotated[List[numpy.ndarray[numpy.int32]], FixedSize(2)], V: dolfinx::fem::FunctionSpace<double>)

Invoked with: <dolfinx.cpp.fem.Function_float64 object at 0x7f154cbcabf0>, array([ 64,  66,  76,  85,  93, 100, 106, 111, 115, 118, 120], dtype=int32), FunctionSpace(Mesh(blocked element (Basix element (P, triangle, 1, gll_warped, unset, False), (2,)), 0), Basix element (P, triangle, 1, gll_warped, unset, False))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/ [...] / test.py", line 34, in <module>
    bcu = dirichletbc(bc_fun, dofs, XV)     
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/renoldner/miniconda3/envs/fenicsx/lib/python3.11/site-packages/dolfinx/fem/bcs.py", line 177, in dirichletbc
    bc = bctype(_value, dofs, V._cpp_object)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: __init__(): incompatible constructor arguments. The following argument types are supported:
    1. dolfinx.cpp.fem.DirichletBC_float64(g: numpy.ndarray[numpy.float64], dofs: numpy.ndarray[numpy.int32], V: dolfinx::fem::FunctionSpace<double>)
    2. dolfinx.cpp.fem.DirichletBC_float64(g: dolfinx::fem::Constant<double>, dofs: numpy.ndarray[numpy.int32], V: dolfinx::fem::FunctionSpace<double>)
    3. dolfinx.cpp.fem.DirichletBC_float64(g: dolfinx::fem::Function<double, double>, dofs: numpy.ndarray[numpy.int32])
    4. dolfinx.cpp.fem.DirichletBC_float64(g: dolfinx::fem::Function<double, double>, dofs: Annotated[List[numpy.ndarray[numpy.int32]], FixedSize(2)], V: dolfinx::fem::FunctionSpace<double>)

Invoked with: <dolfinx.cpp.fem.Function_float64 object at 0x7f154cbcabf0>, array([ 64,  66,  76,  85,  93, 100, 106, 111, 115, 118, 120], dtype=int32), <dolfinx.cpp.fem.FunctionSpace_float64 object at 0x7f1548988f70>

The arguments of locate_dofs_geometrical look correct to me, i have successfully used them like this in other scripts.

4

It’s actually complaining when calling dirichletbc, locate_dofs_geometrical is working correctly. Try to take a look at the error here:

TypeError: __init__(): incompatible constructor arguments. The following argument types are supported:
    1. dolfinx.cpp.fem.DirichletBC_float64(g: numpy.ndarray[numpy.float64], dofs: numpy.ndarray[numpy.int32], V: dolfinx::fem::FunctionSpace<double>)
    2. dolfinx.cpp.fem.DirichletBC_float64(g: dolfinx::fem::Constant<double>, dofs: numpy.ndarray[numpy.int32], V: dolfinx::fem::FunctionSpace<double>)
    3. dolfinx.cpp.fem.DirichletBC_float64(g: dolfinx::fem::Function<double, double>, dofs: numpy.ndarray[numpy.int32])
    4. dolfinx.cpp.fem.DirichletBC_float64(g: dolfinx::fem::Function<double, double>, dofs: Annotated[List[numpy.ndarray[numpy.int32]], FixedSize(2)], V: dolfinx::fem::FunctionSpace<double>)

Invoked with: <dolfinx.cpp.fem.Function_float64 object at 0x7f154cbcabf0>, array([ 64,  66,  76,  85,  93, 100, 106, 111, 115, 118, 120], dtype=int32), FunctionSpace(Mesh(blocked element (Basix element (P, triangle, 1, gll_warped, unset, False), (2,)), 0), Basix element (P, triangle, 1, gll_warped, unset, False))
1 Like
5

In addition to the previous change by @gpase, you should also be changing the very final line ot

bcu = dirichletbc(bc_fun, dofs)

The third argument is only needed when the first input argument is a constant (or when the FE space is a mixed one). In this case, bc_fun is a function, so dirichletbc already knows from that that XV is the FE space to be used when extracting DOFs.

6

Thank you for your answer!