a = BilinearForm(basis, basis, bilinear_form=bilinear_form), is throwing a stack trace for this usage...

[prusso630]

from skfem import BilinearForm, CellBasis, ElementQuad1, MeshQuad1, asm
import numpy as np

# How to assemble a K matrix for the heat problem...

# Define the mesh
nodes = np.array([[0, 1, 1, 0], [0, 0, 1, 1]])
m = MeshQuad1(nodes)

# Define the basis
basis = CellBasis(m, ElementQuad1())

# Define the bilinear form a(v, w)
def bilinear_form(v, w):
    return np.sum(v.grad * w.grad)

# Define the linear form t(w)
def linear_form(w):
    return np.sum(w)

# Both of these ways of creating the BilinearForm are throwing a stack trace...
##a = BilinearForm(basis, basis, bilinear_form)
a = BilinearForm(basis, basis, bilinear_form=bilinear_form)
'''
Traceback (most recent call last):
  File "c:\Users\prusso\demo\scratchpad\scratchpad7.py", line 23, in <module>
    a = BilinearForm(basis, basis, bilinear_form=bilinear_form)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\prusso\demo\.venv\Lib\site-packages\skfem\assembly\form\form.py", line 39, in __init__
    self.nargs = (len(signature(self.form).parameters)
                      ^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python312\Lib\inspect.py", line 3327, in signature
    return Signature.from_callable(obj, follow_wrapped=follow_wrapped,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python312\Lib\inspect.py", line 3071, in from_callable
    return _signature_from_callable(obj, sigcls=cls,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python312\Lib\inspect.py", line 2484, in _signature_from_callable
    raise TypeError('{!r} is not a callable object'.format(obj))
TypeError: <skfem CellBasis(MeshQuad1, ElementQuad1) object>
  Number of elements: 1
  Number of DOFs: 4
  Size: 864 B is not a callable object
'''

'''
So far what I am trying to accomplish is the building of a K matrix. Globally
and in the local sense and/or a way to access the global K and local K once built...
So far the creation of the BilinearForm is the first hangup I have to get through...
'''
##t = LinearForm(basis, linear_form)
# Assemble the stiffness matrix K and the load vector b
##K = asm(a)
##b = asm(t)

I am attempting to create a bilinear form for this heat problem as Mark S. Gockenbach describes in his book Understanding The Finite Element Method. LaTeX's are attached. Anyone can help me why this stack trace so far?

[kinnala]

Did you try some of the example programs? They should demonstrate how BilinearForm wrapper is used. Also, the forms have too few arguments.

[kinnala]

Moreover, their return value has incorrect shape.