def assemble(self):
"""Actually assemble this :class:`Matrix`.
This calls the stashed assembly callback or does nothing if
the matrix is already assembled.
.. note::
If the boundary conditions stashed on the :class:`Matrix` have
changed since the last time it was assembled, this will
necessitate reassembly. So for example:
.. code-block:: python
A = assemble(a, bcs=[bc1])
solve(A, x, b)
bc2.apply(A)
solve(A, x, b)
will apply boundary conditions from `bc1` in the first
solve, but both `bc1` and `bc2` in the second solve.
"""
if self._assembly_callback is None:
raise RuntimeError('Trying to assemble a Matrix, but no thunk found')
if self._assembled:
if self._needs_reassembly:
solving._assemble(self.a, tensor=self, bcs=self.bcs)
return self.assemble()
return
self._bcs_at_point_of_assembly = copy.copy(self.bcs)
self._assembly_callback(self.bcs)
self._assembled = True
def _form_action(self, u):
"""Assemble the form action of this :class:`Matrix`' bilinear form
onto the :class:`Function` ``u``.
.. note::
This is the form **without** any boundary conditions."""
if not hasattr(self, '_a_action'):
self._a_action = ufl.action(self._a, u)
if hasattr(self, '_a_action_coeff'):
self._a_action = ufl.replace(self._a_action, {self._a_action_coeff: u})
self._a_action_coeff = u
# Since we assemble the cached form, the kernels will already have
# been compiled and stashed on the form the second time round
return solving._assemble(self._a_action)
