FEniCS / ufl / 31370183750

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github

Committed by web-flow

Commit Message

Fix generic terminal traversal for BaseForm types in extract_domains (#502)

* Fix extract_domains for BaseForm to expand MeshSequence

The BaseForm-not-Expr branch added in #494 returned
expr.ufl_domains() directly, skipping the join_domains/sort_domains
call every other branch uses. BaseFunctionSpace.ufl_domains() does
not expand MeshSequence, so extract_domains(cofunction) on a mixed
dual space returned the raw MeshSequence instead of its component
meshes, unlike extract_domains(form) on the same space. Firedrake's
adjoint tape adds each extracted domain as a dependency, and a
MeshSequence is not an OverloadedType, so this crashed with
AttributeError: 'MeshSequenceGeometry' object has no attribute
'block_variable' when solving with a Cofunction RHS on a mixed
function space.

* Fix generic terminal traversal for ZeroBaseForm and Matrix

ZeroBaseForm, FormSum, Action, Adjoint and Matrix are BaseForm
subclasses that aren't also Expr subclasses, so ufl_type() never gives
them the _ufl_is_terminal_ trait (its Expr-specific branch returns
early for anything that isn't an Expr). traverse_unique_terminals
raised AttributeError on any of them, which is what the previous
commit's isinstance(expr, BaseForm) and not isinstance(expr, Expr)
special case in extract_domains was working around.

Give ZeroBaseForm _ufl_is_terminal_ = False (its operands are the
placeholder Arguments, real terminals worth descending into) and
Matrix _ufl_is_terminal_ = True (it's a genuine leaf, with domains and
arguments derived from its function spaces rather than any operand).
Matrix was also missing a ufl_domains() method entirely -- add it.

With those two fixed, extract_domains's generic branch no longer needs
the special case: route it through iter_expressions instead, the same
unwrapping algorithms/analysis.py's extract_type already uses to
decompose FormSum/Action/Adjoint (and Forms nested within them) down
to plain Expr trees and leaf BaseForms. Fall back to the bare expr ... (continued)

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