Adjoint: only skip expand_derivatives if necessary

firedrakeproject · Jan 4, 2025 · 5894b49 · 5894b49
1 parent 6078f93
commit 5894b49
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/firedrake/adjoint_utils/variational_solver.py b/firedrake/adjoint_utils/variational_solver.py
@@ -21,7 +21,12 @@ def wrapper(self, *args, **kwargs):
                 # Some forms (e.g. SLATE tensors) are not currently
                 # differentiable.
                 dFdu = derivative(self.F, self.u_restrict)
-                self._ad_adj_F = adjoint(dFdu, derivatives_expanded=True)
+                try:
+                    self._ad_adj_F = adjoint(dFdu)
+                except ValueError:
+                    # Try again without expanding derivatives,
+                    # as dFdu might have been simplied to an empty Form
+                    self._ad_adj_F = adjoint(dFdu, derivatives_expanded=True)
             except (TypeError, NotImplementedError):
                 self._ad_adj_F = None
             self._ad_kwargs = {'Jp': self.Jp, 'form_compiler_parameters': self.form_compiler_parameters, 'is_linear': self.is_linear}