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RieszMap fixes/suggestions #4568

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8a72a28
RieszMap boundary condition fixes
jrmaddison Sep 18, 2025
9d5b85c
Remove extra Function instantiation
jrmaddison Sep 18, 2025
c04f182
Zero guess the RieszMap solver
jrmaddison Sep 18, 2025
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16 changes: 14 additions & 2 deletions firedrake/cofunction.py
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Original file line number Diff line number Diff line change
Expand Up @@ -426,6 +426,13 @@ def __init__(self, function_space_or_inner_product=None,
sobolev_space, u, v
)

if bcs is None:
bcs = ()
else:
bcs = tuple(bcs)
if len(bcs) > 0 and inner_product == "l2":
raise ValueError("Cannot supply boundary conditions with an l2 Riesz map")
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I'm curious here. Does this lead to the wrong results in optimization?

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Does "l2" here means that we are imposing the wrong inner-product between two primal objects, or does it mean that we are pairing a primal with a dual?

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I'm curious here. Does this lead to the wrong results in optimization?

For $l_2$ the bcs are ignored. They could probably be applied, but I'm not sure it would be that useful.

Does "l2" here means that we are imposing the wrong inner-product between two primal objects, or does it mean that we are pairing a primal with a dual?

Yes, it's the basis dependent map defined by dof assignment. I'm not sure if there's a case to remove this now (Firedrake code at least doesn't seem to use it much?) but maybe not for this PR?

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@JHopeCollins JHopeCollins Sep 26, 2025 •
edited
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I'm not sure if there's a case to remove this now (Firedrake code at least doesn't seem to use it much?) but maybe not for this PR?

This close to a major release I'd say lets keep this PR to fixes, then we can think about API changes after.


self._function_space = function_space
self._inner_product = inner_product
self._bcs = bcs
Expand Down Expand Up @@ -478,8 +485,8 @@ def __call__(self, value):
else:
solve, rhs, soln = self._solver
rhs.assign(value)
soln.zero()
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Doesn't PETSc always use a zero initial guess unless you pass -ksp_initial_guess_nonzero?

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This might be ignored due to #4142. I'd need to check for this use case, but I think it's still safer to zero here.

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@pbrubeck pbrubeck Sep 26, 2025 •
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LinearSolver inherits from NonlinearVariationalSolver, which means that we are running a SNES, which gives a different behaivor from the plain KSP. Currently -ksp_initial_guess_nonzero False zeros the update to whatever is prescribed as the initial guess.

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Setting the initial guess explicitly outside PETSc is the only way with SNES.

solve()
output = Function(self._function_space)
output.assign(soln)
elif ufl.duals.is_primal(value):
if value.function_space() != self._function_space:
Expand All @@ -490,8 +497,13 @@ def __call__(self, value):
for o, c in zip(output.subfunctions, value.subfunctions):
o.dat.data[:] = c.dat.data_ro[:]
else:
if len(self._bcs) > 0:
value = value.copy(deepcopy=True)
for bc in self._bcs:
bc.apply(value)
output = firedrake.assemble(
firedrake.action(self._inner_product, value)
firedrake.action(self._inner_product, value),
bcs=self._bcs, zero_bc_nodes=True,
)
else:
raise ValueError(
Expand Down
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