*Real FS* Mixed FS instantiation with >2 spaces fails when some FS is Real

[dorugeber]

from firedrake import *

mesh = PeriodicUnitIntervalMesh(10)

V1 = FunctionSpace(mesh, "CG", 1)
V2 = TensorFunctionSpace(mesh, "CG", 1)
V3 = FunctionSpace(mesh, "Real", 0)
V = V2*V3  # lives
V = V1*V2*V1  # lives
V = V1*V2*V3  # dies

fails with

Traceback (most recent call last):
  File "bug.py", line 10, in <module>
    V = V1*V2*V3  # dies
  File "/home/andrew/firedrake/src/firedrake/firedrake/functionspaceimpl.py", line 203, in __mul__
    return MixedFunctionSpace((self, other))
  File "/home/andrew/firedrake/src/firedrake/firedrake/functionspace.py", line 258, in MixedFunctionSpace
    new = impl.MixedFunctionSpace(spaces, name=name)
  File "/home/andrew/firedrake/src/firedrake/firedrake/functionspaceimpl.py", line 529, in __init__
    self.comm = self.node_set.comm
  File "/home/andrew/firedrake/src/PyOP2/pyop2/utils.py", line 64, in __get__
    obj.__dict__[self.__name__] = result = self.fget(obj)
  File "/home/andrew/firedrake/src/firedrake/firedrake/functionspaceimpl.py", line 622, in node_set
    return op2.MixedSet(s.node_set for s in self._spaces)
  File "/home/andrew/firedrake/src/PyOP2/pyop2/backends.py", line 118, in __call__
    return t(*args, **kwargs)
  File "/home/andrew/firedrake/src/PyOP2/pyop2/caching.py", line 156, in __new__
    obj = make_obj()
  File "/home/andrew/firedrake/src/PyOP2/pyop2/caching.py", line 137, in make_obj
    obj.__init__(*args, **kwargs)
  File "/home/andrew/firedrake/src/PyOP2/pyop2/base.py", line 979, in __init__
    self.comm = reduce(lambda a, b: a if a is None else a.comm or b if b is None else b.comm, sets)
  File "/home/andrew/firedrake/src/PyOP2/pyop2/base.py", line 979, in <lambda>
    self.comm = reduce(lambda a, b: a if a is None else a.comm or b if b is None else b.comm, sets)
AttributeError: 'mpi4py.MPI.Intracomm' object has no attribute 'comm'

[dorugeber]

Suggestion from @miklos1:
self.comm = reduce(lambda a, b: a or b, map(lambda s: s if s is None else s.comm, sets))

[dorugeber]

Similar problem in the iterset when doing a (linear or nonlinear) solve:

from firedrake import *

mesh = UnitIntervalMesh(10)
parameters["pyop2_options"]["lazy_evaluation"] = False

V1 = FunctionSpace(mesh, "CG", 1)
V2 = FunctionSpace(mesh, "CG", 2)
V3 = FunctionSpace(mesh, "Real", 0)

V = V1*V2*V3

abc = Function(V)
a, b, c = split(abc)
d, e, f = TestFunctions(V)

F = (a*d + b*e + c*f)*dx

solve(F == 0, abc)

Traceback (most recent call last):
  File "bug.py", line 18, in <module>
    solve(F == 0, abc)
  File "/home/andrew/firedrake/src/firedrake/firedrake/solving.py", line 119, in solve
    _solve_varproblem(*args, **kwargs)
  File "/home/andrew/firedrake/src/firedrake/firedrake/solving.py", line 162, in _solve_varproblem
    options_prefix=options_prefix)
  File "/home/andrew/firedrake/src/firedrake/firedrake/variational_solver.py", line 127, in __init__
    ctx = solving_utils._SNESContext(problem, pre_jacobian_callback, pre_function_callback)
  File "/home/andrew/firedrake/src/firedrake/firedrake/solving_utils.py", line 111, in __init__
    for problem in problems)
  File "/home/andrew/firedrake/src/firedrake/firedrake/solving_utils.py", line 111, in <genexpr>
    for problem in problems)
  File "/home/andrew/firedrake/src/firedrake/firedrake/assemble.py", line 67, in assemble
    inverse=inverse, nest=nest)
  File "<decorator-gen-294>", line 2, in _assemble
  File "/home/andrew/firedrake/src/firedrake/firedrake/utils.py", line 62, in wrapper
    return f(*args, **kwargs)
  File "/home/andrew/firedrake/src/firedrake/firedrake/assemble.py", line 163, in _assemble
    map_pairs.append((op2.DecoratedMap(test.cell_node_map(), cell_domains),
  File "/home/andrew/firedrake/src/firedrake/firedrake/functionspaceimpl.py", line 646, in cell_node_map
    for i, s in enumerate(self._spaces))
  File "/home/andrew/firedrake/src/PyOP2/pyop2/backends.py", line 118, in __call__
    return t(*args, **kwargs)
  File "/home/andrew/firedrake/src/PyOP2/pyop2/caching.py", line 156, in __new__
    obj = make_obj()
  File "/home/andrew/firedrake/src/PyOP2/pyop2/caching.py", line 137, in make_obj
    obj.__init__(*args, **kwargs)
  File "/home/andrew/firedrake/src/PyOP2/pyop2/base.py", line 3342, in __init__
    if not all(m is None or m.iterset == self.iterset for m in self._maps):
  File "/home/andrew/firedrake/src/PyOP2/pyop2/base.py", line 3342, in <genexpr>
    if not all(m is None or m.iterset == self.iterset for m in self._maps):
  File "/home/andrew/firedrake/src/PyOP2/pyop2/utils.py", line 64, in __get__
    obj.__dict__[self.__name__] = result = self.fget(obj)
  File "/home/andrew/firedrake/src/PyOP2/pyop2/base.py", line 3366, in iterset
    return reduce(lambda a, b: a if a is None else a.iterset or b if b is None else b.iterset, self._maps)
  File "/home/andrew/firedrake/src/PyOP2/pyop2/base.py", line 3366, in <lambda>
    return reduce(lambda a, b: a if a is None else a.iterset or b if b is None else b.iterset, self._maps)
AttributeError: 'Set' object has no attribute 'iterset'

Suggested patch: return reduce(lambda a, b: a or b, map(lambda s: s if s is None else s.iterset, self._maps))

[colinjcotter]

@dorugeber any chance you could try those patches and see if it works?

[dorugeber]

What?

[colinjcotter]

You wrote "suggested patch" etc

[dorugeber]

Yes. Those patches make those snippets of code work. The code I wanted to run then failed, per #863

[colinjcotter]

OK thanks for clarifying. Code in #863 is not expected to work.

[miklos1]

@dorugeber: What's the state of this? Are the suggested patches in master yet, and can this be closed?

[wence-]

Seems to work now.