dolfin team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

Done and checked in. If someone updates FFC to support this, we can
hopefully close this bug.

Martin


On 8 June 2011 11:17, Martin Sandve Alnæs <martinal@xxxxxxxxx> wrote:
> Update: Of course the expand_indices algorithm does not handle your
> example where the tensor element is part of a mixed element. I'll
> consider adding symmetry as a property of all elements to fix this,
> that is much less work than adding it to all expressions.
>
> Martin
>
> On 8 June 2011 10:58, Martin Sandve Alnæs <martinal@xxxxxxxxx> wrote:
>> I checked out what UFL does. If you look at expand_indices.py,
>> you see that this algorithm does handle symmetries. However,
>> that algorithm is not (and should not be) used by all form compiler
>> variants. Here's a simplified version of the code:
>>
>>    def form_argument(self, x):
>>        if x.shape() == ():
>>            return x
>>        else:
>>            e = x.element()
>>
>>            # Get component
>>            c = self.component()
>>
>>            # Map it through the symmetry mapping
>>            if isinstance(e, TensorElement):
>>                s = e.symmetry() or {}
>>                c = s.get(c, c)
>>
>>            return x[c]
>>
>>
>> I want to make two points from this code:
>>
>> 1) The symmetry mapping is currently only available directly from a
>> TensorElement. Extending symmetries to be a property of all ufl
>> expressions could be quite a bit of work. If this is a wanted feature,
>> make a blueprint.
>>
>> 2) When you do have the symmetry mapping at hand, the mapping is
>> trivial. It should be a quick fix in FFC, just apply the symmetry
>> mapping like above everywhere you get the component of a form
>> argument.
>>
>> Martin
>>
>> 2011/4/5 Kristian B. Ølgaard <745646@xxxxxxxxxxxxxxxxxx>:
>>> The following simple form also fails:
>>>
>>> T1 = TensorElement('CG', triangle, 1, symmetry=True)
>>> T2 = TensorElement('CG', triangle, 1, symmetry=True)
>>> TT = T1*T2
>>> P, Q = Coefficients(TT)
>>> M = inner(P, Q)*dx
>>> print M
>>>
>>> Printing 'M' results in:
>>>
>>> { ([[
>>>  [ (w_0)[0], (w_0)[1] ],
>>>  [ (w_0)[1], (w_0)[3] ]
>>> ]]) : ([[
>>>  [ (w_0)[4], (w_0)[5] ],
>>>  [ (w_0)[5], (w_0)[7] ]
>>> ]]) } * dx0
>>>
>>> which illustrates the problem in FFC for both tensor and quadrature representations.
>>> The component '7' in the ListTensor does not exist in the MixedElement of FFC which, due to symmetry, only contain 6 'unique' subelements (components).
>>> One could argue that UFL should keep track of symmetry when creating the indices of list tensors such that it maps 3->2, 4->3, 5->4 and 7->6.
>>>
>>> --
>>> You received this bug notification because you are a member of DOLFIN
>>> Team, which is subscribed to DOLFIN.
>>> https://bugs.launchpad.net/bugs/745646
>>>
>>> Title:
>>>  Problem with assemble() with MixedFunctionSpace of symmetric
>>>  TensorFunctionSpaces
>>>
>>> Status in DOLFIN:
>>>  New
>>>
>>> Bug description:
>>>  from dolfin import *
>>>
>>>  mesh = Rectangle(0,0,1,1,10,10)
>>>  dim = 2 #assume 2D
>>>  symm = dict(((i,j), (j,i))
>>>              for i in range(dim) for j in range(dim) if i > j )
>>>
>>>  T1 = TensorFunctionSpace(mesh, 'CG', 1, symmetry=symm)
>>>  T2 = TensorFunctionSpace(mesh, 'CG', 1, symmetry=symm)
>>>
>>>  TT = T1*T2
>>>
>>>  R, S = TrialFunctions(TT)
>>>  v_R, v_S = TestFunctions(TT)
>>>
>>>  P = Function(T1)
>>>  Q = Function(T2)
>>>
>>>  Fr = inner(R,v_R)*dx+ inner(P,v_R)*dx
>>>
>>>  Fs = inner( S, v_S )*dx + inner( Q, v_S )*dx
>>>
>>>  F = Fr + Fs
>>>
>>>  A = lhs(F)
>>>  B = rhs(F)
>>>
>>>  a = Matrix()
>>>  a = assemble(A, tensor=a)
>>>  b = Vector()
>>>  b = assemble(B, tensor=b)
>>>
>>>  I get the following error:
>>>
>>>  Calling FFC just-in-time (JIT) compiler, this may take some time.
>>>  Traceback (most recent call last):
>>>    File "tensortest2.py", line 28, in <module>
>>>      a = assemble(A, tensor=a)
>>>    File "/usr/lib/python2.6/dist-packages/dolfin/fem/assemble.py", line 100, in assemble
>>>      common_cell=common_cell)
>>>    File "/usr/lib/python2.6/dist-packages/dolfin/fem/form.py", line 34, in __init__
>>>      (self._compiled_form, module, self.form_data) = jit(form, form_compiler_parameters, common_cell)
>>>    File "/usr/lib/python2.6/dist-packages/dolfin/compilemodules/jit.py", line 47, in mpi_jit
>>>      return local_jit(*args, **kwargs)
>>>    File "/usr/lib/python2.6/dist-packages/dolfin/compilemodules/jit.py", line 114, in jit
>>>      return jit_compile(form, parameters=p, common_cell=common_cell)
>>>    File "/usr/lib/python2.6/dist-packages/ffc/jitcompiler.py", line 64, in jit
>>>      return jit_form(object, parameters, common_cell)
>>>    File "/usr/lib/python2.6/dist-packages/ffc/jitcompiler.py", line 122, in jit_form
>>>      compile_form(preprocessed_form, prefix=jit_object.signature(), parameters=parameters)
>>>    File "/usr/lib/python2.6/dist-packages/ffc/compiler.py", line 140, in compile_form
>>>      ir = compute_ir(analysis, parameters)
>>>    File "/usr/lib/python2.6/dist-packages/ffc/representation.py", line 66, in compute_ir
>>>      irs = [_compute_integral_ir(f, i, parameters) for (i, f) in enumerate(forms)]
>>>    File "/usr/lib/python2.6/dist-packages/ffc/representation.py", line 186, in _compute_integral_ir
>>>      parameters)
>>>    File "/usr/lib/python2.6/dist-packages/ffc/tensor/tensorrepresentation.py", line 59, in compute_integral_ir
>>>      ir["AK"] = _compute_terms(monomial_form, None, None, domain_type, quadrature_degree)
>>>    File "/usr/lib/python2.6/dist-packages/ffc/tensor/tensorrepresentation.py", line 98, in _compute_terms
>>>      quadrature_degree)
>>>    File "/usr/lib/python2.6/dist-packages/ffc/tensor/referencetensor.py", line 28, in __init__
>>>      self.A0 = integrate(monomial, domain_type, facet0, facet1, quadrature_order)
>>>    File "/usr/lib/python2.6/dist-packages/ffc/tensor/monomialintegration.py", line 50, in integrate
>>>      psis = [_compute_psi(v, table, len(points), domain_type) for v in monomial.arguments]
>>>    File "/usr/lib/python2.6/dist-packages/ffc/tensor/monomialintegration.py", line 169, in _compute_psi
>>>      Psi[component][tuple(dlist)] = etable[dtuple][:, cindex[0].index_range[component], :]
>>>
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>>
>