dolfin team mailing list archive

[Kristian Ølgaard <k.b.oelgaard@xxxxxxxxx>]

On 8 June 2011 12:11, Martin Sandve Alnæs <martinal@xxxxxxxxx> wrote:
> Done and checked in. If someone updates FFC to support this, we can
> hopefully close this bug.

I'm not sure this is enough to handle the bug. If you look at the
output of printing M in the example code I posted you'll see that the
list tensor contains component '7'. This is what you'll get from
calling self.component(), but the
TT.symmetry() only contains:
{(2,): (1,), (6,): (5,)}

Is there some function we need to call first to map the component '7'
--> '6', before looking at symmetries to map '6' --> '5'?
Doing so will get us into trouble with mapping '3' --> '2' since
symmetry will map that to '1'.
The TT element has 2 x 3 sub elements due to symmetry.

Kristian

> 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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>>>
>>
>
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