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["Johan Hake" <hake@xxxxxxxxx>]

>
>
> Andy Ray Terrel wrote:
>> Hello,
>>
>> I'm still getting a hang of this but I was trying to do some things
>> with mixed elements and derivatives.  I'm not sure if I have the bug
>> or if ufl has a bug but the following doesn't pass ufl-analyse.
>>
>>
>> sElem = TensorElement("DG", triangle, 1)
>> vElem = VectorElement("CG", triangle, 2)
>>
>> mElem = sElem + vElem
>>
>> phi, v = TestFunctions(mElem)
>> sigma, u = TrialFunctions(mElem)
>>
>
> The above is the problem. You need to use 'split'. Look at the
> cahn-hilliard demo for an example of how to do it.
>
> Garth
>
>> sF = Function(sElem)

I might be totaly of here but does not TestFunctions and TrialFunctions
return a properly splitted FooFunction?

What I mean is:

  dk, dc = TestFunctions(ME)

should be the same as:

  du = TestFunction(ME)
  dk, dc = split(du)

Please correct me if I am wrong.

Isn't the problem the sF Function, which is defined using an element which
is not 'properly mixed'?

>> f = inner(sF, dot(u, grad(sF)))*dx
>> F = derivative(f, sF, phi)
>> J = derivative(F, sF, sigma)
>>
>>
>> It seems that the TestFunctions function doesn't return a proper
>> TestFunction but a list of things.

I think the list you refere to is the somewhat unreadable representation
of the view of the TestFunctions, which should be the correct one.

Johan

> I can do the following but then I
>> loose the mixed element, which I don't know if ffc could handle.
>>
>>
>> sElem = TensorElement("DG", triangle, 1)
>> vElem = VectorElement("CG", triangle, 2)
>>
>> mElem = sElem + vElem
>>
>> phi = TestFunction(sElem)
>> v = TestFunction(vElem)
>> sigma = TrialFunction(sElem)
>> u = TrialFunction(vElem)
>>
>> sF = Function(sElem)
>>
>> f = inner(sF, dot(u, grad(sF)))*dx
>> F = derivative(f, sF, phi)
>> J = derivative(F, sF, sigma)
>>
>>
>> Any thoughts on either my bug or ufl please let me know.
>>
>> -- Andy
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>
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