dolfin team mailing list archive

["Alessio Quaglino" <alessio@xxxxxx>]

Ok very simple thanks (I thought it might have been dependent to the
finite element shape). I still have one question about the new Funcion
interface. When I define a User-defined Function, only eval() is used for
the FEM assembly? I ask this because I have some problems in understanding
if overloading this method is enough in order to define a source term.
Also this method is defined as const, hence if this happens to be the
case, I have to redisign a part of my source class. Thanks.

Alessio


> Just do the following:
>
> Mesh mesh; Function f;
>
> real* vertex_values = new real[mesh.numVertices()];
> f.interpolate(vertex_values);
>
> Then vertex_values will be an array with the values at all vertices.
>
> For a scalar function, you simply get all the vertex values and for a
> vector (or in general tensor-valued) function, you first get all the
> values for component 0, then all values for component 1 etc.
>
> /Anders
>
>
> Alessio Quaglino wrote:
>>> On Tue, Jun 26, 2007 at 02:56:52PM +0200, Alessio Quaglino wrote:
>>>> I'm trying to get my code working with the new dolfin 0.7.0-1 but it
>>>> seems
>>>> there are a several problems. For example, a part of the
>>>> dolfin::Function
>>>> interface has disappeared. In particular, it is not possible to get
>>>> the
>>>> value corresponding to a vertex or the finite element space where the
>>>> function is living. Have these functionalities been moved somewhere
>>>> else?
>>>>
>>>> Regards,
>>>> Alessio Quaglino
>>> Use Function::interpolate() to access the values. Often, one can
>>> avoid ever needing to access the values directly, but if they should
>>> be needed, then it is possible to either interpolate the Function to a
>>> given Cell (getting the expansion coefficients in the local finite
>>> element basis) or get the values at all vertices.
>>>
>>> So, try to avoid accessing the values but if you really need the
>>> values at vertices you can still get them.
>>>
>>> /Anders
>>> _______________________________________________
>>> DOLFIN-dev mailing list
>>> DOLFIN-dev@xxxxxxxxxx
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>>
>> Ok I see, however with interpolate() I can either get all the Vertex
>> values or the values at a given Cell. While the latter case is
>> unefficient
>> for my purpose  because I'd pass through the same Vertex several times,
>> in
>> the former I get a vector with the values at all vertices but no
>> information about how to access such a vector.
>>
>> Regards,
>> Alessio
>>
>>
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>