dolfin team mailing list archive

[A Navaei <axnavaei@xxxxxxxxxxxxxx>]

2009/2/25  <kent-and@xxxxxxxxx>:
>> I'm not sure if I'm making sense here. Both of you suggested using
>> assemble which requires Form which, if I'm not wrong, requires
>> Function and that needs FunctionSpace which requires Mesh, but I
>> emphasised that this is no FEM problem :) I'm just trying to get the
>> best of available LA in dolfin.
>>
>> Let me give you a concrete example, have a look at Eq 12 of this paper:
>>
>> http://www.mia.uni-saarland.de/Publications/brox-eccv04-of.pdf
>>
>> Is it possible to use assemble() to extract A and b out of this
>> equation? Many of the coefficients in the equation are image data, I
>> guess I should convert the image data to Matrix and use Variable for
>> the unknowns?
>
> In Dolfin we use FEM. The assemble function turns a variational form
> into a matrix, a vector or a number depending on the form.

Correct, however, due to the rich linear algebra backends in dolfin,
it also comes with other features, such as ODE solvers. It would be
nice to use the existing automation for other approaches as well.


-Ali

>
> Kent
>
>>
>>
>> -Ali
>>
>> 2009/2/25  <kent-and@xxxxxxxxx>:
>>>
>>> I'm not exactly sure what you are asking. But it is easy to obtain the
>>> matrices
>>> and vectors in the linear system to be solved.
>>>
>>> eg.
>>> dolfin/demo/la/trilinos/python/demo.py
>>>
>>> shows how to solve the system using Trilinos. You can use dolfin
>>> to make matrices and vectors in PETSc, uBlas, MTL, and Trilinos format.
>>> You can choose to let dolfin solve it for you or you can get the
>>> underlying
>>> matrix and solve it with the above LA libraries.
>>>
>>> Kent
>>>
>>>
>>>
>>>> Is the linear algebra support in dolfin capable of automatically
>>>> generating the sparse linear system of equations? (I know that ffc
>>>> effectively does this, but note that this question does not involve
>>>> solving a PDE using FEM, but a linear system of equations).
>>>>
>>>> For example, assume we have some busy sets of linear equations and we
>>>> wish to convert them to Ax = b so that we can feed them to the linear
>>>> solvers. Is there any way of automatically obtaining A and b avoiding
>>>> manual calculations and hard-coding?
>>>>
>>>>
>>>> -Ali
>>>> _______________________________________________
>>>> DOLFIN-dev mailing list
>>>> DOLFIN-dev@xxxxxxxxxx
>>>> http://www.fenics.org/mailman/listinfo/dolfin-dev
>>>>
>>>
>>>
>>>
>>
>
>
>