dolfin team mailing list archive

[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.

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
>>>
>>
>>
>>
>