dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Wed, Feb 25, 2009 at 11:10:17PM +0000, A Navaei wrote:
> 2009/2/25 Anders Logg <logg@xxxxxxxxx>:
> > On Wed, Feb 25, 2009 at 09:34:44PM +0000, A Navaei wrote:
> >> 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?
> >
> > Yes! Isn't that what you are using already? Define a bilinear form a,
> > a linear form L, and then just assemble the matrix and vector by
> >
> >  A = assemble(a)
> >  b = assemble(L)
> 
> Are the bilinear and linear forms, which you referred to, supposed to
> be mesh-less? (Can we create a mesh-less Form?)

No, you need a mesh.

> Also, I was not able to find the above assemble(), the closest is
> Assembler::assemble (GenericTensor &A, const Form &a).

The above was in Python. In C++ you need to do

  assemble(A, a);
  assemble(b, L);

-- 
Anders



> 
> -Ali
> 
> >
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