On Fri, Jan 16, 2009 at 08:20:40AM +0100, Johan Hake wrote:
> Ali!
>
> > def numpyArrayToDolfinMatrix(a):
> > nx = a.shape[0]
> > ny = a.shape[1]
> > m = dolfin.Matrix(nx, ny)
> > m.set(a, numpy.arange(0, nx, dtype=numpy.uint0), numpy.arange(0,
> > ny, dtype=numpy.uint0))
> > m.apply();
> > return m
> >
> > Can you confirm that from the c++ side, just a buffer pointer is
> > passed and there is no loop involved?
>
> For the DOLFIN library this depends on which linear backend you are using.
> This is given by:
>
> dolfin_get("linear algebra backend")
>
> For the uBLAS and MTL4 backend we do a loop. For the PETSc and Epetra backend
> we just send the pointer to the underlying library. The last ones support
> distributed data, which DOLFIN also intend to use, so there will probably be
> some loop in these libraries too.
>
> > I'm actually trying to convert a c++ image data structure to dolfin
> > matrix, why shouldn't dolfin have a design to dynamically accept this
> > sort of input?
>
> Well, the DOLFIN library is built to produce the matrices by assembling
> variational problems defined by forms. The DOLFIN linear algebra part is
> built to facilitate this, and to be able to use different backends.It sounds like you should consider using a dense matrix representation which means using the class uBLASDenseMatrix. -- Anders > > Here is how the c++ image data is converted from/to > > numpy in our project: > > > > http://code.google.com/p/wrapitk/source/browse/trunk/ExternalProjects/PyBuf > >fer/itkPyBuffer.txx > > > > I'm trying to solve some variational image processing problems where > > the data term in the PDE comes from the image buffer. Just to make > > sure, is dolfin matrix the right way of inputing the image data or am > > I missing something? > > I think the best way to find out is to state your question in mathematical > terms. Who knows maybee someone on the list are trying to solve the same > problem, I am not... > > Probably you want to read in the data in a Function and use this in your > variational formulation. > > Johan > _______________________________________________ > DOLFIN-dev mailing list > [email protected] > http://www.fenics.org/mailman/listinfo/dolfin-dev
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