dolfin team mailing list archive

["Garth N. Wells" <g.n.wells@xxxxxxxxxx>]

Anders Logg wrote:
> Some more inconsistencies in the linear algebra interface:
>
> 1. In GenericVector, there's an operator() but not in GenericMatrix.
> Should we add one to GenericMatrix?

This is used in applying Dirichlet boundary conditions. Rather than 
adding operator() to GenericMatrix, I would consider removing it from 
GenericVector (and making some changes in the class FEM for applying 
Dirichlet boundary conditions).


> 2. Should we make it assignable? This would require the
> GenericMatrix::Element trick. Maybe it's ok since this is just a fix
> for the C++ interface? Indexing in the Python interface is handled
> differently anyway.
>
> 3. Are all the functions in GenericMatrix/Vector necessary? Could some
> be removed? 

At a glance, I'd say that they are all necessary for assmebly.

Also, there are plenty of functions in PETScMatrix/Vector
> and uBlasMatrix/Vector that are not in GenericMatrix/Vector. Should we
> make sure that the interface stays the same for all linear algebra
> types so for example only GenericMatrix functions are present in the
> public interface of PETScMatrix?

It could be expanded (particularly GenericVector), but I would still try 
to keep it compact. Some basic algebra operations would be good (+, +=, 
-, -=, *=). They are used at least in src/modules/elasticity.

Ideally, if a Matrix/Vector is created all the members functions which 
are called should be in GenericMatrix/Vector, and if specialised 
functions are required, a PETScMatrix/Vector or uBlasMatrix/Vector 
should be created. Is it possible somehow to "hide" member functions of 
PETScMatrix/uBlasMatrix which are not in GenericMatrix/Vector when using 
a Matrix/Vector?

Garth

> 4. Indexing in a PETSc matrix does not work as expected:
>
>   >>> from dolfin import *
>   >>> A = Matrix(10, 10)
>   >>> print A[(5,5)]
>   [0]PETSC ERROR: MatGetValues() line 1324 in src/mat/interface/matrix.c
>   [0]PETSC ERROR: Object is in wrong state!
>   [0]PETSC ERROR: Not for unassembled matrix!
>   1.27319747458e-313
>
> The natural would be for this to return zero.
>
> /Anders
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