dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

I've extended the uBlas Krylov solver so that it now works with
matrices of type uBlasKrylovMatrix, only defined by having two
functions size() and mult(). I had to make some minor changes to avoid
using axpy_prod() but the tests I made showed now reduction in
speed. (There is one extra copy of values into a vector compared to
the original code.)

I have temporarily disabled the preconditioning. See all comments

    // FIXME: Preconditioner temporarily disabled

This was necessary since uBlasPreconditioner assumes uBlasSparseMatrix.
We need to make it so that it only assumes uBlasKrylovMatrix. Then we
can have a special subclass, like

    class uBlasILUPreconditioner : public uBlasPreconditioner

or similarly. This class should then take in the constructor as
argument a uBlasSparseMatrix. Then we can overload solve()
uBlasKrylovSolver so we have two versions: one with and one without an
extra preconditioner argument.

I don't think it's possible to let the Krylov solver create a
preconditioner on its own since it only knows how to do mult(), that
is, it only knows that the matrix is uBlasKrylovMatrix. So it can't
create a preconditioner that assumes it can do M.assign(A).

Does that make sense?

/Anders