On Feb 8, 2011, at 7:28 AM, Umut Tabak wrote:
> Dear all,
>
> I would like to create an operator matrix like
>
> (I - 0.5 C^{-1}(C+kD))
>
> for linear iterative solvers, where k is a given scalar and C and D are
> matrices from a FE discretization.
>
> Moreover, the second part of the operator matrix can be constructed
> efficiently by using a matrix-vector product and a forward-backward
> substitution since I have the factorization of C which is a symmetric matrix.
>
> I guess I should use matrix free operations and create the two matrices as
> shell matrices such as M1 (for I) and M2 (for the rest of above) and sum
> them, is this the most efficient way to do this?
>
I would make a single MATSHELL, inside it I would store the k, the matrix C
and the matrix D, in addition I would store in it a KSP object where I have
called KSPSetOperators() with the C matrix. Then the PCApply for the shell
matrix could be .5*( I - k* kspsolve(C)*D) if I have my math correct. No
reason that I can see for having more than one shell matrix.
Barry
> Best wishes,
> Umut
>
> --
> - Hope is a good thing, maybe the best of things
> and no good thing ever dies...
> The Shawshank Redemption, replique of Tim Robbins
>
