Dear libMesh team,

As far as I see, there seems not to be any interface in libMesh to 
solve a system in a matrix free way.

I have to solve a linear system whose matrix basically has the 
following structure:

A = B + v*w^T

where B is a sparse matrix and v and w are vectors, so that v*w^T is a 
full matrix.  Obviously, it is not advisable to store the full matrix. 
Instead, I would like to store B, v, and w, and then supply a method 
to multiply the matrix with a given vector (which is obviously quite 
easy, even in parallel).

What whould be the things to do?  I guess, first I have to find out 
PETSc's API for matrix free solving (provided that such a thing 
exists, but I think it does).  Then, I can either use PETSc directly 
or -- presumably better -- extend the API of your LinearSolver class 
towards matrix free solving.  Of course, the latter would require to 
do something for the other solver packages as well (Laspack etc.), but 
I would just call libmesh_not_implemented() there.

Would such an API extension be welcome?  Do you have any different 
ideas or suggestions?

Best Regards,

Tim

-- 
Dr. Tim Kroeger                                        Phone +49-421-218-7710
[EMAIL PROTECTED], [EMAIL PROTECTED]  Fax   +49-421-218-4236

MeVis Research GmbH, Universitaetsallee 29, 28359 Bremen, Germany

Amtsgericht Bremen HRB 16222
Geschaeftsfuehrer: Prof. Dr. H.-O. Peitgen

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