On Sun, Dec 16, 2007 at 12:52:38PM +0100, Ola Skavhaug wrote: > Anders Logg skrev den 16/12-2007 følgende: > > On Sun, Dec 16, 2007 at 09:46:56AM +0000, Garth N. Wells wrote: > > > > > > > > > Gideon Simpson wrote: > > > > I'm interested in implementing the Elman et al. preconditioner for > > > > Stokes in the fenics suite. This involves building an approximate > > > > schur > > > > complement for the block strucutre matrix > > > > A B^T > > > > B 0 > > > > representing the weak form of the stokes operator. has anyone > > > > experimented, if not with this sort, some sort of block structure using > > > > the fenics front end? > > > > > > > > > > > > > > No, when using the default uBLAS backend, there aren't any sophisticated > > > preconditioners. You can create a preconditioner which derives from > > > uBLASPreconditioner. > > > > > > You can also look at using PETSc which provides a variety of > > > preconditioners. > > > > > > Garth > > > > Since this is quite common, maybe we should consider adding a some > > abstractions for block systems/preconditioners: BlockMatrix, > > BlockPreconditioner? > > > > PyCC has something like this (but only in Python) that we can look at. > > Ola knows more about it. > > It would be quite simple to port the block matrices in PyCC to C++. It will > be placed a bit down on my todo list, however. > > We have two types of block-matrices: > > BlockMatrix > DiagBlockMatrix > > Additionally, we have a zero-matrix, since block systems often contain zeros, > and we want to make sure the matrix dimensions in the block system are > correct. > > Ola
ok, let's try to get this going at some point (but my todo-list is also expanding). -- Anders _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
