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 > -- > Anders > _______________________________________________ > DOLFIN-dev mailing list > [email protected] > http://www.fenics.org/mailman/listinfo/dolfin-dev _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
