> On Nov 12, 2014, at 7:49 PM, Jed Brown <[email protected]> wrote: > > Barry Smith <[email protected]> writes: >> Perhaps we need a generic way of attaching null spaces to parts of >> matrices and to parts of matrices in different basis (which is what >> a Schur complement is). So (and this is likely overly simplistic) >> one could supply a null space, an index set, and a flag indicating >> either "part of the matrix" or the "Schur complement of the matrix >> with respect to an index set". These provided null spaces could >> then be used by the preconditioners (like Fieldsplit) that >> manipulate parts of the matrix or Schur complement. > > Yes, this is conceptually right, but it looks to me like it gets hairy > for recursive splitting.
Indeed it could. Perhaps we could start by unifying the concept of a sub matrix and a Schur complement of the same part of the matrix? I'm not sure how to do that. Barry
