On Apr 25, 2012, at 7:15 PM, Jed Brown wrote: > On Wed, Apr 25, 2012 at 17:58, Mark F. Adams <mark.adams at columbia.edu> > wrote: > The blocks are not always dense, so by what appears to be your definition of > block size it is not (always) a 'column block size'. But I think that it is > semantically a blocked matrix and hence it has a column block size. > > I think we shouldn't try to encode the near-null space being sparse. For > elasticity, we would only reduce the 18 matrix entries to 12, which is only > about break-even on storage since the dense null space can use fewer column > indices (this is ignoring the dense case also being more efficient).
Its worse than that in aggregation MG, I think, because P is not the null space but Q in a QR decomposition of the rigid body modes ... that might still have some sparsity, not sure. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120425/b57ff6a8/attachment.html>
