On Wed, Apr 25, 2012 at 17:58, Mark F. Adams <mark.adams@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).