data structures like that would be very natural, e.g., in FE codes and similar applications. But I would argue unless there are good solvers that exploits this structure, they are essentially useless. Do such solvers exist? (The only case I know of, off the top of my head, is the trivial case of a higher-order DGFE mass matrix.)
Personally, I would also be quite interested in such data structures and associated sparse solvers. Christoph
