mitchell_05, Mitchell's "battery" problem. This problem is defined on a rectangle which has been subdivided into seven subregions, and various coefficient functions are piecewise constant over each subregion.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
The DEAL.II implementations of these problems was done by Lukas Bystricky, of the Department of Scientific Computing, Florida State University.