You may have seen this already: Garth has published some code using PETSc FieldSplit preconditioners for block preconditioning of Stokes-like problems with DOLFIN (C++ interface only) [1]. This is code for magma dynamics problems from a paper by Sander Rhebergen, Garth et. al which is published on arXiv [2]. You should join the FEniCS community on G+ [3] if you haven't already. Florian [1]: https://bitbucket.org/magma-dynamics/preconditioning [2]: http://arxiv.org/abs/1311.6372 [3]: https://plus.google.com/u/0/communities/105550716956576029273