[firedrake] High-contrast Stokes problem

Hi, I would like to solve a Stokes problem with a viscosity which is not constant and could be high in some parts of the domain (as in sinker problem). The solvers that I want to use are in this article: http://dx.doi.org.ezproxy.math.cnrs.fr/10.1016/j.cam.2013.10.016 I would like to use a P0 interpolation for the viscosity function. Could you tell me how can I set this function into my variational formulation ? The other question is to construct the S matrix when you use the Schur complement as a preconditioner. I have to set the pressure mass matrix for S and scale it with the inverse of the viscosity. How can I do that ? Thanks, Loic -- Tel: 01 69 15 60 14 http://www.math.u-psud.fr/~gouarin https://github.com/gouarin