In hydrocarbon reservoir simulation the governing partial differential equations consist of parabolic and hyperbolic equations. The resulting linear systems are solved by GMRES preconditioned by the CPR preconditioner. The main step in the CPR preconditioner is the approximation of the parabolic pressure field. In the studied commercial reservoir simulator the pressure field is approximated by one V-cycle of classical AMG with standard coarsening. However, for many real life test cases the strong scalability of the AMG solution method is poor.
In this talk we investigate alternatives to classical AMG with standard coarsening by applying more aggressive coarsening techniques. We compare SAMG for various large scale simulation runs. Due to the aggressive coarsening the algebraic and geometric complexity becomes lower but at the expense of slower convergence and an increase in total simulation time. We will discuss the numerical results and propose strategies how to further improve the strong scalability by more advanced (aggressive) coarsening techniques.