Before revision:  Convenience for the user and efficiency is demonstrated on the example of accelerating a large-scale Stokes problemsolution with a Schur pressure correction preconditioner. The user may select algorithmic components of the solver by adjusting template parameters without any change to the codebase.
After revision:  Convenience for the user and efficiency is demonstrated on the example of accelerating an iterative solver of a discontinuous Galerkin finite element method for the Stokes problem. The implementation allows selecting algorithmic components of the solver by adjusting template parameters without any change to the codebase.