GPU acceleration of an unmodified parallel finite element Navier-Stokes solver

We have previously suggested a minimally invasive approach to include hardware accelerators into an existing large-scale parallel finite element PDE solver toolkit, and implemented it into our software FEAST. Our concept has the important advantage that applications built on top of FEAST benefit from the acceleration immediately, without changes to application code. In this paper we explore the limitations of our approach by accelerating a Navier-Stokes solver. This nonlinear saddle point problem is much more involved than our previous tests, and does not exhibit an equally favourable acceleration potential: Not all computational work is concentrated inside the linear solver. Nonetheless, we are able to achieve speedups of more than a factor of two on a small GPU-enhanced cluster. We conclude with a discussion how our concept can be altered to further improve acceleration.