  We present a two-dimensional Cartesian code based on high order discontinuous
Galerkin methods, implemented to run in parallel over multiple GPUs. A simple
planet-disc setup is used to compare the behaviour of our code against the
behaviour found using the FARGO3D code with a polar mesh. We make use of the
time dependence of the torque exerted by the disc on the planet as a mean to
quantify the numerical viscosity of the code. We find that the numerical
viscosity of the Keplerian flow can be as low as a few $10^{-8}r^2\Omega$, $r$
and $\Omega$ being respectively the local orbital radius and frequency, for
fifth order schemes and resolution of $\sim 10^{-2}r$. Although for a single
disc problem a solution of low numerical viscosity can be obtained at lower
computational cost with FARGO3D (which is nearly an order of magnitude faster
than a fifth order method), discontinuous Galerkin methods appear promising to
obtain solutions of low numerical viscosity in more complex situations where
the flow cannot be captured on a polar or spherical mesh concentric with the
disc.
