  Computational fluid dynamics is a crucial tool to theoretically explore the
cosmos. In the last decade, we have seen a substantial methodological
diversification with a number of cross-fertilizations between originally
different methods. Here we focus on recent developments related to the Smoothed
Particle Hydrodynamics (SPH) method. We briefly summarize recent technical
improvements in the SPH-approach itself, including smoothing kernels, gradient
calculations and dissipation steering. These elements have been implemented in
the Newtonian high-accuracy SPH code MAGMA2 and we demonstrate its performance
in a number of challenging benchmark tests. Taking it one step further, we have
used these new ingredients also in the first particle-based,
general-relativistic fluid dynamics code that solves the full set of Einstein
equations, SPHINCS_BSSN. We present the basic ideas and equations and
demonstrate the code performance at examples of relativistic neutron stars that
are evolved self-consistently together with the spacetime.
