  We present recent updates and improvements of the graphical processing unit
(GPU) N-body code GENGA. Modern state-of-the-art simulations of planet
formation require the use of a very high number of particles to accurately
resolve planetary growth and to quantify the effect of dynamical friction. At
present the practical upper limit is in the range of 30,000 - 60,000 fully
interactive particles; possibly a little more on the latest GPU devices. While
the original hybrid symplectic integration method has difficulties to scale up
to these numbers, we have improved the integration method by i) introducing
higher level changeover functions and ii) code improvements to better use the
most recent GPU hardware efficiently for such large simulations. We added
treatments of non-Newtonian forces such as general relativity, tidal
interaction, rotational deformation, the Yarkovsky effect, and
Poynting-Robertson drag, as well as a new model to treat virtual collisions of
small bodies in the solar system. We added new tools to GENGA, such as
semi-active test particles that feel more massive bodies but not each other, a
more accurate collision handling and a real-time openGL visualization. We
present example simulations, including a 1.5 billion year terrestrial planet
formation simulation that initially started with 65,536 particles, a 3.5
billion year simulation without gas giants starting with 32,768 particles, the
evolution of asteroid fragments in the solar system, and the planetesimal
accretion of a growing Jupiter simulation. GENGA runs on modern NVIDIA and AMD
GPUs.
