  Parallel implementation features of self-gravitating gas dynamics modeling on
multiple GPUs are considered applying the GPU-Direct technology. The parallel
algorithm for solving of the self-gravitating gas dynamics problem based on
hybrid OpenMP-CUDA parallel programming model has been described in detail. The
gas-dynamic forces are calculated by the modified SPH-method (Smoothed Particle
Hydrodynamics) while the N-body problem gravitational interaction is obtained
by the direct method (so-called Particle-Particle algorithm). The key factor in
the SPH-method performance is creation of the neighbor lists of the particles
which contribute into the gas-dynamic forces calculation. Our implementation is
based on hierarchical grid sorting method using a cascading algorithm for
parallel computations of partial sums at CUDA block. The parallelization
efficiency of the algorithm for various GPUs of the Nvidia Tesla line (K20,
K40, K80) is studied in the framework of galactic' gaseous halos collisions
models by the SPH-method.
