Hydra: A 3-D parallel discrete ordinates code for massive transport calculation

Hydra is a three-dimensional parallel discrete ordinatcs code for radiation shielding calculation and reactor physics analysis. Hydra uses the state-of-the-art spatial discretization techniques to obtain accurate solutions to the linear Boltzmann transport equation. Both source iteration and Krylov methods have been implemented to solve the within-group equations. The mesh-corner DSA with red-black sweep preconditioned Conjugate Gradient method has been used to accelerate the source iteration. The Koch-Baker-Alcouffe (KBA) algorithm has been applied to perform the spatial domain decomposition. In order to improve the scalability of KBA algorithm, two kinds of multi-angular sweep strategies have been developed: the four-octant sweep (FOS) and the diagonal-octant sweep (DOS). Verification for Hydra has been done by lots of benchmarks. In this paper, Hydra's solutions to VENUS- 2 and HBR-2 arc in excellent agreement with the ones from TORT. Weak scaling efficiency tests have been performed on the Tianhe-2 super computer by using 10²to 10⁴processors. For the test using 10⁴processors, the weak scaling efficiency is improved by over 10 percent (DOS) and 13 percent (FOS) compared to the standard KBA algorithm, respectively.