A Parallel Adaptive P3M code with Hierarchical Particle Reordering

We discuss the design and implementation of HYDRA_OMP a parallel implementation of the Smoothed Particle Hydrodynamics-Adaptive P3M (SPH-AP3M) code HYDRA. The code is designed primarily for conducting cosmological hydrodynamic simulations and is written in Fortran77+OpenMP. A number of optimizations for RISC processors and SMP-NUMA architectures have been implemented, the most important optimization being hierarchical reordering of particles within chaining cells, which greatly improves data locality thereby removing the cache misses typically associated with linked lists. Parallel scaling is good, with a minimum parallel scaling of 73% achieved on 32 nodes for a variety of modern SMP architectures. We give performance data in terms of the number of particle updates per second, which is a more useful performance metric than raw MFlops. A basic version of the code will be made available to the community in the near future.Comment: 34 pages, 12 figures, accepted for publication in Computer Physics Communication

Properties of the simulated agn activity function in isolated galaxy mergers

xv, 122 leaves : ill. (chiefly col.) ; 29 cm.Includes abstract.Includes bibliographical references (leaves 109-122).Numerical modeling of active galactic nuclei (AGN) poses many challenges, from uncertainties about the underlying physics to dynamic range issues. We present a study of simulated activity functions (AF; the differential of the amount of time spent by a black hole above a given Eddington ratio) in simulations of mergers of Milky-Way like galaxy models using seven different BH feedback algorithms, accretion algorithms, and initial conditions. When considered over the entire simulation the simulated AFs are more dominant at high Eddington ratios than observationally (Schechter-type) inferred AFs. However, during passive evolutionary stages there is considerably closer agreement with observational results. We also demonstrate that two separate algorithms produce AFs which are approximately mass invariant, in agreement with observations. Lastly, we show that numerical uncertainties in AFs and other properties of the remnant such as black hole mass, star formation rates, and accretion rates, are well below a factor of two