Will Usher, Ingo Wald, Aaron Knoll, Michael Papka and Valerio Pascucci
We present a system for interactive in situ visualization of large particle simulations, suitable for general CPU-based HPC architectures. As simulations grow in scale, in situ methods are needed to alleviate IO bottlenecks and visualize data at full spatio-temporal resolution. We use a lightweight loosely-coupled layer serving distributed data from the simulation to a data-parallel renderer running in separate processes. Leveraging the OSPRay ray tracing framework for visualization and balanced P-k-d trees, we can render simulation data in real-time, as they arrive, with negligible memory overhead. This flexible solution allows users to perform exploratory in situ visualization on the same computational resources as the simulation code, on dedicated visualization clusters or remote workstations, via a standalone rendering client that can be connected or disconnected as needed. We perform proof of concept evaluation on Stampede with a simulation in Uintah on up to 55M particles, and show that our approach provides many of the advantages of tightly-coupled systems, with the flexibility to render on a wide variety of remote and coprocessing resources.