On the Greenness of In-Situ and Post-Processing Visualization Pipelines

Post-processing visualization pipelines are traditionally used to gain insight from simulation data. However, changes to the system architecture for high-performance computing (HPC), dictated by the exascale goal, have limited the applicability of post-processing visualization. As an alternative, in-situ pipelines are proposed in order to enhance the knowledge discovery process via "real-time" visualization. Quantitative studies have already shown how in-situ visualization can improve performance and reduce storage needs at the cost of scientific exploration capabilities. However, to fully understand the trade-off space, a head-to-head comparison of power and energy (between the two types of visualization pipelines) is necessary. Thus, in this work, we study the greenness (i.e., Power, energy, and energy efficiency) of the in-situ and the post-processing visualization pipelines, using a proxy heat-transfer simulation as an example. For a realistic I/O load, the in-situ pipeline consumes 43% less energy than the post-processing pipeline. Contrary to expectations, our findings also show that only 9% of the total energy is saved by reducing off-chip data movement, while the rest of the savings comes from reducing the system idle time. This suggests an alternative set of optimization techniques for reducing the power consumption of the traditional post-processing pipeline.