A novel hybrid CPU-GPU generalized eigensolver for electronic structure calculations based on fine grained memory aware tasks

The adoption of hybrid GPU-CPU nodes in traditional supercomputing platforms such as the Cray-XK6 opens acceleration opportunities for electronic structure calculations in materials science and chemistry applications, where medium-sized generalized eigenvalue problems must be solved many times. These eigenvalue problems are too small to effectively solve on distributed systems, but can benefit from the massive compute performance concentrated on a single node, hybrid GPU-CPU system. However, hybrid systems call for the development of new algorithms that efficiently exploit heterogeneity and massive parallelism of not just GPUs, but of multi/many-core CPUs as well. Addressing these demands, we developed a novel algorithm featuring innovative: Fine grained memory aware tasks, Hybrid execution/scheduling, and Increased computational intensity}. The resulting eigensolvers are state-of - The-art in HPC, significantly outperforming existing libraries. We describe the algorithm and analyze its performance impact on applications of interest when different fractions of eigenvectors are needed by the host electronic structure code.