Direct self-consistent field computations on GPU clusters

We present an implementation of one of the direct self-consistent-field (DSCF) calculation techniques, the restricted Hartree-Fock method, on a high-performance computing cluster outfitted with graphics processing units (GPUs) and demonstrate its effectiveness and scalability up to 128 cluster nodes on molecules of as many as 1,732 atoms. We discuss the overall parallel application architecture that relies on message passing interface for distributing workload among GPU cluster nodes and POSIX threads to manage the use of GPUs internal to each node. This approach of combining coarse and fine-grain parallelism on a distributed memory system allows to perform DSCF calculations on molecules that up until now have been unattainable due to the excessive computational requirements.