Multi-node communication patterns underpin the scalability and parallel performance of the Department of Energy, and broader HPC workloads. Modeling of these patterns is as important aspect of extreme scaled supercomputing systems. To date, many vendors have relied on communication traces which can be difficult to obtain at scale, and take significant I/O storage. For interconnect simulators, the reading and replay of traces requires high-performance I/O subsystems which are often expensive and may be unavailable. To this end, the Ember suite provides communication patterns in a simplified setting (simplified by the removal of application calculations, control flow etc.). This enables more efficient traces to be captured, or in the cases of the Structural Simulation Toolkit (SST, http://sst-simulator.org), these patterns can be easily replicated without tracing using the Ember/SST motif library. The intention of Ember is to enable much larger-scale modeling of high-performance interconnects to achieve DOE's goal of scalable Exascale computing systems. The motifs contained in the suite are intentionally simplified, and by design, do not capture every permutation of the basic patterns within the DOE workload. When used collectively, our experience working with leading industry vendors has been that the motifs capture pertinent aspects of the network interconnect.

Communication Patterns information:

• README.MPI.halo3d (Structured nearest neighbor-like)
• README.MPI.halo3d-26 (Unstructured nearest neighbor-like)
• README.MPI.incast (Multiple inbound messages, I/O-like)
• README.MPI.sweep3d (Communication sweeping)
• README.SHMEM.randominc (Uniform random network access)
• README.SHMEM.hotspotinc (Hotspot random network access)

The Ember Communication Pattern Library is developed by the Scalable Computer Architectures group at Sandia National Laboratories, NM. Funding for the development is provided by the DOE NNSA/ASC Computing Program and the DOE's Exascale Computing Project Hardware Evaluation (HE) team. Information relating to the use of this code can be found in the LICENSE file or individual source code files.

For more information please contact: Simon Hammond (Sandia National Laboratories, sdhammo@sandia.gov).