Design and Implementation of a Parallel Research Kernel for Assessing Dynamic Load-Balancing Capabilities

The Parallel Research Kernels (PRK) are a tool to study parallel architectures and runtime systems from an application perspective. It provides paper and pencil specifications and reference implementations of elementary operations covering a broad range of parallel application patterns. The current PRK are trivially statically load-balanced. Future large-scale systems will require dynamic load balancing for unsteady workloads and for handling system/network fluctuations and non-uniformities. We present a new PRK that requires dynamic load balancing, and provides knobs for controlling workload behavior. It is inspired by Particle-In-Cell (PIC) applications and captures one of the computational patterns in such codes. We give a detailed specification of the new PRK, highlighting the challenges and corresponding design choices that make it compact, arbitrarily scalable and self-verifying. We also present implementations of the PIC PRK in MPI, with and without application-specific load balancing, and show an implementation with runtime-assisted load balancing provided by Adaptive MPI features. Our experimental results provide an illustrative example of how PIC can be used to assess the load-balancing capabilities of modern parallel runtimes.