João Vicente Ferreira Lima

The demand for computing power, along with the diversity of computational problems, culminated in a variety of heterogeneous architectures. Among them, hybrid architectures combine different specialized hardware into a single chip, comprising a System-on-Chip (SoC). Since these architectures usually have limited resources, efficiently splitting data and tasks between the different hardware is primal to improve performance. In this context, we explore the non-uniform decomposition of the data domain to improve fluid flow simulation performance on heterogeneous architectures. We evaluate two hybrid architectures: one comprised of a general-purpose x86 CPU and a graphics processing unit (GPU) integrated into a single chip (AMD Kaveri SoC), and another comprised by a general-purpose ARM CPU and a Field Programmable Gate Array (FPGA) integrated into the same chip (Intel Arria 10 SoC). We investigate the effects on performance and energy efficiency of data decomposition on each platform’s devices on a collaborative execution. Our case study is the well-known Lattice Boltzmann Method (LBM), where we apply the technique and analyze the performance and energy efficiency of five kernels on both devices on each platform. Our experimental results show that non-uniform partitioning improves the performance of LBM kernels by up to 11.40% and 15.15% on AMD Kaveri and Intel Arria 10, respectively. While AMD’s Kaveri platform’s performance efficiency is of up to 10.809 MLUPS with an energy efficiency of 142.881 MLUPKJ, Intel’s Arria 10 platform’s is of up to 1.12 MLUPS and 82.272 MLUPKJ.

Most recent HPC platforms have heterogeneous nodes composed of multi-core CPUs and accelerators, like GPUs. Programming such nodes is typically based on a combination of OpenMP and CUDA/OpenCL codes; scheduling relies on a static partitioning and cost model. We present the XKaapi runtime system for data-flow task programming on multi-CPU and multi-GPU architectures, which supports a data-flow task model and a locality-aware work stealing scheduler. XKaapi enables task multi-implementation on CPU or GPU and multi-level parallelism with different grain sizes. We show performance results on two dense linear algebra kernels, matrix product (GEMM) and Cholesky factorization (POTRF), to evaluate XKaapi on a heterogeneous architecture composed of two hexa-core CPUs and eight NVIDIA Fermi GPUs. Our conclusion is two-fold. First, fine grained parallelism and online scheduling achieve performance results as good as static strategies, and in most cases outperform them. This is due to an improved work stealing strategy that includes locality information; a very light implementation of the tasks in XKaapi; and an optimized search for ready tasks. Next, the multi-level parallelism on multiple CPUs and GPUs enabled by XKaapi led to a highly efficient Cholesky factorization. Using eight NVIDIA Fermi GPUs and four CPUs, we measure up to 2.43 TFlop/s on double precision matrix product and 1.79 TFlop/s on Cholesky factorization; and respectively 5.09 TFlop/s and 3.92 TFlop/s in single precision.

The constant growth of social media, unconventional web technologies, mobile applications, and Internet of Things (IoT) devices create challenges for cloud data systems in order to support huge datasets and very high request rates. NoSQL databases, such as Cassandra and HBase, and relational SQL databases with replication, such as Citus/PostgreSQL, have been used to increase horizontal scalability and high availability of data store systems. In this paper, we evaluated three distributed databases on a low-power low-cost cluster of commodity Single-Board Computers (SBC): relational Citus/PostgreSQL and NoSQL databases Cassandra and HBase. The cluster has 15 Raspberry Pi 3 nodes with Docker Swarm orchestration tool for service deployment and ingress load balancing over SBCs. We believe that a low-cost SBC cluster can support cloud serving goals such as scale-out, elasticity, and high availability. Experimental results clearly demonstrated that there is a trade-off between performance and replication, which provides availability and partition tolerance. Besides, both properties are essential in the context of distributed systems with low-power boards. Cassandra attained better results with its consistency levels specified by the client. Both Citus and HBase enable consistency but it penalizes performance as the number of replicas increases.