A High-Performance Design, Implementation, Deployment, and Evaluation of The Slim Fly Network

Novel low-diameter network topologies such as Slim Fly (SF) offer significant cost and power advantages over the established Fat Tree, Clos, or Dragonfly. To spearhead the adoption of low-diameter networks, we design, implement, deploy, and evaluate the first real-world SF installation. We focus on deployment, management, and operational aspects of our test cluster with 200 servers and carefully analyze performance. We demonstrate techniques for simple cabling and cabling validation as well as a novel high-performance routing architecture for InfiniBand-based low-diameter topologies. Our real-world benchmarks show SF's strong performance for many modern workloads such as deep neural network training, graph analytics, or linear algebra kernels. SF outperforms non-blocking Fat Trees in scalability while offering comparable or better performance and lower cost for large network sizes. Our work can facilitate deploying SF while the associated (open-source) routing architecture is fully portable and applicable to accelerate any low-diameter interconnect

Assessing the nutritional content and adequacy of food parcels among vulnerable Lebanese during a double crisis: COVID-19 pandemic and an economic meltdown

Abstract Objectives: This study aimed to explore the nutritional content and quality of food parcels distributed in Lebanon and assess their adherence to dietary guidelines during the COVID-19 pandemic and an unprecedented economic crisis. Design: Cross-sectional study (June–July 2020); phone survey (thirty items). Setting: Lebanon. Participants: Food parcel providers (FPP; n 72) involved in food parcel distribution (FPD), mainly to Lebanese households. Results: FPP included international non-governmental organizations (INGO) (n 3), local non-governmental organizations (n 45) and personal initiatives (n 24). Overall, low adherence to the World Food Programme (WFP) food parcel guidelines were observed among FPP for specific food items, including vegetables, fish, legumes and cereals, whereas salt content significantly surpassed the guidelines (all P-values <0·001). On average, a food parcel provided 608·4 ± 55 kcal/d/person. The greatest contributors to total energy intake (TE) in the food parcel were carbohydrates (46·4 %) and fats (46·8 %), while protein contributed to 7 %TE. In addition, %TE from fats and sugars significantly surpassed the dietary reference intakes (DRI) for a single person per d (134–234 % and 185 % of DRI, respectively, P-values <0·001). Only 10–15 % of daily needs for key micronutrients, including Fe, Zn, thiamin, riboflavin and dietary folate, were met through the food parcels. Adequate food safety and hygiene practices were reported among FPP, yet dramatic changes in food costs due to overlapping crises affected the quality and quantity of food in parcels. Conclusions: Findings highlight the need to improve the nutritional content of food parcels and adherence to dietary guidelines to alleviate food and nutrition insecurity while preventing diet-related diseases among vulnerable beneficiaries in Lebanon

Parallel I/O and the metadata wall

Large HPC installations typically make use of parallel file systems that adhere to POSIX I/O conventions, and that implement a separation of data and metadata in order to maintain high performance. File systems such as GPFS and Lustre have evolved to enable an increase in data bandwidth that is primarily achieved by adding more disk drives behind an increasing number of disk controllers. Improvements in metadata performance cannot be achieved by just deploying a large volume of hardware, as the defining characteristics are the number of simultaneous operations that can be carried out and the latency of those operations. For highly scalable applications using parallel I/O libraries, the speed of metadata operations, such as opening a file on thousands of processes, has the potential to become the major bottleneck to improved I/O performance. This Metadata Wall has the ability to grow such that metadata operations can take much longer than the subsequent data operations, even on systems with very large amounts of I/O data bandwidth. We present results showing the performance of metadata operations with standard disk equipment and with solid state storage hardware, and extrapolate whether we expect the evolution in hardware alone will be sufficient to limit the effects of this I/O Metadata Wall. We also report challenges in making the metadata I/O measurements and subsequent analysis for parallel file systems