Presto is an open source distributed query engine that supports much of the SQL analytics workload at Facebook. Presto is designed to be adaptive, flexible, and extensible. It supports a wide variety of use cases with diverse characteristics. These range from user-facing reporting applications with sub-second latency requirements to multi-hour ETL jobs that aggregate or join terabytes of data. Presto's Connector API allows plugins to provide a high performance I/O interface to dozens of data sources, including Hadoop data warehouses, RDBMSs, NoSQL systems, and stream processing systems. In this paper, we outline a selection of use cases that Presto supports at Facebook. We then describe its architecture and implementation, and call out features and performance optimizations that enable it to support these use cases. Finally, we present performance results that demonstrate the impact of our main design decisions.

Simulation-Based Design (SBD) approaches can help conceptualize engineering plans and design activities with the adoption of Virtual / Augmented Reality based digital mockup techniques and technologies. This paper outlines preliminary activities based on SBD principles aimed at supporting some of the material transport activities for NASA's Lunar Mission. Immersive Virtual Reality (VR) based simulation environments were created to support some of the simulation based design activities. The engineering design activities included (i) planning and conceptualizing an autonomous system for transporting payloads from the Gateway to the Lunar surface, (ii) exploring design of cable-based robotic system for transporting parts from one location to another on the surface of the Moon and (iii) studying path planning approaches to transport materials on the Lunar surface. The initial conceptualization of design ideas for these three thrusts are presented along with a discussion of the SBD implementation using the Unity engine on the immersive Vive platform.

We show that finding a subgraph realization with the minimum generalized Randić index for a given base graph and degree sequence is solvable in polynomial time by formulating the problem as the minimum weight perfect b-matching problem of Edmonds (J Res Natl Bur Stand 69B (1965), 125–130). However, the realization found via this reduction is not guaranteed to be connected. Approximating the minimum weight perfect b-matching problem subject to a connectivity constraint is shown to be NP-hard. For instances in which the optimal solution to the minimum Randić index problem is not connected, we describe a heuristic to connect the graph using pairwise edge exchanges that preserves the degree sequence. Although we focus on finding graph realizations with minimum Randić index, our results extend to finding graph realizations with maximum Randić index as well. Applications of the Randić index are provided to synchronization of neuronal networks controlling respiration in mammals and to normalizing cortical thickness networks in diagnosing individuals with dementia. © 2016 Wiley Periodicals, Inc. NETWORKS, Vol. 67(4), 338–347 2016