Aerospace systems are increasingly dependent upon software for their functionality, with associated software spanning a wide range of application domains. These include aircraft and spacecraft flight controls, mission...
详细信息
Aerospace systems are increasingly dependent upon software for their functionality, with associated software spanning a wide range of application domains. These include aircraft and spacecraft flight controls, mission computing, weapons management, command and control, surveillance, sensor management and processing, telemetry, and more. Understanding of their unique challenges has driven technology development on many fronts associated both with the products-such as real-time component-based application frameworks, supporting middleware, and algorithms-and the processes and tools by which they are created-such as model-based development and integration, automated code generation, simulations, and desktop test environments. This paper describes a number of these domains and challenges, future directions associated with networking and systems of systems, and technologies facilitating their development within The Boeing Company.
In a distributed environment, CPU speed is only one factor-and not necessarily the most important - in determining time an application needs to complete its tasks. In some applications, the dominant factor may instead...
详细信息
In a distributed environment, CPU speed is only one factor-and not necessarily the most important - in determining time an application needs to complete its tasks. In some applications, the dominant factor may instead be communication. Most existing benchmark suites measure just the computational performance of a given workstation or the maximum network throughput under ideal conditions. The authors have : developed the BTU (bits to the user) benchmark to take into account both concurrent activities within a workstation (such as CPU and I/O processes that compete for resources) and concurrent activities on the network. BTU can be used to more realistically assess a workstation's communication performance under a particular load. It provides detailed reports to evaluate hardware and software configurations and identify their communication bottlenecks. The BTU benchmark produces results at various levels of abstraction - from a single number that characterizes average;performance to a report of how all the individual test suite : components performed.
Suppose in a graph G vertices can be either red or blue. Let k be odd. At each time step, each vertex v in G polls k random neighbours and takes the majority colour. If it does not have k neighbours, it simply polls a...
详细信息
Suppose in a graph G vertices can be either red or blue. Let k be odd. At each time step, each vertex v in G polls k random neighbours and takes the majority colour. If it does not have k neighbours, it simply polls all of them, or all less one if the degree of v is even. We study this protocol on graphs of a given degree sequence, in the following setting: initially each vertex of G is red independently with probability alpha < 1/2, and is otherwise blue. We show that if a is sufficiently biased, then with high probability consensus is reached on the initial global majority within O(log(k) log(k) n) steps if 5 <= k <= d, and O(log(d) log(d) n) steps if k > d. Here, d >= 5 is the effective minimum degree, the smallest integer which occurs Theta(n) times in the degree sequence. We further show that on such graphs, any local protocol in which a vertex does not change colour if all its neighbours have that same colour, takes time at least Omega (log(d) log(d) n), with high probability. Additionally, we demonstrate how the technique for the above sparse graphs can be applied in a straightforward manner to get bounds for the Erdos-Renyi random graphs in the connected regime. (C) 2014 Elsevier B.V. All rights reserved.
AbstractSINA is an object‐oriented language for distributed and concurrent programming. The primary focus of this paper is on the object‐oriented concurrent programming mechanisms of SINA and their implementation. T...
详细信息
AbstractSINA is an object‐oriented language for distributed and concurrent programming. The primary focus of this paper is on the object‐oriented concurrent programming mechanisms of SINA and their implementation. This paper presents the SINA constructs for concurrent programming and inter‐object communication, some illustrative examples and a message‐based implementation model for SINA that we have used in our current impleme
Due to sparse charging infrastructure and short driving ranges, drivers of battery electric vehicles (BEVs) can experience range anxiety, which is the fear of stranding with an empty battery. To help eliminate range a...
详细信息
Due to sparse charging infrastructure and short driving ranges, drivers of battery electric vehicles (BEVs) can experience range anxiety, which is the fear of stranding with an empty battery. To help eliminate range anxiety and make BEVs more attractive for customers, accurate range estimation methods need to be developed. In recent years, many publications have suggested machine learning algorithms as a fitting method to achieve accurate range estimations. However, these algorithms use a large amount of data and have high computational requirements. A traditional placement of the software within a vehicle's electronic control unit could lead to high latencies and thus detrimental to user experience. But since modern vehicles are connected to a backend, where software modules can be implemented, high latencies can be prevented with intelligent distribution of the algorithm parts. On the other hand, communication between vehicle and backend can be slow or expensive. In this article, an intelligent deployment of a range estimation software based on ML is analyzed. We model hardware and software to enable performance evaluation in early stages of the development process. Based on simulations, different system architectures and module placements are then analyzed in terms of latency, network usage, energy usage, and cost. We show that a distributed system with cloud-based module placement reduces the end-to-end latency significantly, when compared with a traditional vehicle-based placement. Furthermore, we show that network usage is significantly reduced. This intelligent system enables the application of complex, but accurate range estimation with low latencies, resulting in an improved user experience, which enhances the practicality and acceptance of BEVs.
We present a unified model to compute various performance measures when Poissonian and non-Poissonian (renewal) multi-slot traffic streams are offered to a digital link in a (double) loss system. We represent the non-...
详细信息
We present a unified model to compute various performance measures when Poissonian and non-Poissonian (renewal) multi-slot traffic streams are offered to a digital link in a (double) loss system. We represent the non-Poissonian arrival process by a matrix-exponential distribution, requiring only that the inter-arrival distribution has a rational Laplace transform. Several distributions are considered as the non-Poissonian traffic. The resulting model uses matrix algebraic techniques only, thus not requiring any complex and/or tedious transform techniques. We also incorporate various control policies in our modeling framework using acceptance functions. Through our computational studies, we conclude that the second and the third moments of the non-Poissonian traffic have significant impact on various performance measures.
The First IEEE Gigabit Networking (GBN) Workshop defined a set of characteristics of ''interesting'' high-speed applications. The GBN criteria ensure that the application addresses a significant proble...
详细信息
The First IEEE Gigabit Networking (GBN) Workshop defined a set of characteristics of ''interesting'' high-speed applications. The GBN criteria ensure that the application addresses a significant problem, and that it actually requires a gigabit network. This paper presents five challenges that augment the GBN criteria. These challenges ask whether gigabit applications require new research into different protocols, or can be supported by existing protocols that merely run faster.
Combinatorial branch and bound searches are a common technique for solving global optimisation and decision problems. Their performance often depends on good search order heuristics, refined over decades of algorithms...
详细信息
Combinatorial branch and bound searches are a common technique for solving global optimisation and decision problems. Their performance often depends on good search order heuristics, refined over decades of algorithms research. Parallel search necessarily deviates from the sequential search order, sometimes dramatically and unpredictably, e.g. by distributing work at random. This can disrupt effective search order heuristics and lead to unexpected and highly variable parallel performance. The variability makes it hard to reason about the parallel performance of combinatorial searches. This paper presents a generic parallel branch and bound skeleton, implemented in Haskell, with replicable parallel performance. The skeleton aims to preserve the search order heuristic by distributing work in an ordered fashion, closely following the sequential search order. We demonstrate the generality of the approach by applying the skeleton to 40 instances of three combinatorial problems: Maximum Clique, 0/1 Knapsack and Travelling Salesperson. The overheads of our Haskell skeleton are reasonable: giving slowdown factors of between 1.9 and 6.2 compared with a class-leading, dedicated, and highly optimised C++ Maximum Clique solver. We demonstrate scaling up to 200 cores of a Beowulf cluster, achieving speedups of 100x for several Maximum Clique instances. We demonstrate low variance of parallel performance across all instances of the three combinatorial problems and at all scales up to 200 cores, with median Relative Standard Deviation (RSD) below 2%. Parallel solvers that do not follow the sequential search order exhibit far higher variance, with median RSD exceeding 85% for Knapsack. (C) 2017 The Author(s). Published by Elsevier Inc.
The first-order effects of interchannel noise correlation on the fasle alarm and incorrect dismissal probabilities are computed for a bank of parallel RLC filters by expanding the envelope distribution of the n filter...
详细信息
The first-order effects of interchannel noise correlation on the fasle alarm and incorrect dismissal probabilities are computed for a bank of parallel RLC filters by expanding the envelope distribution of the n filter outputs in a power series. The correction to the false alarm probability due to noise correlation is found to decrease with increasing threshold-to-rms-noise ratios. If the filter-separation-to-filter-bandwidth ratios are larger than 0.2, it is less than 15 and 0.2 per cent for threshold-to-rms-noise ratios exceeding 12 and 14 db respectively. The correction to the incorrect dismissal probability, which is computed by considering the signal output of three contiguous filters, increases with increasing threshold-to-rms-noise and signal-to-threshold ratios. Even for filter separations larger than the filter bandwidth, it may be in excess of 100 per cent if the threshold-to-rms-noise ratio exceeds 12 db and the signal-to-threshold ratio is larger than 1.2.
This paper investigates the problem of specifying and implementing physical boundary conditions for the Monte Carlo (MC) simulation of electron dynamics in semiconductor devices. The goal of this work is to establish ...
详细信息
This paper investigates the problem of specifying and implementing physical boundary conditions for the Monte Carlo (MC) simulation of electron dynamics in semiconductor devices. The goal of this work is to establish an accurate and efficient ohmic boundary condition scheme for use in characterizing realistic device structures. In this work, three distinct physical models for specifying the boundary electrons at the ideal ohmic contacts of an N+ - N - N+ GaAs Ballistic diode structure are investigated. This study demonstrates that a displaced Maxwellian scheme, which allows for an electron ensemble with momentum space displacement and random spread, presents definite computational advantages when one is interested in resolving asymmetries in the electron distribution function throughout the semiconductor device structure.
暂无评论