Hierarchical Partitioning Techniques for Structured Adaptive Mesh Refinement Applications

This paper presents the design and preliminary evaluation of hierarchical partitioning and load-balancing techniques for distributed structured adaptive mesh refinement (SAMR) applications. The overall goal of these techniques is to enable the load distribution to reflect the state of the adaptive grid hierarchy and exploit it to reduce synchronization requirements, improve load-balance, and enable concurrent communications and incremental redistribution. The hierarchical partitioning algorithm (HPA) partitions the computational domain into subdomains and assigns them to hierarchical processor groups. Two variants of HPA are presented in this paper. The static hierarchical partitioning algorithm (SHPA) assigns portions of overall load to processor groups. In SHPA, the group size and the number of processors in each group is setup during initialization and remains unchanged during application execution. It is experimentally shown that SHPA reduces communication costs as compared to the Non-HPA scheme, and reduces overall application execution time by up to 59%. The adaptive hierarchical partitioning algorithm (AHPA) dynamically partitions the processor pool into hierarchical groups that match the structure of the adaptive grid hierarchy. Initial evaluations of AHPA show that it can reduce communication costs by up to 70%.     

An orthogonal genetic algorithm for multimedia multicast routing

Many multimedia communication applications require a source to send multimedia information to multiple destinations through a communication network. To support these applications, it is necessary to determine a multicast tree of minimal cost to connect the source node to the destination nodes subject to delay constraints on multimedia communication. This problem is known as multimedia multicast routing and has been proved to be NP-complete. The paper proposes an orthogonal genetic algorithm for multimedia multicast routing. Its salient feature is to incorporate an experimental design method called orthogonal design into the crossover operation. As a result, it can search the solution space in a statistically sound manner and it is well suited for parallel implementation and execution. We execute the orthogonal genetic algorithm to solve two sets of benchmark test problems. The results indicate that for practical problem sizes, the orthogonal genetic algorithm can find near optimal solutions within moderate numbers of generations     

基于节点集计算能力差异的Hadoop自适应任务调度算法

针对异构集群任务推测式执行算法存在的任务进度比例固定、落后任务被动选取等问题,提出基于快慢节点集计算能力差异的自适应任务调度算法。该算法量化节点集计算能力差异实现分集调度,并通过节点与任务速率的动态反馈及时更新快慢节点集,提高节点集资源利用率与任务并行度。在两节点集中,利用动态调整任务进度比例判别落后任务,主动选择采用替代执行方式为落后任务执行备份任务的快节点,从而提升任务执行效率。与最长近似结束时间(LATE)算法的实验对比结果表明,该算法在短作业集、混合型作业集、出现节点性能下降的混合型作业集执行时间上比LATE算法分别缩短了5.21%、20.51%、23.86%,启用的备份任务数比LATE算法明显减少。所提算法可使任务主动适应节点差异,在减少备份任务的同时有效提高作业整体执行效率。     

一种主动网络通信平台的设计与开发

当具有可编程特点的主动网络技术应用到网络管理系统中时,网管终端与主动节点之间以及主动节点与主动节点之间的交互,主动代码的加载等需要得到基础通信服务的支撑.本文主要针对我们提出的基于主动网络的面向业务的网管系统的具体通信需要,分析了应该具备的通信功能,设计了执行环境和主动信包封装格式,基于分布式的主动代码存储机制实现了主动代码的动态加载,从而设计和并发了一种主动网络通信平台.该平台在网管原型系统得到了运用,从运用结果看它能够较好的进行主动代码的动态加载,能够提供基础的通信服务.     

K6 — a protected mode kernel for the iAPX286

This paper presents the design of an operating system kernel offering protection, and using the object model as the design methodology. Rich communication facilities are provided between domains of protection allowing stimuli, data and objects to be passed. All object types, including protection domains, may be created and deleted dynamically, and some may be ‘sealed’ and employed as user-defined objects by a type manager which alone can penetrate them.     

Achieving Robustness and Minimizing Overhead in Parallel Algorithms Through Overlapped Communication/Computation

One of the major goals in the design of parallel processing machines and algorithms is to achieve robustness and reduce the effects of the overhead introduced when a given problem is parallelized or a fault occurs. A key contributor to overhead is communication time, in particular when a node is faulty and another node is substuiting for its operation. Many architectures try to reduce this overhead by minimizing the actual time for a communication to occur, including latency and bandwidth figures. Another approach is to hide communication by overlapping it with computation assuming that the computation is the most prominent factor. This paper presents the mechanisms provided in the Proteus parallel computer and its effective use of communication hiding through overlapping communication/computation techniques with and without the presence of a fault. These techniques are easily extended for use in compiler support of parallel programming. We also address the complexity (or rather simplicity) in achieving complete exchange on the Proteus Machine.     

Mobile Agent的远程代码动态装配研究

针对Mobile Agent整体迁移时的缺点，文中提出了Mobile Agent的远程代码动态装配思想，即把部分执行代码存放在迁移节点，Agent在此节点运行时进行动态组装，运行完毕后动态拆卸。探讨了在此思想下Agent实体以及Agent Server的结构，分析了Agent的执行流程和执行效率。     

Modelling real-time applications based on resource reservations

This paper presents a strategy for the design of real-time applications relying on the resource-reservation paradigm, based on a new modelling element that describes the schedulable entities of the applications during the whole design cycle. A virtual view of this element is used first for evaluating a set of constraints that guarantee the application schedulability independently of the execution platform. Then, the element is viewed as a thread that receives the particular scheduling parameters required for a schedulable execution of the application in a specific platform. The purpose of the design process is to make both views compatible.     

A framework for mapping periodic real-time applications onmulticomputers

This short paper presents a framework for periodic execution of task-flow graphs that enables schedulability analysis of the communication requirements. The analysis performs the steps of segmenting messages, assigning the segments to specific links and time intervals, and ordering them within the intervals to generate node switching schedules that provide contention-free message routing at run-time. The analysis is also used to integrate task allocation with message routing using a contention-based objective function. Usefulness of the proposed scheme in ensuring guaranteed communication performance is demonstrated by an appropriate example     

边缘计算中协作计算卸载与动态任务调度

在边缘计算场景中,通过将部分待执行任务卸载到边缘服务器执行能够达到降低移动设备的负载、提升移动应用性能和减少设备开销的目的.对于时延敏感任务,只有在截止期限内完成才具有实际意义.但是边缘服务器的资源往往有限,当同时接收来自多个设备的数据传输及处理任务时,可能造成任务长时间的排队等待,导致部分任务因超时而执行失败,因此无法兼顾多个设备的性能目标.鉴于此,在计算卸载的基础上优化边缘服务器端的任务调度顺序.一方面,将时延感知的任务调度建模为一个长期优化问题,并使用基于组合多臂赌博机的在线学习方法动态调整服务器的调度顺序.另一方面,由于不同的任务执行顺序会改变任务卸载性能提升程度,因而影响任务卸载决策的有效性.为了增加卸载策略的鲁棒性,采用了带有扰动回报的深度Q学习方法决定任务执行位置.仿真算例证明了该策略可在平衡多个用户目标的同时减少系统的整体开销.     

A location model for smart environments

This paper presents a location model for location-aware and user-aware services in smart environments. It can be dynamically organized like a tree based on geographical containment, such as that in a user–room–floor–building hierarchy and each node in the tree can be constructed as an executable software component. The model is unique in existing approaches because it enables location-aware services to be managed without any database servers, it can be managed by multiple computers, and it can provide a unified view of the locations of not only physical entities and spaces, including users and objects, but also computing devices and services. A prototype implementation of this approach was constructed on a Java-based mobile agent system. This paper presents the rationale, design, implementation, and applications of the prototype system.     

A survey on software checkpointing and mobility techniques in distributed systems

This paper has two purposes. First, it shows that existing solutions employing checkpointing and mobility in distributed applications, fix, at design time, the types and the techniques of checkpointing and mobility to be employed at runtime. Second, it provides policies allowing the dynamic selection of checkpointing and mobility techniques according to the execution environment. For that, this paper presents checkpointing and mobility techniques to evaluate them in order to identify their advantages and their shortcomings, and then determine the appropriate execution conditions in which a specific mobility technique becomes beneficial. This investigation will allow in assisting adaptation plans' generation and promoting future research in the area of self‐adaptivity of distributed applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Communication‐aware thread mapping using the translation lookaside buffer

Threads of parallel applications need to communicate in order to fulfill their tasks. The communication performance between the cores in modern multi‐core architectures differs because of the memory and interconnection hierarchies. In these architectures, it is important to map the threads of parallel applications by taking into account the communication between them, to improve their performance and energy consumption. In parallel applications based on shared memory, communication is implicit, which makes it difficult to detect the communication pattern between the threads. In this paper, we introduce a new lightweight mechanism to detect the communication pattern between threads of shared memory applications using the translation lookaside buffer. Our mechanism relies on hardware features, which make it transparent to the programmer and allow the detection to be performed by the operating system during the execution of the application. We also developed a heuristic mapping algorithm that uses the detected pattern to dynamically map the threads to cores. Experiments were performed with applications from the NAS‐OMP and PARSEC parallel benchmark suites in a simulated machine as well as a real machine. Results show that our mechanism can substantially improve parallel application performance, as well as processor and DRAM energy consumption. Copyright © 2015 John Wiley & Sons, Ltd.     

Autonomous and adaptive resource allocation among multiple nodes and multiple applications in heterogeneous wireless networks

In the forthcoming future, various means of wireless communication, such as cellular, Wi-Fi, WiMAX, and DSRC, will be available to mobile users and applications. With the development of wireless communication and mobile devices, more and more users and applications will be accommodated in mobile environment. Since mobile users and applications compete for the limited wireless resources whose communication quality dynamically change, we need an adaptive mechanism for mobile users and applications to share the available network resources while satisfying each application?s QoS requirements. In this paper, we propose an adaptive resource allocation mechanism where each node autonomously determines wireless network resources to assign to each of networked applications running on it. For this purpose, we adopt an attractor composition model, which is based on an autonomous and adaptive behavior of biological systems. Through numerical analysis, we confirmed that our mechanism could adaptively and stably allocate wireless network resources to applications, while considering their QoS requirements and fairly sharing network resources with other nodes. It also is shown that our mechanism superiors to a mechanism where a node determines resource allocation by solving an optimization problem.     

An Optimization-Based Approach for Design Project Scheduling

Concurrent engineering has been widely used in managing design projects to speed up the design process by concurrently performing multiple tasks. Since the progress of a design task often depends on the knowledge about other tasks and requires effective communication, tasks and communication activities need to be properly coordinated to avoid delays caused by waiting for information or the need for rework. This paper presents a novel formulation for design project scheduling with explicit modeling of task dependencies and the associated communication activities. General dependencies are modeled as combinations of three basic types representing sequential, concurrent, and independent processes. Communication activities are also modeled as tasks, and their interactions with design tasks are described by sets of intertask constraints. The objective is to achieve timely project completion with limited resources. To improve algorithm convergence and schedule quality, penalties on the violation of constraints coupling design tasks are added to the objective function. A solution methodology that combines Lagrangian relaxation, dynamic programming, and heuristic is developed to schedule design and communication tasks, and a surrogate optimization framework is used to overcome the “inseperability” caused by nonadditive penalties. A heuristic procedure is then developed to obtain scheduling policies from optimization results and to dynamically construct schedules. Numerical results show that the approach is effective to handle various task dependencies and the associated communication activities to provide high-quality schedules.      

Providing multiple hard latency and throughput guarantees for packet switching networks on chip

In many-core architectures different distributed applications are executed in parallel. The applications may need hard guarantees for communication with respect to latency and throughput to cope with their constraints. Networks on Chip (NoC) are the most promising approach to handle these requirements in architectures with a large number of cores. Dynamic reservation of communication resources in virtual channel NoCs is used to enable quality of service for concurrent communication. This paper presents a router design supporting best effort and connection-oriented guaranteed service communication. The communication resources are shared dynamically between the two communication schemes. The key contribution is a concept for virtual channel reservation supporting different bandwidth and latency guarantees for simultaneous guaranteed service communication flows. Different to state-of-the-art, the used scheduling approach allows to give hard guarantees regarding throughput and latency. The concept enables to adjust the bandwidth and latency requirements of connections at run-time to cope with dynamically changing application requirements. Due to its distributed reservation process and resource allocation it offers good scalability for many-core architectures. The implementation of a router and the required extension of a network interface to support the proposed concept are presented. The software perspective is discussed. An algorithm is presented that is used to establish guaranteed service connections according to the applications bandwidth requirements. Simulation results are compared to state-of-the-art arbitration schemes and show significant improvements of latency and throughput, e.g. for an MPEG4 application. Synthesis results expose the low area overhead and impact on energy consumption which makes the concepts highly attractive for QoS-constraint many-core architectures.     

Dynamically negotiated resource management for data intensiveapplication suites

In contemporary computers and networks of computers, various application domains are making increasing demands on the system to move data from one place to another, particularly under some form of soft real-time constraint. A brute force technique for implementing applications in this type of domain demands excessive system resources, even though the actual requirements by different parts of the application vary according to the way it is being used at the moment. A more sophisticated approach is to provide applications with the ability to dynamically adjust resource requirements according to their precise needs, as well as the availability of system resources. This paper describes a set of principles for designing systems to provide support for soft real-time applications using dynamic negotiation. Next, the execution level abstraction is introduced as a specific mechanism for implementing the principles. The utility of the principles and the execution level abstraction is then shown in the design of three resource managers that facilitate dynamic application adaptation: Gryphon, EPA/RT-PCIP, and the DQM architectures     

一种面向普适计算的适应性软件体系结构风格

普适计算软件需要适应用户需求和运行环境的动态变化.这一特点使得软件复杂度空前增加,迫切需要以软件体系结构为代表的架构/设计层面重用手段来支持其高效开发.在以适应性为中心的普适计算空间抽象模型基础上,提出了一种面向普适计算的软件体系结构风格UbiArch,并从概念视图、运行视图和开发视图这3个维度对该软件体系结构风格进行了阐述.UbiArch支持软件实体按需加入应用、主动适应环境的行为模式,实现了软件适应能力的高层次重用,同时与构件等成熟软件技术的紧密结合也保证了其可实践性.支撑该体系结构风格的软件平台原型系统及其上的应用验证了UbiArch的有效性和通用性.     

P2P-MPI: A Peer-to-Peer Framework for Robust Execution of Message Passing Parallel Programs on Grids

This paper presents P2P-MPI, a middleware aimed at computational Grids. From the programmer point of view, P2P-MPI provides a message-passing programming model which enables the development of MPI applications for Grids. Its originality lies in its adaptation to unstable environments. First, the peer-to-peer design of P2P-MPI allows for a dynamic discovery of collaborating resources. Second, it gives the user the possibility to adjust the robustness of an execution thanks to an internal process replication mechanism. Finally, we measure the performance of the integrated message passing library on several benchmarks and on different hardware platforms.     

基于哈希链与同步性机制的Modbus/TCP安全认证协议

针对Modbus/TCP协议的安全缺陷,基于密码学技术提出一种安全的Modbus协议（Sec_Modbus协议）：采用对称加密和数字签名技术实现保密性要求及认证,利用同步性原理和哈希函数的单向性设计基于哈希链的防重放方法,通过随机函数产生索引号动态指定通信密钥,最终在不增加通信过程的情况下实现安全通信。实验结果表明：Sec_Modbus协议能够防止攻击者针对指令的认证类攻击、中间人攻击及重放攻击,与已有方法相比,该方法不仅安全性更高,且具有更好的时间性能,能更好地满足工业控制系统对安全性及实时性的要求。