Browsing by Subject "Fault tolerance"
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Item Open Access An adaptive, energy-aware and distributed fault-tolerant topology-control algorithm for heterogeneous wireless sensor networks(Elsevier BV, 2016) Deniz, F.; Bagci, H.; Korpeoglu, I.; Yazıcı A.This paper introduces an adaptive, energy-aware and distributed fault-tolerant topology-control algorithm, namely the Adaptive Disjoint Path Vector (ADPV) algorithm, for heterogeneous wireless sensor networks. In this heterogeneous model, we have resource-rich supernodes as well as ordinary sensor nodes that are supposed to be connected to the supernodes. Unlike the static alternative Disjoint Path Vector (DPV) algorithm, the focus of ADPV is to secure supernode connectivity in the presence of node failures, and ADPV achieves this goal by dynamically adjusting the sensor nodes' transmission powers. The ADPV algorithm involves two phases: a single initialization phase, which occurs at the beginning, and restoration phases, which are invoked each time the network's supernode connectivity is broken. Restoration phases utilize alternative routes that are computed at the initialization phase by the help of a novel optimization based on the well-known set-packing problem. Through extensive simulations, we demonstrate that ADPV is superior in preserving supernode connectivity. In particular, ADPV achieves this goal up to a failure of 95% of the sensor nodes; while the performance of DPV is limited to 5%. In turn, by our adaptive algorithm, we obtain a two-fold increase in supernode-connected lifetimes compared to DPV algorithm.Item Open Access CAPSULE: Language and system support for efficient state sharing in distributed stream processing systems(ACM, 2012) Losa, G.; Kumar, V.; Andrade, H.; Gedik, Buğra; Hirzel, M.; Soulé, R.; Wu, K. -L.Data stream processing applications are often expressed as data flow graphs, composed of operators connected via streams. This structured representation provides a simple yet powerful paradigm for building large-scale, distributed, high-performance applications. However, there are many tasks that require sharing data across operators, and across operators and the runtime using a less structured mechanism than point-to-point data flows. Examples include updating control variables, sending notifications, collecting metrics, building collective models, etc. In this paper we describe CAPSULE, which fills this gap. CAPSULE is a code generation and runtime framework that offers an easy to use and highly flexible framework for developers to realize shared variables (CAPSULE term for shared state) by specifying a data structure (at the programming-language level), and a few associated configuration parameters that qualify the expected usage scenario. Besides the easy of use and flexibility, CAPSULE offers the following important benefits: (1) Custom Code Generation - CAPSULE makes use of user-specified configuration parameters and information from the runtime to generate shared variable servers that are tailored for the specific usage scenario, (2) Composability - CAPSULE supports deployment time composition of the shared variable servers to achieve desired levels of scalability, performance and fault-tolerance, and (3) Extensibility - CAPSULE provides simple interfaces for extending the CAPSULE framework with more protocols, transports, caching mechanisms, etc. We describe the motivation for CAPSULE and its design, report on its implementation status, and then present experimental results. Copyright © 2012 ACM.Item Open Access A distributed tault-tolerant topology control algorithm for heterogeneous wireless sensor networks(Institute of Electrical and Electronics Engineers, 2015-04) Bagci, H.; Korpeoglu, I.; Yazıcı, A.This paper introduces a distributed fault-tolerant topology control algorithm, called the Disjoint Path Vector (DPV), for heterogeneous wireless sensor networks composed of a large number of sensor nodes with limited energy and computing capability and several supernodes with unlimited energy resources. The DPV algorithm addresses the k-degree Anycast Topology Control problem where the main objective is to assign each sensor's transmission range such that each has at least k-vertex-disjoint paths to supernodes and the total power consumption is minimum. The resulting topologies are tolerant to k - 1 node failures in the worst case. We prove the correctness of our approach by showing that topologies generated by DPV are guaranteed to satisfy k-vertex supernode connectivity. Our simulations show that the DPV algorithm achieves up to 4-fold reduction in total transmission power required in the network and 2-fold reduction in maximum transmission power required in a node compared to existing solutions.Item Open Access Energy cost model for frequent item set discovery in unstructured P2P networks(Springer, London, 2012) Cem, E.; Demirkaya, Ender; Esiner, E.; Ozaydin, B.; Ozkasap O.For large scale distributed systems, designing energy efficient protocols and services has become as significant as considering conventional performance criteria like scalability, reliability, fault-tolerance and security. We consider frequent item set discovery problem in this context. Although it has attracted attention due to its extensive applicability in diverse areas, there is no prior work on energy cost model for such distributed protocols. In this paper, we develop an energy cost model for frequent item set discovery in unstructured P2P networks. To the best of our knowledge, this is the first study that proposes an energy cost model for a generic peer using gossip-based communication. As a case study protocol, we use our gossip-based approach ProFID for frequent item set discovery. After developing the energy cost model, we examine the effect of protocol parameters on energy consumption using our simulation model on PeerSim and compare push-pull method of ProFID with the well-known push-based gossiping approach. Based on the analysis results, we reformulate the upper bound for the peer's energy cost. © 2012 Springer-Verlag London Limited.Item Open Access Fault tolerant control for over-actuated systems: an adaptive correction approach(IEEE, 2016) Tohidi, Seyed Shahabaldin; Yıldız, Yıldıray; Kolmanovsky, İ.This paper proposes an adaptive fault tolerant control allocation approach for over-actuated systems. The methodology does not utilize the control input matrix estimation to tolerate actuator faults and, therefore, the proposed control allocation method does not require persistence of excitation. Adaptive control approach with a closed loop reference model is used for identifying control allocation parameters, which provides improved performance without introducing undesired oscillations. Furthermore, a sliding mode controller is used to guarantee the outer loop asymptotic stability. Simulation results are provided, where the ADMIRE model is used as an over-actuated system, to demonstrate the effectiveness of the proposed method.Item Open Access A fault-tolerant hexagonal systolic array(Elsevier, 1992) Aykanat, Cevdet; Özgüner, F.Item Open Access Fault-tolerant irregular topology design method for network-on-chips(IEEE, 2014) Tosun, S.; Ajabshir V.B.; Mercanoglu O.; Öztürk, ÖzcanAs the technology sizes of integrated circuits (ICs) scale down rapidly, current transistor densities on chips dramatically increase. While nanometer feature sizes allow denser chip designs in each technology generation, fabricated ICs become more susceptible to wear-outs, causing operation failure. Even a single link failure within an on-chip fabric can halt communication between application blocks, which makes the entire chip useless. In this study, we aim to make faulty chips designed with Network-on-Chip (NoC) communication usable. Specifically, we present a fault-tolerant irregular topology generation method for application specific NoC designs. Designed NoC topology allows a different routing path if there is a link failure on the default routing. We compare fault-tolerant topologies with regular fault-tolerant ring topologies, and non-fault-tolerant application specific irregular topologies on energy consumption, performance, and area using multimedia benchmarks and custom-generated graphs. © 2014 IEEE.Item Open Access Fault-tolerant topology generation method for application-specific network-on-chips(Institute of Electrical and Electronics Engineers, 2015) Tosun, S.; Ajabshir, V. B.; Mercanoglu, O.; Ozturk, O.As the technology sizes of integrated circuits (ICs) scale down rapidly, current transistor densities on chips dramatically increase. While nanometer feature sizes allow denser chip designs in each technology generation, fabricated ICs become more susceptible to wear-outs, causing operation failure. Even a single link failure within an on-chip fabric can halt communication between application blocks, which makes the entire chip useless. In this paper, we aim to make faulty chips designed with network-on-chip (NoC) communication usable. Specifically, we present fault-tolerant irregular topology-generation method for application-specific NoC designs. Designed NoC topology allows different routing path if there is a link failure on the default routing path. Additionally, we present a simulated annealing-based application mapping algorithm aiming to minimize total energy consumption of the NoC design. We compare fault-tolerant topologies with nonfault-tolerant application-specific irregular topologies on energy consumption, performance, and area using multimedia benchmarks and custom-generated graphs. Our results demonstrate that our method is able to determine fault-tolerant topologies with negligible area increase and better energy values.Item Open Access Feature-based rationale management system for supporting software architecture adaptation(World Scientific Publishing Co. Pte. Ltd., 2012) Tekinerdogan, B.; Sozer, H.; Aksit, M.Each software architecture design is the result of a broad set of design decisions and their justifications, that is, the design rationale. Capturing the design rationale is important for a variety of reasons such as enhancing communication, reuse and maintenance. Unfortunately, it appears that there is still a lack of appropriate methods and tools for effectively capturing and managing the architecture design rationale. In this paper we present a feature-based rationale management approach and the corresponding tool environment ArchiRationale for supporting software architecture adaptation. The approach takes as input an existing architecture and captures the design rationale for adapting the architecture for a given quality concern. For this we define a feature model that includes the possible set of architectural tactics to realize the quality concern. The presented approach captures the rationale for deciding on feature selections and for selecting the corresponding architecture design alternatives. ArchiRationale customizes and integrates the Eclipse plugin tools XFeature, ArchStudio and XQuery to provide tool support for capturing, storing and accessing the design rationale. We illustrate the approach for adapting a software architecture for fault tolerance. © 2012 World Scientific Publishing Company.Item Open Access Flora: a framework for decomposing software architecture to introduce local recovery(John Wiley & Sons Ltd., 2009-07) Sözer, H.; Tekinerdoǧan, B.; Akşit, M.The decomposition of software architecture into modular units is usually driven by the required quality concerns. In this paper we focus on the impact of local recovery concern on the decomposition of the software system. For achieving local recovery, the system needs to be decomposed into separate units that can be recovered in isolation. However, it appears that this required decomposition for recovery is usually not aligned with the decomposition based on functional concerns. Moreover, introducing local recovery to a software system, while preserving the existing decomposition, is not trivial and requires substantial development and maintenance effort. To reduce this effort we propose a framework that supports the decomposition and implementation of software architecture for local recovery. The framework provides reusable abstractions for defining recoverable units and the necessary coordination and communication protocols for recovery. We discuss our experiences in the application and evaluation of the framework for introducing local recovery to the open-source media player called MPlayer. Copyright 2009 John Wiley & Sons, Ltd.Item Open Access FPGA implementation of a fault-tolerant application-specific NoC design(IEEE, 2016-04) Yeşil, Şerif; Tosun, S.; Öztürk, ÖzcanToday's integrated circuits are more susceptible to permanent link failures than before as a result of diminishing technology sizes. Even a single link failure can make an entire chip useless. Single link failure problem is fatal to application-specific Network-on-Chip (NoC) designs as well if they cannot tolerate such failures. One solution to this problem can be having alternative routing options on the network for each communicating pair. In this study, we present an FPGA implementation of such a method for application-specific NoCs. This method adds additional network resources to the non-fault-tolerant design in an attempt to make it fault-tolerant. We show the effects of the presented fault-tolerant method on an FPGA implementation of Mp3 encoder based on energy consumption and area increase against non-fault-tolerant case. © 2016 IEEE.Item Open Access Instruction-level reliability improvement for embedded systems(IEEE, 2020-09) Tekgül, Hakan; Öztürk, ÖzcanWith the increasing number of applications in embedded computing systems, it became indispensable for the system designers to consider multiple objectives including power, performance, and reliability. Among these, reliability is a bigger constraint for safety critical applications. For example, fault tolerance of transportation systems has become very critical with the use of many embedded on-board devices. There are many techniques proposed in the past decade to increase the fault tolerance of such systems. However, many of these techniques come with a significant overhead, which make them infeasible in most of the embedded execution scenarios. Motivated by this observation, our main contribution in this paper is to propose and evaluate an instruction criticality based reliable source code generation algorithm. Specifically, we propose an instruction ranking formula based on our detailed fault injection experiments. We use instruction rankings along with the overhead tolerance limits and generate a source code with increased fault tolerance. The primary goal behind this work is to improve reliability of an application while keeping the performance effects minimal. We apply state-of-the-art reliability techniques to evaluate our approach on a set of benchmarks. Our experimental results show that, the proposed approach achieves up to 8% decrease in error rates with only 10% performance overhead. The error rates further decrease with higher overhead tolerances.Item Open Access Optimizing decomposition of software architecture for local recovery(Springer New York LLC, 2013) Sözer, H.; Tekinerdoǧan, B.; Akşit, M.The increasing size and complexity of software systems has led to an amplified number of potential failures and as such makes it harder to ensure software reliability. Since it is usually hard to prevent all the failures, fault tolerance techniques have become more important. An essential element of fault tolerance is the recovery from failures. Local recovery is an effective approach whereby only the erroneous parts of the system are recovered while the other parts remain available. For achieving local recovery, the architecture needs to be decomposed into separate units that can be recovered in isolation. Usually, there are many different alternative ways to decompose the system into recoverable units. It appears that each of these decomposition alternatives performs differently with respect to availability and performance metrics. We propose a systematic approach dedicated to optimizing the decomposition of software architecture for local recovery. The approach provides systematic guidelines to depict the design space of the possible decomposition alternatives, to reduce the design space with respect to domain and stakeholder constraints and to balance the feasible alternatives with respect to availability and performance. The approach is supported by an integrated set of tools and illustrated for the open-source MPlayer software. © 2011 Springer Science+Business Media, LLC.