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    Task migration in three-dimensional meshes

    , Article Journal of Supercomputing ; 2010 , Pages 1-25 ; 09208542 (ISSN) Bargi, A ; Sarbazi Azad, H ; Sharif University of Technology
    Abstract
    As a result of the emerging use of mesh-based multicomputers (and recently mesh-based multiprocessor systems-on-chip), issues related to processor management have attracted much attention. In a mesh-based multiprocessor, after repeated submesh allocations and de-allocations, the system network may be fragmented, i.e. there might be unallocated nodes in the network. As a result, in a system with contiguous processor allocation, no new tasks can start running due to the lack of enough free adjacent processors to form a suitable submesh. Although there might be enough free processors available, they remain idle until the allocator can find a set of adjacent free nodes forming a submesh to be... 

    Intruder capturing in mesh and torus networks

    , Article International Journal of Foundations of Computer Science ; Volume 19, Issue 4 , 2008 , Pages 1049-1071 ; 01290541 (ISSN) Imani, N ; Sarbazi Azad, H ; Zomaya, A ; Sharif University of Technology
    2008
    Abstract
    In this paper, we propose a solution for the problem of capturing an intruder in two popular interconnection topologies namely, the mesh and the torus. A set of agents collaborate to capture a hostile intruder in the network. While the agents can move in the network one hop at a time, the intruder is assumed to be arbitrarily fast i.e. it can traverse any number of nodes contiguously as far as there are no agents in those nodes. Here we consider a new version of the problem where each agent can replicate new agents when needed, i.e. the algorithm starts with a single agent and new agents are created on demand. We define a new class of algorithms for capturing an intruder. In particular, we... 

    A mathematical model of deterministic wormhole routing in hypercube multicomputers using virtual channels

    , Article Applied Mathematical Modelling ; Volume 27, Issue 12 , 2003 , Pages 943-953 ; 0307904X (ISSN) Sarbazi Azad, H ; Sharif University of Technology
    Elsevier Inc  2003
    Abstract
    Although several analytical models have been proposed in the literature for binary n-cubes with deterministic routing, most of them have not included the effects of virtual channel multiplexing on network performance. The only mathematical model for deterministic wormhole routing in hypercubes with virtual channels was proposed in [Y. Boura, Design and Analysis of Routing Schemes and Routers for Wormhole-routed Mesh Architectures, Ph.D. Thesis, Department of Computer Science and Engineering, Pennsylvania State University, 1995] which uses complex combinatorial analysis with a computation time of O(N = 2n) for an n-dimensional hypercube. This paper proposes a new and simple analytical model... 

    A parallel algorithm for Lagrange interpolation on the cube-connected cycles

    , Article Microprocessors and Microsystems ; Volume 24, Issue 3 , 2000 , Pages 135-140 ; 01419331 (ISSN) Sarbazi Azad, H ; Ould-Khaoua, M ; Mackenzie, L. M ; Sharif University of Technology
    Elsevier  2000
    Abstract
    This paper introduces a parallel algorithm for computing an N = n2n point Lagrange interpolation on an n-dimensional cube-connected cycles (CCCn). The algorithm consists of three phases: initialisation, main and final. While there is no computation in the initialisation phase, the main phase is composed of n2n-1 steps, each consisting of four multiplications, four subtractions and one communication operation, and an additional step including one division and one multiplication. The final phase is carried out in two sub-phases. There are [n/2] steps in the first sub-phase, each including two additions and one communication, followed by the second sub-phase which comprises n steps each... 

    Analytical performance modelling of adaptive wormhole routing in the star interconnection network

    , Article 20th IEEE International Parallel and Distributed Processing Symposium, IPDPS 2006, 25 April 2006 through 29 April 2006 ; Volume 2006 , 2006 ; 1424400546 (ISBN); 9781424400546 (ISBN) Kiasari, A. E ; Sarbazi Azad, H ; Ould Khaoua, M ; Sharif University of Technology
    IEEE Computer Society  2006
    Abstract
    The star graph was introduced as an attractive alternative to the well-known hypercube and its properties have been well studied in the past. Most of these studies have focused on topological properties and algorithmic aspects of this network. Although several analytical models have been proposed in the literature for different interconnection networks, none of them have dealt with star graphs. This paper proposes the first analytical model to predict message latency in wormhole-switched star interconnection networks with fully adaptive routing. The analysis focuses on a fully adaptive routing algorithm which has shown to be the most effective for star graphs. The results obtained from... 

    On the topological properties of grid-based interconnection networks: Surface area and volume of radial spheres

    , Article Computer Journal ; Vol. 54, issue. 5 , 2011 , p. 726-737 ; ISSN: 00104620 Sarbazi-Azad, H ; Khonsari, A ; Ould-Khaoua, M ; Sharif University of Technology
    Abstract
    Grid-based networks (or grids for short), such as meshes and tori, have been the underlying topology for many multicomputers, and have been extensively studied in the past as a graph topology. In this paper, we investigate some topological properties of grids without boundary wrap-around (meshes) and with boundary wrap-around (tori). In particular, we study the problem of finding the number of nodes located at/within a given distance from a given node (surface area/volume) in the network and derive some expressions for computing such a number. Furthermore, we provide similar expressions that improve on previous results already reported in the literature for some special cases of grids,... 

    An empirical performance analysis of minimal and non-minimal routing in cube-based OTIS multicomputers

    , Article Journal of High Speed Networks ; Volume 16, Issue 2 , 2007 , Pages 133-155 ; 09266801 (ISSN) Hashemi Najaf Abadi, H ; Sarbazi Azad, H ; Sharif University of Technology
    2007
    Abstract
    In this study, the performance of virtual cut-through switching in the cube-based OTIS architecture, an optoelectronic interconnection architecture for multicomputer systems, is empirically analyzed. Deadlock-free deterministic and adaptive minimal path routing algorithms for this architecture are introduced, and the effects of different network and traffic parameters on average message latency are investigated. This analysis presents a relatively more realistic view of the OTIS architecture than that presented in previous work by considering issues related to a lower level of abstraction (the routing and switching of messages). Among other results, the analysis indicates that depending on... 

    Resource placement in networks using chromatic sets of power graphs

    , Article 2nd International Symposium on Computer Science in Russia, CSR 2007, Ekaterinburg, 3 September 2007 through 7 September 2007 ; Volume 4649 LNCS , 2007 , Pages 158-167 ; 03029743 (ISSN); 9783540745099 (ISBN) Imani, N ; Sarbazi Azad, H ; Akl, S.G ; Sharif University of Technology
    Springer Verlag  2007
    Abstract
    In this paper, using the chromatic properties of power graphs we propose a new approach for placing resources in symmetric networks. Our novel placement scheme guarantees a perfect placement when such a solution is feasible in the topology. © Springer-Verlag Berlin Heidelberg 2007  

    Topological properties of stretched graphs

    , Article IEEE International Conference on Computer Systems and Applications, 2006, Sharjah, 8 March 2006 through 8 March 2006 ; Volume 2006 , 2006 , Pages 647-650 ; 1424402123 (ISBN); 9781424402120 (ISBN) Shareghi, P ; Sarbazi Azad, H ; Sharif University of Technology
    IEEE Computer Society  2006
    Abstract
    We study a class of interconnection networks for multiprocessors, called the Stretched-G network, which is based on the base graph G by replacing each edge of the base network with an array of processors. Two interesting features of the proposed topology are its area-efficient VLSI layout and superior scalability over the underlying base network while preserving most of its desirable properties. We conduct a general study on the topological properties of stretched networks. We first obtain their basic topological parameters, after that we present an optimal routing algorithm. We also present a unified approach to obtain the topological properties and the VLSI-layout of an arbitrary stretched... 

    The stretched-hypercube: A VLSI efficient network topology

    , Article 8th International Symposium on Parallel Architectures, Algorithms and Networks, I-SPAN 2005, Las Vegas, NV, 7 December 2005 through 9 December 2005 ; Volume 2005 , 2005 , Pages 462-467 ; 0769525091 (ISBN); 9780769525099 (ISBN) Shareghi, P ; Sarbazi Azad, H ; Sharif University of Technology
    2005
    Abstract
    In this paper, we introduce a new class of interconnection networks for multiprocessor systems which we refer to as Stretched-Hypercubes, or shortly the Stretched-Cube networks. These networks are obtained by replacing an edge of the well-known hypercube network with an array of processors. Two interesting features of the proposed topology are its area-efficient VLSI layout and superior scalability over the traditional hypercube network. Some topological properties of the proposed network are studied. In addition, an area-efficient VLSI layout for the stretched-cube is suggested and some comparisons between the proposed network and previously studied networks such as the star and hypercube... 

    The Recursive Transpose-Connected Cycles (RTCC) interconnection network for multiprocessors

    , Article 20th Annual ACM Symposium on Applied Computing, Santa Fe, NM, 13 March 2005 through 17 March 2005 ; Volume 1 , 2005 , Pages 734-738 Farahabady, M. H ; Sarbazi Azad, H ; Sharif University of Technology
    2005
    Abstract
    In this paper, we propose a new modular topology for interconnection networks, the Recursive Transpose-Connected Cycles (RTCC). The RTCC has a recursive definition quite similar to that of fractal graphs having interesting topological characteristics, making it suitable for utilization as the base topology of large-scale multicomputer interconnection networks. We study important properties of this topology such as diameter, bisection width and issues related to implementation, such as routing algorithms and the average message latency under VLSI layout constraints. In addition, we prove that the RTCC is a Hamiltonian graph, We conclude that, insight of most of the above-mentioned properties,... 

    Constraint-based performance comparison of multi-dimensional interconnection networks with deterministic and adaptive routing strategies

    , Article Computers and Electrical Engineering ; Volume 30, Issue 3 , 2004 , Pages 167-182 ; 00457906 (ISSN) Sarbazi Azad, H ; Sharif University of Technology
    2004
    Abstract
    Several studies have examined the relative performance merits of the torus and hypercube taking into account the channel bandwidth constraints imposed by implementation technology. While the torus has been shown to outperform the hypercube under the constant wiring density constraint, the opposite conclusion has been reached when the constant pin-out constraint is considered. However, all these studies have assumed deterministic routing and have not taken into account the internal hardware cost of routers. This paper re-examines the performance merits of the torus and hypercube using both fully-adaptive and deterministic routing strategies. Moreover, it uses a new cost model which takes into... 

    Towards a more realistic comparative analysis of multicomputer networks

    , Article Concurrency and Computation: Practice and Experience ; Volume 16, Issue 13 , 2004 , Pages 1271-1289 ; 15320626 (ISSN) Sarbazi Azad, H ; Ould Khaoua, M ; Mackenzie, L. M ; Sharif University of Technology
    John Wiley and Sons Ltd  2004
    Abstract
    Several studies have examined the relative performance merits of the torus and hypercube taking into account the channel bandwidth constraints imposed by implementation technology. While the torus has been shown to outperform the hypercube under the constant wiring density constraint, the opposite conclusion has been reached when the constant pin-out constraint is considered. However, these studies have assumed a pure uniform traffic pattern and deterministic routing. The 'uniform traffic' assumption is not always justifiable in practice as there are many real-world parallel applications that exhibit non-uniform traffic patterns, which can create unbalanced traffic such as hotspots in the... 

    Analytical modelling of wormhole-routed k-ary n-cubes in the presence of matrix-transpose traffic

    , Article Journal of Parallel and Distributed Computing ; Volume 63, Issue 4 , 2003 , Pages 396-409 ; 07437315 (ISSN) Sarbazi Azad, H ; Ould-Khaoua, M ; Mackenzie, L. M ; Sharif University of Technology
    Academic Press Inc  2003
    Abstract
    Several analytical models of fully adaptive routing in wormhole-routed k-ary n-cubes under the uniform traffic pattern have recently been proposed in the literature. Although the uniform reference model has been widely used in the past, it is not always true in practice as there are many applications that exhibit non-uniform traffic patterns. There has not been so far any study that describes an analytical model of fully adaptive routing under non-uniform traffic conditions. This paper describes a new analytical model of fully adaptive routing in k-ary n-cubes in the presence of non-uniform traffic generated by matrix-transpose permutations, which is an important communication operation... 

    Design for scalability in enterprise SSDs

    , Article Parallel Architectures and Compilation Techniques - Conference Proceedings, PACT ; 24-27 August , 2014 , p. 417-429 ; ISSN: 1089795X ; ISBN: 9781450328098 Tavakkol, A ; Arjomand, M ; Sarbazi-Azad, H ; Sharif University of Technology
    Abstract
    Solid State Drives (SSDs) have recently emerged as a high speed random access alternative to classical magnetic disks. To date, SSD designs have been largely based on multi-channel bus architecture that confronts serious scalability problems in high-end enterprise SSDs with dozens of flash memory chips and a gigabyte host interface. This forces the community to rapidly change the bus-based inter-flash standards to respond to ever increasing application demands. In this paper, we first give a deep look at how different flash parameters and SSD internal designs affect the actual performance and scalability of the conventional architecture. Our experiments show that SSD performance improvement... 

    A new deterministic fault tolerant wormhole routing strategy for k-ary 2-cubes

    , Article 2010 IEEE International Conference on Computational Intelligence and Computing Research, ICCIC 2010, 28 December 2010 through 29 December 2010 ; 2010 , Pages 14-20 ; 9781424459674 (ISBN) Borhani, A. H ; Movaghar, A ; Cole, R. G ; Sharif University of Technology
    Abstract
    Multicomputers have experienced a rapid development during the last decade. Multicomputers rely on an interconnection network among processors to support the message-passing mechanism. Therefore, the reliability of the interconnection network is very important for the reliability of the whole system. In this paper a new fault-tolerant routing algorithm, which is based on dimension order routing, is proposed for k-ary 2-cubes. Packets are sent to their destination through XY routing algorithm and if this transmission is not possible, YX routing algorithm is applied. The XY routing algorithm nullifies offset in "X" direction before routing in "Y" direction, but the YX routing algorithm first... 

    O-TF and O-FTF, optical fault-tolerant DCNS

    , Article Proceedings - 26th Euromicro International Conference on Parallel, Distributed, and Network-Based Processing, PDP 2018 ; 6 June , 2018 , Pages 639-642 ; 9781538649756 (ISBN) Akbari Rokn Abadi, S ; Koohi, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    Performance of a data center is a function of three features; bandwidth, latency, and reliability. By adopting optical technology in data center network, bandwidth increment, in addition to reduction of transmission latency and power consumption, is achieved. Unfortunately, fault tolerance of the optical networks has raised less attention so far. So in this paper, we propose a fault-tolerant, scalable, and high-performance optical architecture built upon previously proposed O-TF network, with the goal of redundancy optimization and reducing the minimum number of wavelength channels required for non-blocking functionality of the network. Moreover, reducing network diameter, in O-FTF network... 

    Detecting threats in star graphs

    , Article IEEE Transactions on Parallel and Distributed Systems ; Volume 20, Issue 4 , 2009 , Pages 474-483 ; 10459219 (ISSN) Imani, N ; Sarbazi-Azad, H ; Zomaya, A.Y ; Moinzadeh, P ; Sharif University of Technology
    2009
    Abstract
    In this paper, we consider the problem of searching a network for intruders. We propose a strategy for capturing the intruder in the popular interconnection topology, the star network. According to the proposed strategy, a team of collaborative software agents are responsible for capturing a hostile intruder (e.g. a virus). These agents asynchronously move along the network links and the intruder has the capability of escaping arbitrarily fast. © 2009 IEEE  

    Resource placement in three-dimensional tori

    , Article Parallel Computing ; Volume 35, Issue 10-11 , 2009 , Pages 535-543 ; 01678191 (ISSN) Mahini, H ; Sarbazi Azad, H ; Sharif University of Technology
    2009
    Abstract
    In massively parallel processing systems that incorporate hundreds and thousands of processing nodes, the problem of placing a limited number of resources (e.g. printers, disks, software copies, etc.) over processing nodes is of great importance. In this paper, we investigate resource placement in the three-dimensional torus network which is the underlying interconnection network in most current multicomputer. We show that there exists an irregular distance-1 placement only for tori of the form 2 × 3 i × 6 j, i, j ∈ N. In addition, we present a new formal proof for the necessary and sufficient conditions for the existence of irregular distance-d placement in 3D tori. © 2009 Elsevier B.V. All... 

    Exploitation of wavelength, hardware, and path redundancies in fault-tolerant all-optical DCNs

    , Article Optical Fiber Technology ; Volume 51 , 2019 , Pages 77-89 ; 10685200 (ISSN) Akbari Rokn Abadi, S ; Koohi, S ; Sharif University of Technology
    Academic Press Inc  2019
    Abstract
    Data center performance is affected by three main factors; bandwidth, latency, and reliability of intra-data center interconnection network. Bandwidth and latency are definitely improved by adopting optical technology for intra-data center communication, but fault tolerance of the corresponding optical networks has been raised less. Recently, we introduced two Torus-based, all-optical, and non-blocking networks, i.e. O-TF and O-FTF, addressing reliability of optical networks, and now, in this paper, to address the scalability problem, we propose a novel Optical Clos-based architecture which reduces minimum number of required wavelength channels, as well as, the switch size in each node....