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13
Fast Concurrent Access to Parallel Disks
 In 11th ACMSIAM Symposium on Discrete Algorithms
, 1999
"... High performance applications involving large data sets require the efficient and flexible use of multiple disks. In an external memory machine with D parallel, independent disks, only one block can be accessed on each disk in one I/O step. This restriction leads to a load balancing problem that is ..."
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Cited by 52 (11 self)
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High performance applications involving large data sets require the efficient and flexible use of multiple disks. In an external memory machine with D parallel, independent disks, only one block can be accessed on each disk in one I/O step. This restriction leads to a load balancing problem that is perhaps the main inhibitor for adapting singledisk external memory algorithms to multiple disks. This paper shows that this problem can be solved efficiently using a combination of randomized placement, redundancy and an optimal scheduling algorithm. A buffer of O(D) blocks suffices to support efficient writing of arbitrary blocks if blocks are distributed uniformly at random to the disks (e.g., by hashing). If two randomly allocated copies of each block exist, N arbitrary blocks can be read within dN=De + 1 I/O steps with high probability. In addition, the redundancy can be reduced from 2 to 1 + 1=r for any integer r. These results can be used to emulate the simple and powerful "singledisk multihead" model of external computing [1] on the physically more realistic independent disk model [33] with small constant overhead. This is faster than a lower bound for deterministic emulation [3].
Interpreting Stale Load Information
 IEEE Transactions on parallel and distributed systems
, 1999
"... In this paper we examine the problem of balancing load in a largescale distributed system when information about server loads may be stale. It is well known that sending each request to the machine with the apparent lowest load can behave badly in such systems, yet this technique is common in pr ..."
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Cited by 41 (0 self)
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In this paper we examine the problem of balancing load in a largescale distributed system when information about server loads may be stale. It is well known that sending each request to the machine with the apparent lowest load can behave badly in such systems, yet this technique is common in practice. Other systems use roundrobin or random selection algorithms that entirely ignore load information or that only use a small subset of the load information. Rather than risk extremely bad performance on one hand or ignore the chance to use load information to improve performance on the other, we develop strategies that interpret load information based on its age. Through simulation, we examine several simple algorithms that use such load interpretation strategies under a range of workloads. Our experiments suggest that by properly interpreting load information, systems can (1) match the performance of the most aggressive algorithms when load information is fresh relative to the...
On Contention Resolution Protocols and Associated Probabilistic Phenomena
 IN PROCEEDINGS OF THE 26TH ANNUAL ACM SYMPOSIUM ON THEORY OF COMPUTING
, 1994
"... ..."
Packet Routing In FixedConnection Networks: A Survey
, 1998
"... We survey routing problems on fixedconnection networks. We consider many aspects of the routing problem and provide known theoretical results for various communication models. We focus on (partial) permutation, krelation routing, routing to random destinations, dynamic routing, isotonic routing ..."
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Cited by 29 (3 self)
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We survey routing problems on fixedconnection networks. We consider many aspects of the routing problem and provide known theoretical results for various communication models. We focus on (partial) permutation, krelation routing, routing to random destinations, dynamic routing, isotonic routing, fault tolerant routing, and related sorting results. We also provide a list of unsolved problems and numerous references.
Practical load balancing for content requests in peertopeer networks
"... This paper studies the problem of balancing the demand for content in a peertopeer network across heterogeneous peer nodes that hold replicas of the content. Previous decentralized load balancing techniques in distributed systems base their decisions on periodic updates containing information ab ..."
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Cited by 15 (1 self)
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This paper studies the problem of balancing the demand for content in a peertopeer network across heterogeneous peer nodes that hold replicas of the content. Previous decentralized load balancing techniques in distributed systems base their decisions on periodic updates containing information about load or available capacity observed at the serving entities. We show that these techniques do not work well in the peertopeer context; either they do not address peer node heterogeneity, or they suffer from significant load oscillations which result in unutilized capacity. We propose a new decentralized algorithm, MaxCap, based on the maximum inherent capacities of the replica nodes. We show that unlike previous algorithms, it is not tied to the timeliness or frequency of updates, and consequently requires significantly less update overhead. Yet, MaxCap can handle the heterogeneity of a peertopeer environment without suffering from load oscillations.
Simulating shared memory in real time: On the computation power of reconfigurable meshes
 in ``Proceedings of the 2nd IEEE Workshop on Reconfigurable Architectures
, 1995
"... We consider randomized simulations of shared memory on a distributed memory machine (DMM) where the n processors and the n memory modules of the DMM are connected via a reconfigurable architecture. We first present a randomized simulation of a CRCW PRAM on a reconfigurable DMM having a complete reco ..."
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Cited by 6 (1 self)
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We consider randomized simulations of shared memory on a distributed memory machine (DMM) where the n processors and the n memory modules of the DMM are connected via a reconfigurable architecture. We first present a randomized simulation of a CRCW PRAM on a reconfigurable DMM having a complete reconfigurable interconnection. It guarantees delay O(log *n), with high probability. Next we study a reconfigurable mesh DMM (RMDMM). Here the n processors and n modules are connected via an n_n reconfigurable mesh. It was already known that an n_m reconfigurable mesh can simulate in constant time an nprocessor CRCW PRAM with shared memory of size m. In this paper we present a randomized step by step simulation of a CRCW PRAM with arbitrarily large shared memory on an RMDMM. It guarantees constant delay with high probability, i.e., it simulates in real time. Finally we prove a lower bound showing that size 0(n 2) for the reconfigurable mesh is necessary for real time simulations.] 1997 Academic Press * Supported by DFGGraduiertenkolleg ``Parallele Rechnernetzwerke in der Produktionstechnik,''
CommunicationEfficient Bulk Synchronous Parallel Algorithms
, 2001
"... Communication has been pointed out to be the major bottleneck for the performance of parallel algorithms. Theoretical parallel models such as PRAM have long been questioned due to the fact that the theoretical algorithmic efficiency does not provide a satisfactory performance prediction when algorit ..."
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Communication has been pointed out to be the major bottleneck for the performance of parallel algorithms. Theoretical parallel models such as PRAM have long been questioned due to the fact that the theoretical algorithmic efficiency does not provide a satisfactory performance prediction when algorithms are implemented on commercially available parallel machines. This is mainly because these models do not provide a reasonable scheme for measuring the communication overhead. Recently several practical parallel models aiming at achieving portability and scalability of parallel algorithms have been widely discussed. Among them, the Bulk Synchronous Parallel (BSP) model has received much attention as a bridging model for parallel computation, as it generally better addresses practical concerns like communication and synchronization. The BSP model has been used in a number of application areas, primarily in scientific computing. Yet, very little work has been done on problems generally considered to be irregularly structured, which usually result in highly datadependent communication patterns and make it difficult to achieve communication efficiency. Typical examples are fundamental problems in graph theory and computational geometry, which are important as a vast number of interesting problems in many fields are defined in terms of v them. Thus practical and communicationefficient parallel algorithms for solving these problems are important. In this dissertation, we present scalable parallel algorithms for some fundamental problems in graph theory and computational geometry. In addition to the time complexity analysis, we also present some techniques for worstcase and averagecase communication complexity analyses. Experimental studies have been performed on two differ...
ETFA'2009 14th IEEE International Conference on Emerging Technologies and Factory Automation On the Use of Hash Tables in RealTime Applications
"... Abstract. Software applications use hash tables for many different purposes. Hash tables have an excellent averagecase behavior but, in the worstcase, it degrades to something like a chained list. Because of that, the use of hash tables in realtime systems is not usual, since those systems may be ..."
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Abstract. Software applications use hash tables for many different purposes. Hash tables have an excellent averagecase behavior but, in the worstcase, it degrades to something like a chained list. Because of that, the use of hash tables in realtime systems is not usual, since those systems may be required to guarantee deadlines. This paper discusses the use of hash table in realtime systems, considering that when the probability of an undesirable behavior is low enough, it can be ignored. It also compares approaches simple and 2choice for the table design. 1.