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Three non Conventional Paradigms of Parallel Computation
, 1992
"... . We consider three paradigms of computation where the benefits of a parallel solution are greater than usual. Paradigm 1 works on a timevarying input data set, whose size increases with time. In paradigm 2 the data set is fixed, but the processors may fail at any time with a given constant probabi ..."
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Cited by 14 (0 self)
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. We consider three paradigms of computation where the benefits of a parallel solution are greater than usual. Paradigm 1 works on a timevarying input data set, whose size increases with time. In paradigm 2 the data set is fixed, but the processors may fail at any time with a given constant probability. In paradigm 3, the execution of a single operation may require more than one processor, for security or reliability reasons. We discuss the organization of PRAM algorithms for these paradigms, and prove new bounds on parallel speedup. 1 Introduction The theory of parallel algorithms has a well known body, developed on the PRAM model [5]. Some folklore principles are at the base of this theory, in particular the ones that express upper and lower bounds on the processing time. Let \Pi be a problem of size N , and let T s (N) be the time required by the best known sequential algorithm A s to solve \Pi . Any parallel algorithm A p that solves \Pi with a number P of PRAM processors...
Performing tasks on restartable messagepassing processors
 in Proc. of the 11th Intl Workshop on Distr. Alg. (WDAG’97
, 1997
"... Abstract. This work presents new algorithms for the "DoAll " problem that consists of performing t tasks reliably in a messagepassing synchronous system of p faultprone processors. The algorithms are based on an aggressive coordination paradigm in which multiple coordinators may be active as the ..."
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Abstract. This work presents new algorithms for the "DoAll " problem that consists of performing t tasks reliably in a messagepassing synchronous system of p faultprone processors. The algorithms are based on an aggressive coordination paradigm in which multiple coordinators may be active as the result of failures. The first algorithm is tolerant of f < p stopfailures and it does not allow restarts. It has the available processor steps complexity S = O((t + plogp/loglogp), log f) and the message complexity M = O(t + plogp/loglogp + f • p). Unlike prior solutions, our algorithm uses redundant broadcasts when encountering failures and, for large f, it has better S complexity. This algorithm is used as the basis for another algorithm which tolerates any pattern of stopfailures and restarts. This new algorithm is the first solution for the DoAll problem that efficiently deals with processor restarts. Its available processor steps complexity is S = O((t + p log p + f). rain{log p, log f}), and its message complexity is M = O(t +p. logp + f.p), where f is the number of failures. 1
Online Scheduling of Parallel Programs on Heterogeneous Systems with Applications to Cilk
 Theory of Computing Systems Special Issue on SPAA
, 2002
"... We study the problem of executing parallel programs, in particular Cilk programs, on a collection of processors of di erent speeds. We consider a model in which each processor maintains an estimate of its own speed, where communication between processors has a cost, and where all scheduling must be ..."
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Cited by 13 (2 self)
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We study the problem of executing parallel programs, in particular Cilk programs, on a collection of processors of di erent speeds. We consider a model in which each processor maintains an estimate of its own speed, where communication between processors has a cost, and where all scheduling must be online. This problem has been considered previously in the fields of asynchronous parallel computing and scheduling theory. Our model is a bridge between the assumptions in these fields. We provide a new more accurate analysis of an old scheduling algorithm called the maximum utilization scheduler. Based on this analysis, we generalize this scheduling policy and define the high utilization scheduler. We next focus on the Cilk platform and introduce a new algorithm for scheduling Cilk multithreaded parallel programs on heterogeneous processors. This scheduler is inspired by the high utilization scheduler and is modified to fit in a Cilk context. A crucial aspect of our algorithm is that it keeps the original spirit of the Cilk scheduler. In fact, when our new algorithm runs on homogeneous processors, it exactly mimics the dynamics of the original Cilk scheduler.
Performing Tasks on Synchronous Restartable MessagePassing Processors
 Distributed Computing
, 2000
"... We consider the problem of performing t tasks in a distributed system of p faultprone processors. This problem, called doall herein, was introduced by Dwork, Halpern and Waarts. Our work deals with a synchronous messagepassing distributed system with processor stopfailures and restarts. We presen ..."
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Cited by 13 (3 self)
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We consider the problem of performing t tasks in a distributed system of p faultprone processors. This problem, called doall herein, was introduced by Dwork, Halpern and Waarts. Our work deals with a synchronous messagepassing distributed system with processor stopfailures and restarts. We present two new algorithms based on a new aggressive coordination paradigm by which multiple coordinators may be active as the result of failures. The first algorithm is tolerant of f < p stopfailures and it does not allow restarts. It has available processor steps (work) complexity S = O((t + p log p= log log p) log f) and message complexity M = O(t + p log p= log log p + fp). Unlike prior solutions, our algorithm uses redundant broadcasts when encountering failures and, for p = t and large f , it achieves better work complexity. This algorithm is used as the basis for another algorithm that tolerates stopfailures and restarts. This new algorithm is the first solution for the doall problem that efficiently deals with processor restarts. Its available processor steps complexity is S = O((t + p log p + f) minflog p; log fg), and its message complexity is M = O(t+p log p+fp), where f is the total number of failures.
Metacomputing with MILAN
 In Proceeding of the 8 th Heterogeneous Computing Workshop
, 1999
"... The MILAN project, a joint effort involving Arizona State University and NewYork University, has produced and validated fundamental techniques for the realization of efficient, reliable, predictable virtual machines on top of metacomputing environments that consist of an unreliable and dynamically c ..."
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Cited by 12 (2 self)
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The MILAN project, a joint effort involving Arizona State University and NewYork University, has produced and validated fundamental techniques for the realization of efficient, reliable, predictable virtual machines on top of metacomputing environments that consist of an unreliable and dynamically changing set of machines. In addition to the techniques, the principal outcomes of the project include three parallel programming systemsCalypso, Chime, and Charlotte which enable applications be developed for ideal, shared memory, parallel machines to execute on distributed platforms that are subject to failures, slowdowns, and changing resource availability. The lessons learnt from the MILAN project are being used to design Computing Communities, a metacomputing framework for general computations. 1. Motivation MILAN (Metacomputing In Large Asynchronous Networks) is a joint project of Arizona State University and NewYork University. The primary objective of the MILAN project is to p...
Structural Parallel Algorithmics
, 1991
"... The first half of the paper is a general introduction which emphasizes the central role that the PRAM model of parallel computation plays in algorithmic studies for parallel computers. Some of the collective knowledgebase on nonnumerical parallel algorithms can be characterized in a structural way ..."
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Cited by 11 (4 self)
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The first half of the paper is a general introduction which emphasizes the central role that the PRAM model of parallel computation plays in algorithmic studies for parallel computers. Some of the collective knowledgebase on nonnumerical parallel algorithms can be characterized in a structural way. Each structure relates a few problems and technique to one another from the basic to the more involved. The second half of the paper provides a bird'seye view of such structures for: (1) list, tree and graph parallel algorithms; (2) very fast deterministic parallel algorithms; and (3) very fast randomized parallel algorithms. 1 Introduction Parallelism is a concern that is missing from "traditional" algorithmic design. Unfortunately, it turns out that most efficient serial algorithms become rather inefficient parallel algorithms. The experience is that the design of parallel algorithms requires new paradigms and techniques, offering an exciting intellectual challenge. We note that it had...
Efficient Execution of Nondeterministic Parallel Programs on Asynchronous Systems
, 1996
"... We consider the problem of asynchronous execution of parallel programs. We assume that the original program is designed for a synchronous system, whereas the actual system may be asynchronous. We seek an automatic execution scheme, which allows the asynchronous system to execute the synchronous prog ..."
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Cited by 11 (6 self)
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We consider the problem of asynchronous execution of parallel programs. We assume that the original program is designed for a synchronous system, whereas the actual system may be asynchronous. We seek an automatic execution scheme, which allows the asynchronous system to execute the synchronous program. Previous execution schemes provide solutions only for the case where the original program is deterministic. Here, we provide the first solution for the more general case where the original program can be nondeterministic (e.g. randomized). Our scheme is based on a novel agreement protocol for the asynchronous parallel setting. Our protocol allows n asynchronous processors to agree on n wordsized values in O(n log n log log n) total work. Total work is defined to be the summation of the number of steps performed by all processors (including steps from busy waiting). 1 Introduction Motivation. Parallel programs are frequently designed assuming tightlycoupled processors, operating in ...
Javelin: Parallel Computing on the Internet
 Future Generation Computer Systems
, 1999
"... Java offers the basic infrastructure needed to integrate computers connected to the Internet into a seamless distributed computational resource: an infrastructure for running coarsegrained parallel applications on numerous, anonymous machines. First, we sketch such a resource's essential technica ..."
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Cited by 11 (0 self)
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Java offers the basic infrastructure needed to integrate computers connected to the Internet into a seamless distributed computational resource: an infrastructure for running coarsegrained parallel applications on numerous, anonymous machines. First, we sketch such a resource's essential technical properties. Then, we present a prototype of Javelin, an infrastructure for global computing. The system is based on Internet software that is interoperable, increasingly secure, and ubiquitous: Javaenabled Web technology. Ease of participation is seen as a key property for such a resource to realize the vision of a multiprocessing environment comprising thousands of computers. Javelin's architecture and implementation require participants to have access to only a Javaenabled Web browser. Experimental results are given in the form of a Mersenne Prime application and a raytracing application that run on a heterogeneous network of several parallel machines, workstations, and PCs. Tw...
Exploiting Application Tunability for Efficient, Predictable Resource Management in Parallel and Distributed Systems
 In Proc. 13th Intl. Parallel Processing Symposium
, 1999
"... this paper, we propose a novel approach ..."
The Complexity of Synchronous Iterative DoAll with Crashes
, 2001
"... DoAll is the problem of performing N tasks in a distributed system of P failureprone processors [9]. Many distributed and parallel algorithms have been developed for this basic problem and several algorithm simulations have been developed by iterating DoAll algorithms. The eciency of the solut ..."
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Cited by 10 (2 self)
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DoAll is the problem of performing N tasks in a distributed system of P failureprone processors [9]. Many distributed and parallel algorithms have been developed for this basic problem and several algorithm simulations have been developed by iterating DoAll algorithms. The eciency of the solutions for DoAll is measured in terms of work complexity where all processing steps taken by the processors are counted. Work is ideally expressed as a function of N , P , and f , the number of processor crashes. However the known lower bounds and the upper bounds for extant algorithms do not adequately show how work depends on f . We present the rst nontrivial lower bounds for DoAll that capture the dependence of work on N , P and f . For the model of computation where processors are able to make perfect loadbalancing decisions locally, we also present matching upper bounds. Thus we give the rst complete analysis of DoAll for this model. We dene the riterative DoAll problem that abstracts the repeated use of DoAll such as found in algorithm simulations. Our fsensitive analysis enables us to derive a tight bound for riterative DoAll work (that is stronger than the rfold work complexity of a single DoAll). Our approach that models perfect loadbalancing allows for the analysis of specic algorithms to be divided into two parts: (i) the analysis of the cost of tolerating failures while performing work, and (ii) the analysis of the cost of implementing loadbalancing. We demonstrate the utility and generality of this approach by improving the analysis of two known ecient algorithms. We give an improved analysis of an ecient messagepassing algorithm (algorithm AN [5]). We also derive a new and complete analysis of the best known DoAll algorithm for...