Presents a definition of a read-write register that sometimes returns out-of-date values, shows that the definition is implemented by the probabilistic quorum algorithm of D. Malkhi et al. (1997), and shows how to pro...
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ISBN:
(纸本)0769510779
Presents a definition of a read-write register that sometimes returns out-of-date values, shows that the definition is implemented by the probabilistic quorum algorithm of D. Malkhi et al. (1997), and shows how to program with such registers using the framework of A. U/spl uml/resin and M. Dubois (1990). Consequently, existing iterative algorithms for an interesting class of problems (including finding shortest paths, constraint satisfaction and transitive closure) converge with high probability if executed in a system in which the shared data is implemented with registers satisfying the new definition. Furthermore, the algorithms in this framework inherit positive attributes concerning load and availability from the underlying register implementation. A monotone version of the new register definition is specified and implemented; it can provide improved expected convergence time and message complexity for iterative algorithms.
In this paper, Petri Nets (PNs) are used for deriving efficient mapping transformations of a wide class of algorithms to processor arrays. In the proposed methodology, given an algorithm and the interconnections of th...
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In this paper, Petri Nets (PNs) are used for deriving efficient mapping transformations of a wide class of algorithms to processor arrays. In the proposed methodology, given an algorithm and the interconnections of the processor array, two PNs are constructed: one that is related to the algorithm and one that is related to the processor array. The former PN models the execution of the algorithm and differs drastically from the common data-flow methods. Based on properties of PNs and on the reachability tree analysis technique, a theorem is given, through which the two PN model suggest all possible ways of implementing the algorithm by the processor array.< >
A class of hybrid domain-iterative algorithms for 2-D image reconstruction is described. The consistent iterative reconstruction-reprojection (CIRR) algorithm was designed and implemented along with other classical do...
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A class of hybrid domain-iterative algorithms for 2-D image reconstruction is described. The consistent iterative reconstruction-reprojection (CIRR) algorithm was designed and implemented along with other classical domain-iterative methods. The algorithms are tested on the hollow projections problem, where simple object models are assumed known. Results show that the CIRR algorithm is robust and accurate, and converges quickly.< >
We present an iterative algorithm for restoring synthetic aperture radar (SAR) images with arbitrary gaps in spatial frequency. In some SAR applications a contiguous frequency band is not recorded which results in gap...
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We present an iterative algorithm for restoring synthetic aperture radar (SAR) images with arbitrary gaps in spatial frequency. In some SAR applications a contiguous frequency band is not recorded which results in gaps in the SAR image spectrum. These gaps manifest themselves as artifacts which degrade the quality of the associated SAR image. Maximum a posteriori (MAP) techniques allow one to compensate for these spectrum gaps but can result in a difficult high-dimensional optimization problem. By using concepts collectively known as optimization transfer or MM-algorithms, one can easily design efficient iterative algorithms that are tuned for a particular objective function and have provable convergence properties. In this paper we will review MAP-based SAR image restoration, derive an iterative algorithm that monotonically minimizes the associated objective function, and demonstrate it on actual SAR imagery.
An iterative algorithm can be modeled by a cyclic data-flow graph. The bottleneck for scheduling cyclic data-flow graphs lies on dependencies that form cycles. The maximum computation-time-to-delay ratio among all the...
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An iterative algorithm can be modeled by a cyclic data-flow graph. The bottleneck for scheduling cyclic data-flow graphs lies on dependencies that form cycles. The maximum computation-time-to-delay ratio among all the cycles in the graph, gives a lower bound on pipeline schedule length. In this paper, a framework for algebraic transformations is proposed to reduce the lower bound. A novel algorithm is proposed to apply transformations within iterations or over iteration boundaries. A set of beneficial transformations are chosen, and applied simultaneously in each pass of the algorithm. A measure of criticalness on loops is used to identify transformations leading to potential lower bound reduction. Experimental results show that substantial reductions on the lower bound are achieved, and shorter pipelined schedules are generated.
This paper presents many typical problems that are encountered when executing large scale scientific applications over distributed architectures. The causes and effects of these problems are explained and a solution f...
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This paper presents many typical problems that are encountered when executing large scale scientific applications over distributed architectures. The causes and effects of these problems are explained and a solution for some classes of scientific applications is also proposed. This solution is the combination of the asynchronous iteration model with JACEP2P-V2 which is a fully decentralized and fault tolerant platform dedicated to executing parallel asynchronous applications over volatile distributed architectures. We explain in detail how our approach deals with each of these problems. Then we present two large scale numerical experiments that prove the efficiency and the robustness of our approach.
The paper analyses and compares alternative iterative and recursive implementations of FPGA circuits for various problems. Two types of recursive calls have been examined, namely for cyclic and binary (N-ary) search a...
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The paper analyses and compares alternative iterative and recursive implementations of FPGA circuits for various problems. Two types of recursive calls have been examined, namely for cyclic and binary (N-ary) search algorithms. The details of experiments are presented for four different design problems. The relevant comparative data have been obtained as a result of synthesis and implementation in FPGAs of the respective circuits from system-level (Handel-C) and RTL (VHDL) specifications.
This paper focuses on the identification problem for finite impulse response systems through using the hierarchical identification principle. Based on the hierarchical identification principle, the hierarchical based ...
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ISBN:
(数字)9781728159225
ISBN:
(纸本)9781728159232
This paper focuses on the identification problem for finite impulse response systems through using the hierarchical identification principle. Based on the hierarchical identification principle, the hierarchical based least squares iterative algorithm is proposed to estimate the parameters of the two-input single-output Hammerstein finite impulse response systems. Finally, a simulation example is given to test the effectiveness of the proposed algorithm.
The implementation of parallel asynchronous iterative algorithms on message passing architectures is considered. Several issues related to communication via message passing interfaces or libraries such as MPI-1, MPI-2...
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The implementation of parallel asynchronous iterative algorithms on message passing architectures is considered. Several issues related to communication via message passing interfaces or libraries such as MPI-1, MPI-2, PVM or SHMEM are discussed in this survey paper. Practical implementations are proposed
We introduce a general iterative scheme for image reconstruction based on Landweber's method. Within our configuration, the block-iterative (BI) version can be formulated from its simultaneous version easily, and ...
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ISBN:
(纸本)078037584X
We introduce a general iterative scheme for image reconstruction based on Landweber's method. Within our configuration, the block-iterative (BI) version can be formulated from its simultaneous version easily, and vice versa. This provides the mechanism to formulate new algorithms from known algorithms. It can be shown that some of the widely used iterative algorithms, such as the ART, SART, Cimmino's Algorithm and recently designed DWE and CAV, are special examples of the general scheme or its BI version. By applying the convergence results of the general scheme, the corresponding convergence in the consistent or inconsistent cases, for the block-iterative or simultaneous versions, of those specific algorithms can be established under mild conditions on the relaxation parameters.
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