We consider the problem of finding an optimal order of computing a matrix-chain product. This problem can be solved using dynamic programming in O(n(3)) sequential time, but the best sequential algorithm known for thi...
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We consider the problem of finding an optimal order of computing a matrix-chain product. This problem can be solved using dynamic programming in O(n(3)) sequential time, but the best sequential algorithm known for this problem runs in O(n log n) time. A general technique for parallelizing a class of dynamic-programming algorithms leads to an algorithm that runs in O (n(6)/log n) time on a concurrent-read exclusive-write parallel random-access machine (CREW PRAM) with O (n(6)/log n) processors. The best parallel algorithm previously known runs in O(log(3) n) time using O(n(2)/log(3) n) processors. We present an algorithm that runs in O(log(4) n) time on a CREW PRAM with n processors.
More real systems have many components and their simulation requires significant execution times. The practical needs have conducted to distributed simulation rather than sequential method. Asynchronous parallel discr...
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The context of this study is the 3D reconstruction of urban scenes from aerial images. We intend to estimate a dense depth map precise enough to be exploited by recognition algorithms. In this paper, we show how a mul...
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ISBN:
(纸本)0819429597
The context of this study is the 3D reconstruction of urban scenes from aerial images. We intend to estimate a dense depth map precise enough to be exploited by recognition algorithms. In this paper, we show how a multi-view approach made up of very simple and automatic operations can achieve this goal. Unlike 2-view stereovision methods, we do not exploit a disparity map for depth estimation. The proposed method consists in directly scanning depth. For each depth hypothesis, a reference image is projected by using a planar perspective transformation. The correct hypothesis is found pixel by pixel by minimizing a simple matching criterion based on a gray level comparison. We calculate this criterion for each pixel of the reference image, each depth hypothesis and each baseline formed with the reference image and an other image of the sequence. The estimated depth map obtained with a synthetic aerial image sequence, shows that exploiting several images with different baselines reduces the reconstruction errors due to noise and false matches. We have implemented an algorithm composed of simple automatic computations, that should be highly parallelisable.
Different methods for revising propositional knowledge base have been proposed recently by several researchers, but all methods are intractable in the general case. For practical application, this paper presents a rev...
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Different methods for revising propositional knowledge base have been proposed recently by several researchers, but all methods are intractable in the general case. For practical application, this paper presents a revision method in special case, and gives a corresponding polynomial algorithm as well as its parallel version on CREW PRAM.
This paper presents parallel incremental algorithms for analyzing activity networks. The start-over algorithm used for this problem is a modified version of an algorithm due to Chaudhuri and Ghosh (BIT26(1986), 418-42...
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This paper presents parallel incremental algorithms for analyzing activity networks. The start-over algorithm used for this problem is a modified version of an algorithm due to Chaudhuri and Ghosh (BIT26(1986), 418-429). The computational model used is a shared memory single-instruction stream, multiple-data stream computer that allows both read and write conflicts. It is shown that the incremental algorithms for the event and activity insertion problems both require onlyO(loglogn) parallel time, in contrast toO(lognlog logn) parallel time for the corresponding start-over algorithm.
A formula is read-once if each variable appears in it at most once. An arithmetic formula is one in which the operations are addition, subtraction, multiplication, and division (and constants are allowed). We present ...
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A formula is read-once if each variable appears in it at most once. An arithmetic formula is one in which the operations are addition, subtraction, multiplication, and division (and constants are allowed). We present a randomized (Las Vegas) parallel algorithm for the exact interpolation of arithmetic read-once formulas over sufficiently large fields. More specifically, for n-variable read-once formulas and fields of size at least 3(n(2) + 3n - 2), our algorithm runs in O(log(2) n) parallel steps using O(n(4)) processors (where the field operations are charged unit cost). This complements some results from [N.H. Bshouty and R. Cleve, Proc. 33rd Annual Symposium on the Foundations of Computer Science, IEEE Computer Science Press, Los Alamitos, CA, 1992, pp. 24-27] which imply that other classes of read-once formulas cannot be interpolated-or even learned with membership and equivalence queries-in polylogarithmic time with polynomially many processors (even though they can be learned sequentially in polynomial time). These classes include boolean read-once formulas and arithmetic read-once formulas over fields of size o(n/log n) (for n variable read-once formulas).
For unrooted and cyclically ordered trees (CO-tree), the distance based on the ancestor-descendant relation-preserving mapping (TD), the distance based on the structure-preserving mapping (SPD), and the distance based...
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In this paper, we present a parallel recognition algorithm for bipartite-permutation graphs. The algorithm can be executed in O(log n) time on the CRCW PRAM if O(n(3)/log n) processors are used, or O(log(2)n) time on ...
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In this paper, we present a parallel recognition algorithm for bipartite-permutation graphs. The algorithm can be executed in O(log n) time on the CRCW PRAM if O(n(3)/log n) processors are used, or O(log(2)n) time on the CREW PRAM if O(n(3)/log(2)n) processors are used. Previously, Chen and Yesha have presented another CRCW PRAM algorithm that takes O(log n) time if O(n(3)) processors are used. Compared with Chen and Yesha's algorithm, our algorithm requires either less time and fewer processors on the same machine model, or fewer processors on a weaker machine model. Besides, our algorithm can be applied to determine if two bipartite-permutation graphs are isomorphic.
In this paper, simple optimal algorithms are presented for solving some problems related to interval graphs. These problems are the connected component problem, the spanning tree problem, the eccentricity problem, and...
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In this paper, simple optimal algorithms are presented for solving some problems related to interval graphs. These problems are the connected component problem, the spanning tree problem, the eccentricity problem, and the single source all destinations shortest path problem. All of the above four problems can be solved in linear time if the endpoints of the intervals are sorted. Moreover, our algorithms can be parallelized very easily so that the above problems can be solved in O(log n) time with O(n/log n) processors using the EREW PRAM model.
We present efficient algorithms for the nearest neighbor problem defined in an n × n binary image. We show that using a linear array with a reconfigurable pipelined bus system (LARPBS) of n2processors, the ne...
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We present efficient algorithms for the nearest neighbor problem defined in an n × n binary image. We show that using a linear array with a reconfigurable pipelined bus system (LARPBS) of n2processors, the nearest neighbor problem can be solved in O(loglogn) time, and using an LARPBS of n2+εprocessors, for any fixed constant ε>0. the nearest neighbor problem can be solved in O(l) time. We also show that the nearest neighbor problem can be solved on an LARPBS of n2processors in O(1) time with high probability.
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