February 2001

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35 Reads

Published by Elsevier BV

Print ISSN: 0020-0190

February 2001

·

35 Reads

An error-comprising workflow definition might provoke serious
problems to an enterprise, especially when it is involved with mission
critical business processes. Concurrency of workflow processes is known
as one of the major sources causing such an invalid workflow process
definition. So, the conflicts caused by concurrent workflow processes
should be considered deliberately when defining concurrent workflow
processes. However, it is very difficult to ascertain whether a workflow
process is free from conflicts or not without any experimental
executions at runtime; this would be very tedious and time consuming
work for process designers. If we can analyze the conflicts immanent in
concurrent workflow definition prior to runtime, it would be very
helpful to business process designers and many other users of workflow
management systems. The authors propose a set-based constraint system to
analyze possible read-write conflicts and write-write conflicts between
activities which read and write to the shared variables in a workflow
process definition. The system is composed of two phases. In the first
phase, it generates set constraints from a structured workflow
definition. In the second phase, it finds the minimal solution of the
set constraints

April 1992

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172 Reads

The authors show that high-resolution images can be encoded and decoded efficiently in parallel. They present an algorithm based on the hierarchical multi-level progressive (MLP) method, used either with Huffman coding or with a new variant of arithmetic coding called quasi-arithmetic coding. The coding step can be parallelized, even though the codes for different pixels are of different lengths; parallelization of the prediction and error modeling components is straightforward.< >

January 1991

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23 Reads

Schnorr and Shamir and independently Kunde, have shown that
sorting N = n <sup>2</sup> inputs into snake-like
ordering on a n × n mesh requires
3 n - o ( n ) steps. Using a less restrictive, more
realistic model the author shows that the sorting N = n
<sup>2</sup> integers in the range [1. . . N ] can be performed
in 2 n + o ( n ) steps on a n × n
mesh

February 2000

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36 Reads

We consider two general precedence-constrained scheduling problems that have wide applicability in the areas of parallel processing, high performance compiling, and digital system synthesis. These problems are intractable so it is important to be able to compute tight bounds on their solutions. A tight lower bound on makespan scheduling can be obtained by replacing precedence constraints with release and due dates, giving a problem that can be efficiently solved. We demonstrate that recursively applying this approach yields a bound that is provably tighter than other known bounds, and experimentally shown to achieve the optimal value at least 86.5% of the time over a synthetic benchmark. We compute the best known lower bound on weighted completion time scheduling by applying the recent discovery of a new algorithm for solving a related scheduling problem. Experiments show that this bound significantly outperforms the linear programming-based bound. We have therefore demonstrated that combinatorial algorithms can be a valuable alternative to linear programming for computing tight bounds on large scheduling problems

July 1990

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22 Reads

A multilayer feedforward neural network is proposed to solve
sorting problems. The network has O(n<sup>2</sup>) neurons and O(n<sup>2
</sup>) links. The number of layers is fixed regardless of input size.
Thus, the computation time of the network is independent of input size,
and the sorting network has a time complexity of O(1)

November 2002

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19 Reads

An effective way to process subsequence matching in time-series databases was proposed. An R*-tree was constructed on query window points, for effective processing of the window-join. The proposed method accessed each R*-tree page built on data windows exactly once without incurring any index-level false alarms. Therefore, in terms of the number of disk accesses, the method proved to be optimal. Performance evaluation through extensive experiments showed the superiority of the proposed method over the previous one.

February 2002

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11 Reads

We consider strongly-connected, directed networks of identical synchronous, finite-state processors with in- and out-degree uniformly bounded by a network constant. Via a straightforward extension of R. Ostrovsky and D. Wilkerson's backwards communication algorithm (1995), we exhibit a protocol which solves the global topology determination problem, the problem of having a root processor map the global topology of a network of. unknown size and topology, with running time O(ND) where N represents the number of processors and D represents the diameter of the network. A simple counting argument suffices to show that the global topology determination problem has time-complexity Ω(N log N) which makes the protocol presented asymptotically time-optimal for many large networks

June 2003

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90 Reads

In this paper the analysis of packet loss for Gilbert-model with loss rate feedback is performed. Based on the historical loss rate feedbacks, an iterative algorithm can be derived to compute the conditional version of P(m, n), and which is the probability of m lost packets within a block of n packets. Experimental simulations validate the analytical results, and they are helpful for any joint source-channel coding system for which FEC protection with loss rate feedback is suitable.

February 2000

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20 Reads

An increasing proportion of the effort of skilled programmers is devoted to servicing the legacy of software. The techniques and tools currently in use to tackle the problem take good advantage of the results of past research into programming theory. I suggest that new generations of tools will be based on concepts and principles developed by basic research of the present and by future research directed at currently outstanding challenges. These points are illustrated by examples drawn from my personal experience. They show that academic research and education can contribute to industrial development and production in an atmosphere of mutual respect for their different allegiances and timescales, and in recognition of convergence of their long-term goals.

August 1990

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28 Reads

The existence of an oracle A such that ⊕P<sup>A
</sup> is not contained in PP<sup>PHA</sup> is proved. This separation
follows in a straightforward manner from a circuit complexity result,
which is also proved: to compute the parity of n inputs, any
constant depth circuit consisting of a single threshold gate on top of
ANDs and ORs requires exponential size in n

February 1991

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6 Reads

Two sequences of items sorted in increasing order are given: a sequence A of size n and a sequence B of size m . It is required to determine, for every item of A , the smallest item of B (if one exists) that is larger than it. The paper presents two parallel algorithms for the problem. The first algorithm requires O(log m +log n ) time using n processors on an EREW PRAM. On an EREW PRAM with p ( p ⩽min{ m , n }) processors, the second algorithm runs in O(log n +<sub>p</sub>/<sup>n</sup>) time when m ⩽ n , or in O(log m +<sub>p</sub>/<sup>n </sup>log<sub>n</sub>/<sup>2m</sup>) time when m > n . The second algorithm is optimal

July 2008

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60 Reads

In 1996, Jakobsson, Sako, and Impagliazzo and, on the other hand, Chaum introduced the notion of designated verifier signatures to solve some of the intrinsic problems of undeniable signatures. The generalization of this concept was formally investigated by Laguillaumie and Vergnaud as multi-designated verifiers signatures. Recently, Laguillaumie and Vergnaud proposed the first multi-designated verifiers signature scheme which protects the anonymity of signers without encryption. In this paper, we show that their scheme is insecure against rogue-key attacks.

September 2009

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28 Reads

The input of the Edge Multicut problem consists of an undirected graph G and pairs of terminals {s1,t1},…,{sm,tm}; the task is to remove a minimum set of edges such that si and ti are disconnected for every 1⩽i⩽m. The parameterized complexity of the problem, parameterized by the maximum number k of edges that are allowed to be removed, is currently open. The main result of the paper is a parameterized 2-approximation algorithm: in time f(k)⋅nO(1), we can either find a solution of size 2k or correctly conclude that there is no solution of size k.The proposed algorithm is based on a transformation of the Edge Multicut problem into a variant of the parameterized Max-2SAT problem, where the parameter is related to the number of clauses that are not satisfied. It follows from previous results that the latter problem can be 2-approximated in a fixed-parameter time; on the other hand, we show here that it is W[1]-hard. Thus the additional contribution of the present paper is introducing the first natural W[1]-hard problem that is constant-ratio fixed-parameter approximable.

August 2009

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206 Reads

We present an algorithm to find a Hamiltonian cycle in a proper interval graph in O(m+n) time, where m is the number of edges and n is the number of vertices in the graph. The algorithm is simpler and shorter than previous algorithms for the problem.

April 2009

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64 Reads

We consider the conjectured O(N2+ϵ) time complexity of multiplying any two N×N matrices A and B. Our main result is a deterministic Compressed Sensing (CS) algorithm that both rapidly and accurately computes A⋅B provided that the resulting matrix product is sparse/compressible. As a consequence of our main result we increase the class of matrices A, for any given N×N matrix B, which allows the exact computation of A⋅B to be carried out using the conjectured O(N2+ϵ) operations. Additionally, in the process of developing our matrix multiplication procedure, we present a modified version of Indyk's recently proposed extractor-based CS algorithm [P. Indyk, Explicit constructions for compressed sensing of sparse signals, in: SODA, 2008] which is resilient to noise.

February 2009

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48 Reads

In this paper the minmax (regret) versions of some basic polynomially solvable deterministic network problems are discussed. It is shown that if the number of scenarios is unbounded, then the problems under consideration are not approximable within log1−ϵK for any ϵ>0 unless NP⊆DTIME(npolylogn), where K is the number of scenarios.

July 2013

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41 Reads

Morpion Solitaire is a pencil-and-paper game for a single player. A move in
this game consists of putting a cross at a lattice point and then drawing a
line segment that passes through exactly five consecutive crosses. The
objective is to make as many moves as possible, starting from a standard
initial configuration of crosses. For one of the variants of this game, called
5D, we prove an upper bound of 121 on the number of moves. This is done by
introducing line-based analysis, and improves the known upper bound of 138
obtained by potential-based analysis.

March 1988

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216 Reads

We present a new implementation of the Kou, Markowsky and Berman algorithm for finding a Steiner tree for a connected, undirected distance graph with a specified subset S of the set of vertices V. The total distance of all edges of this Steiner tree is at most 2(1-1/l) times that of a Steiner minimal tree, where l is the minimum number of leaves in any Steiner minimal tree for the given graph. The algorithm runs in O(|E|+|V|log|V|) time in the worst case, where E is the set of all edges and V the set of all vertices in the graph.

February 2002

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44 Reads

In this paper we demonstrate a fast correlation attack on the recently proposed stream cipher LILI-128. The attack has complexity around 271 bit operations assuming a received sequence of length around 230 bits and a precomputation phase of complexity 279 table lookups. This complexity is significantly lower than 2112, which was conjectured by the inventors of LILI-128 to be a lower bound on the complexity of any attack.

June 2002

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22 Reads

To prove a block cipher is secure against Differential Cryptanalysis one should show the maximum differential probability is a small enough value. We will prove that the maximum differential probability of a 13 round Skipjack-like structure is bounded by p4, where p is the maximum differential probability of round function.

March 1998

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64 Reads

A set of items has to be assigned to a set of bins with size one. If necessary, the size of the bins can be extended. The objective is to minimize the total size, i.e., the sum of the sizes of the bins. The Longest Processing Time heuristic is applied to this NP-hard problem. For this approximation algorithm we prove a worst-case bound of which is shown to be tight when the number of bins is even.

November 1995

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137 Reads

In this paper we present an attack upon the Needham-Schroeder public-key authentication protocol. The attack allows an intruder to impersonate another agent.

December 2014

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16 Reads

In 2012 B\'ona showed the rather surprising fact that the cumulative number
of occurrences of the classical patterns $231$ and $213$ are the same on the
set of permutations avoiding $132$, beside the pattern based statistics $231$
and $213$ do not have the same distribution on this set. Here we show that if
it is required for the symbols playing the role of $1$ and $3$ in the
occurrences of $231$ and $213$ to be adjacent, then the obtained statistics are
equidistributed on the set of $132$-avoiding permutations. Actually, expressed
in terms of vincular patterns, we prove the following more general results: the
statistics based on the patterns $b-ca$, $b-ac$ and $ba-c$, together with other
statistics, have the same joint distribution on $S_n(132)$, and so do the
patterns $bc-a$ and $c-ab$; and up to trivial transformations, these statistics
are the only based on length three proper (not classical nor adjacent) vincular
patterns which are equidistributed on a set of permutations avoiding a
classical length three pattern.

August 1983

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334 Reads

Let S denote a set of N records whose keys are distinct nonnegative integers less than some initially specified bound M. This paper introduces a new data structure, called the y-fast trie, which uses Θ(N) space and Θ(log log M) time for range queries on a random access machine. We will also define a simpler but less efficient structure, called the x-fast trie.

November 1995

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20 Reads

We present here a new model of computation: the Self-Modifying Finite Automaton (SMFA). This is similar to a standard finite automaton, but changes to the machine are allowed during a computation. It is shown here that a weak form of this model has the power to recognize an important class of context-free languages, the metalinear languages, as well as some significant non-context-free languages. Less restricted forms of SMFAs accept even more.