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Industry is presently investigating the possibility to use commodity multicore processors connected by standard network components in safety critical systems like cars. In this scenario one clearly wants to be able to argue that a passenger on the rear seat trying to hack the car's entertainment system cannot shoot down the electronic chassis control and the engine control, although large portions...
In this paper we present a low cost fault-tolerant attitude determination system to a scientific satellite using COTS devices. We related our experience in developing the attitude determination system, where we combine proven fault tolerance techniques to protect the whole system composed only by COTS from the effects produced by transient faults. We detailed the failure cases and the detection, reconfiguration...
Complex motion makes consecutive frames experience dramatic change, and thus becomes a barrier to object-tracking. Three factors contribute to more complexity of motion: longer sampling period,an moving object with complex appearance and nonrestraint movement, occlusion, which causes mean shift algorithm losing its target due to too low a Bhattacharyya coefficient. To treat it, mean shift algorithm...
We describe a benchmark of publicly-available multi-threaded programs with documented bugs in them. This project was initiated a few years ago with the goal of helping research groups in the fields of concurrent testing and debugging to develop tools and algorithms that improve the quality of concurrent programs. We present a survey of usage of the benchmark, concluding that the benchmark had an impact...
A principal factor in sensor network design is energy efficiency. In this work, we propose to extend the lifetime of sensor networks using appropriate choice of sensor node distribution. The key idea of our scheme is to deploy more nodes in areas of extensive energy usage. Using this scheme of sensor node distribution, we use probabilistic angular routing to route data packets from the sensor nodes...
A new parallel algorithm for the maximal independent set problem (MIS) is constructed. It runs in O(log4 n) time when implemented on a linear number of EREW-processors. This is the first deterministic algorithm for MIS whose running time is polylogarithmic and whose processor-time product is optimal up to a polylogarithmic factor.
We introduce new techniques for deriving lower bounds on the message complexity in asynchronous distributed computation. These techniques combine the choice of specific patterns of communication delays and crossing sequence arguments with consideration of the speed of propagation of messages, together with careful counting of messages in different parts of the network. They enable us to prove the...
In practice, the average time of (deterministic or randomized) sorting algorithms seems to be more relevant than the worst case time of deterministic algorithms. Still, the many known complexity bounds for parallel comparison sorting include no nontrivial lower bounds for the average time required to sort by comparisons n elements with p processors (via deterministic or randomized algorithms). We...
This paper addresses the problem of how to adapt an algorithm designed for fixed topology networks to produce the intended results, when run in a network whose topology changes dynamically, in spite of encountering topological changes during its execution. We present a simple and unified procedure, called a reset procedure, which, when combined with the static algorithm, achieves this adaptation....
It is shown that the problem of deciding and constructing a perfect matching in bipartite graphs G with the polynomial permanents of their n × n adjacency matrices A (perm(A) = nO(1)) are in the deterministic classes NC2 and NC3, respectively. We further design an NC3 algorithm for the problem of constructing all perfect matchings (enumeration problem) in a graph G with a permanent bounded by O(nk)...
We present a randomized parallel algorithm for finding a simple cycle separator in a planar graph. The size of the separator is O(√n) and it separates the graph so that the largest part contains at most 2/8 ?? n vertices. Our algorithm takes T = O(log2(n)) time and P = O(n + f1+ε) processors, where n is the number of vertices, f is the number of faces and ε is any positive constant. The algorithm...
This paper considers mesh computers with buses, where each bus provides a broadcasting capability to the processors connected to it. We first disprove a published claim by showing that on a 2-dimensional mesh with a bus for each row, where each row must solve its own problem with data that is independent of all other rows, there are problems where the rows can cooperatively solve all subproblems faster...
The deadlock resolution problem can be informally stated as follows. There exists a set of actions, generated at different times, with some complex and contradictory precedence constraints between their executions. To resolve a deadlock, some of the actions need to be aborted; this enables to execute the remaining ones. This problem naturally arises in the context of distributed systems, e.g. communication...
Universal networks offer the advantage that they can execute programs written for simpler architectures without significant run-time overhead. In this paper we investigate simulations of tree machines; the fact that divide-and-conquer algorithms are programmed naturally on trees motivates our investigation. Among various proposals for parallel computing the boolean hypercube has emerged as a particularly...
We present a parallel randomized algorithm for finding the connected components of an undirected graph. Our algorithm takes T = O(log (n)) time and p = O(m+n/(log(n) processors, where m = number of edges and n = number of vertices. This algorithm improves the results of Cole and Vishkin1, which use O(log (n)??log (log (n))??log (log (log (n)))) time. Our algorithm is Optimal in the sense that the...
We describe a parallel algorithm for testing a graph for planarity, and for finding an embedding of a planar graph. For a graph on n vertices, the algorithm runs in O(log2 n) steps on n processors of a parallel RAM. The previous best algorithm for planarity testing in parallel polylog time ([Ja'Ja' and Simon, 82]) used a reduction to solving linear systems, and hence required Ω(n2..49...) processors...
The time complexity of sorting n elements using p ≥ n processors on Valiant's parallel comparison tree model is considered. The following results are obtained. 1. We show that this time complexity is Θ(logn/log(1+p/n)). This complements the AKS sorting network in settling the wider problem of comparison sort of n elements by p processors, where the problem for p ≤ n was resolved. To prove the lower...
We give an algorithm to construct a cell decomposition of Rd, including adjacency information, defined by any given set of rational polynomials in d variables. The algorithm runs in single exponential parallel time, and in NC for fixed d. The algorithm extends a recent algorithm of Ben-Or, Kozen, and Reif for deciding the theory of real closed fields.
We evaluate all the real and complex zeros λ1,...,λn of an n-th degree univariate polynomial with the relative precision 1/2nc for a given positive constant c. If for all g,h, log |λg/λh-1| ≥ 1/2O(n) unless λg = λh, then we need O(n3log2n) arithmetic operations or O(n2log n) steps, n log n processors. O(n2log n) operations or O(n log n) parallel steps, n processors suffice if either all the zeros...
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