We present a novel methodology for the automated resource analysis of non-deterministic, probabilistic imperative programs, which gives rise to a modular approach. Program fragments are analysed in full independence. ...
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We present a novel methodology for the automated resource analysis of non-deterministic, probabilistic imperative programs, which gives rise to a modular approach. Program fragments are analysed in full independence. Moreover, the established results allow us to incorporate sampling from dynamic distributions, making our analysis applicable to a wider class of examples, for example the Coupon Collector's problem. We have implemented our contributions in the tool eco-imp, exploiting a constraint-solver over iterative refineable cost functions facilitated by off-the-shelf SMT solvers. We provide ample experimental evidence of the prototype's algorithmic power. Our experiments show that our tool runs typically at least one order of magnitude faster than comparable tools. On more involved examples, it may even be the case that execution times of seconds become milliseconds. At the same time we retain the precision of existing tools. The extensions in applicability and the greater efficiency of our prototype, yield scalability of sorts. This effects into a wider class of examples, whose expected cost analysis can be thus be performed fully automatically.
LetX1,...,X n be independent identically distributedRd-valued random vectors, and letA n =A(X1,...,X n ) be a subset of {X1,...,X n }, invariant under permutations of the data, and possessing the inclusion property (X...
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LetX1,...,X n be independent identically distributedRd-valued random vectors, and letA n =A(X1,...,X n ) be a subset of {X1,...,X n }, invariant under permutations of the data, and possessing the inclusion property (X1∈A n impliesX1∈A i for alli≤n). For example, the convex hull, the collection of all maximal vectors, the set of isolated points and other structures satisfy these *** n be the cardinality ofA n . We show that for allp≥1, there exists a universal constantC p >0 such thatE(N p n )≤C p max (1,Ep) where. This complements Jensen's lower bound for thep-th moment:E(N p n )≥Ep(N n ).The inequality is applied to the expected time analysis of algorithms in computational geometry. We also give necessary and sufficient conditions onE(N n ) for linear expected time behaviour of divide-and-conquer methods for findingA n .
In this paper we propose a random CSP model, called Model GB, which is a natural generalization of standard Model B. This paper considers Model GB in the case where each constraint is easy to satisfy. In this case Mod...
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In this paper we propose a random CSP model, called Model GB, which is a natural generalization of standard Model B. This paper considers Model GB in the case where each constraint is easy to satisfy. In this case Model GB exhibits non-trivial behaviour (not trivially satisfiable or unsatisfiable) as the number of variables approaches infinity. A detailed analysis to obtain an asymptotic estimate (good to 1+o(1)) of the average number of nodes in a search tree used by the backtracking algorithm on Model GB is also presented. It is shown that the average number of nodes required for finding all solutions or proving that no solution exists grows exponentially with the number of variables. So this model might be an interesting distribution for studying the nature of hard instances and evaluating the performance of CSP algorithms. In addition, we further investigate the behaviour of the average number of nodes as r (the ratio of constraints to variables) varies. The results indicate that as r increases, random CSP instances get easier and easier to solve, and the base for the average number of nodes that is exponential in n tends to 1 as r approaches infinity. Therefore, although the average number of nodes used by the backtracking algorithm on random CSP is exponential, many CSP instances will be very easy to solve when r is sufficiently large.
In acoustic echo cancellation (AEC) systems, the partitioned block frequency-domain adaptive filter (PBFDAF) algorithm is commonly adopted to improve the computational efficiency and convergence rate. However, the PBF...
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In acoustic echo cancellation (AEC) systems, the partitioned block frequency-domain adaptive filter (PBFDAF) algorithm is commonly adopted to improve the computational efficiency and convergence rate. However, the PBFDAF algorithm introduces an inherent delay. Delayless PBFDAF algorithms have been proposed to tackle this issue. However, the complexity of the existing delayless PBFDAF algorithms is high. Some have high average complexity, but others have high peak complexity. A computationally efficient delayless PBFDAF algorithm is proposed in this letter to reduce both the average and peak complexity. Moreover, a delay compensation method is presented to compensate the error path delay and thus speed up the convergence rate. Simulation results demonstrate that the convergence and tracking performance of the new algorithm with delay compensation is comparable with that of the PBFDAF algorithm.
Computing max{a1+ b1, a2+ b2, ... ,an+ bn} trivially takes n additions. We show that if we are given the ranking for the a"s and the b"s separately, then an algorithm exists which will compute the maximum in...
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Computing max{a1+ b1, a2+ b2, ... ,an+ bn} trivially takes n additions. We show that if we are given the ranking for the a"s and the b"s separately, then an algorithm exists which will compute the maximum in ≅2n additions on the average. This can be generalized to yield an efficient algorithm to compute max{h(a1,b1), h(a2,b2),..., h(an, bn)} where h(x,y) is monotone increasing in x and y. Another generalization shows an efficient way of computing the maximum norm of a difference between two vectors. Applications are shown in pattern classification and computational geometry.
The following NP-complete problem is considered: Given a graph G and a positive integer K, can the vertices of G be properly colored in K (or fewer) colors? It is shown that the backtrack search tree for this problem ...
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The following NP-complete problem is considered: Given a graph G and a positive integer K, can the vertices of G be properly colored in K (or fewer) colors? It is shown that the backtrack search tree for this problem has an average of O(1) nodes, as V is equal to the absolute value of V(G) grows without bound. The NP-complete problem can thus be solved by an algorithm that certainly yields the correct answer. For example, a backtrack search tree for 3-coloring a graph has an average of approximately 197 nodes, averaged over all graphs of all sizes. This means that, typically, the algorithm will never even look at most of the input data and will stop with ''no.'' Although it is clear that this must happen often, it is noteworthy that it happens often enough that the few cases of exponentially long search time do not disturb the conclusion that the average search tree is of bounded size.
Uniform random generators deliver a simple empirical means to estimate the average complexity of an algorithm. We present a general rejection algorithm that generates sequential letter-to-letter transducers up to isom...
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Uniform random generators deliver a simple empirical means to estimate the average complexity of an algorithm. We present a general rejection algorithm that generates sequential letter-to-letter transducers up to isomorphism. We also propose an original parametric random generation algorithm to produce sequential letter-to-letter transducers with a fixed number of transitions. We tailor this general scheme to randomly generate deterministic tree walking automata and deterministic top-down tree automata. We apply our implementation of the generator to the estimation of the average complexity of a deterministic tree walking automata to nondeterministic top-down tree automata construction we also implemented. (C) 2010 Elsevier B.V. All rights reserved.
Continuous random search methods with an average complexity given by O(log(1/ε)) for ε → 0 where ε is a given accuracy were presented in a recent paper. In this article an example of an O(log log(1/ε)) method is ...
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Continuous random search methods with an average complexity given by O(log(1/ε)) for ε → 0 where ε is a given accuracy were presented in a recent paper. In this article an example of an O(log log(1/ε)) method is presented and illustrated.
We give an upper bound for the average complexity (i.e. the expected number of steps until termination) for a continuous random search algorithm using results from renewal theory. It is thus possible to show that for ...
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We give an upper bound for the average complexity (i.e. the expected number of steps until termination) for a continuous random search algorithm using results from renewal theory. It is thus possible to show that for a predefined accuracy ε, the average complexity of the algorithm is O(–log ε) for ε → 0 which is optimal up to a constant factor.
An algorithm for the SATISFIABILITY problem is presented and a probabilistic analysis is performed. The analysis is based on an instance distribution which is parametrized to simulate a variety of sample characteristi...
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