Concurrency and randomization are difcult to use correctly when program- ming. Because programs that use them no longer behave deterministically, pro- grammers must take into account the set of all possible interactio...
详细信息
Concurrency and randomization are difcult to use correctly when program- ming. Because programs that use them no longer behave deterministically, pro- grammers must take into account the set of all possible interactions and random choices that may occur. Tis dissertation describes a logic for reasoning about programs using both of these efects. Te logic extends a recent concurrent sep- aration logic with ideas from denotational semantics for probabilistic and non- deterministic choice, along with principles for probabilistic relational reasoning originally developed for sequential programs. Te resulting logic is used to verify probabilistic behaviors of a randomized concurrent counter algorithm and a two- level concurrent skip list. Te soundness of the logic, as well as the proofs of these examples, have been mechanized in Coq.
Spoken term discovery is the task of automatically identifying words and phrases in speech data by searching for long repeated acoustic patterns. Initial solutions relied on exhaustive dynamic time warping-based searc...
详细信息
This paper addresses the problem of finding the nearest neighbor (or one of the R-nearest neighbors) of a query object q in a database of n objects, when we can only use a comparison oracle. The comparison oracle, giv...
详细信息
ISBN:
(纸本)9781618395993
This paper addresses the problem of finding the nearest neighbor (or one of the R-nearest neighbors) of a query object q in a database of n objects, when we can only use a comparison oracle. The comparison oracle, given two reference objects and a query object, returns the reference object most similar to the query object. The main problem we study is how to search the database for the nearest neighbor (NN) of a query, while minimizing the questions. The difficulty of this problem depends on properties of the underlying database. We show the importance of a characterization: combinatorial disorder D which defines approximate triangle inequalities on ranks. We present a lower bound of Ω(D log n/D + D~2) average number of questions in the search phase for any randomized algorithm, which demonstrates the fundamental role of D for worst case behavior. We develop a randomized scheme for NN retrieval in O(D~3 log~2 n + D log~2 n log log n~D~3 ) questions. The learning requires asking O(nD~3 log~2 n + D log~2 n log log n~D~3) questions and O(n log~2 n/ log(2D)) bits to store.
Suppose we are given two sets R and B, each of n points in the plane. Define the cost of a matching to be the teal distance of the edges in the, matching. The minimum matching problem on Euclidean space is to find a c...
详细信息
Suppose we are given two sets R and B, each of n points in the plane. Define the cost of a matching to be the teal distance of the edges in the, matching. The minimum matching problem on Euclidean space is to find a complete bipartite matching which has the minimum cost on Euclidean space. In this paper, we are interested in the on-line minimum matching problem on Euclidean space. We assume the set R is known, but the points of set B are revealed one by one. When a point of set B arrives, we must decide what match to make involving the point. None of the matches can be changed after they are made. The on-line minimum matching problem on Euclidean space tries to minimize the cost of the complete bipartite matching that we find. This paper proposes a family of randomized algorithms, Algorithm RM(m) (1 less than or equal to m less than or equal to n), for solving this problem. When a point in the set B arrived, Algorithm RM(m) randomly chooses at most m unmatched points in the set R, and adds the minimum edge between the arriving point and the chosen points to the matching. In each decision step, the algorithm only runs in O(m) time, which is superior to the known non-randomized algorithms for this problem. In this paper, we show that Algorithm RM(m) is not a competitive on-line algorithm for 1 less than or equal to m less than or equal to n-1. However, we further show that if 2n is large, the average cost incurred by Algorithm RM(m) (1 less than or equal to m less than or equal to n) is bounded by O(root n) times the average cost of the optimal Euclidean minimum matching.
In this paper a fault diagnosis technique for electronic analog circuits is described. Diagnosis is obtained by comparing input-output measurements with examples contained in a fault dictionary, by means of a neural c...
详细信息
ISBN:
(纸本)0780366468
In this paper a fault diagnosis technique for electronic analog circuits is described. Diagnosis is obtained by comparing input-output measurements with examples contained in a fault dictionary, by means of a neural classifier. A harmonic analysis is used, i.e. the test input stimuli are sinusoidal waves. A novel method for optimizing the fault dictionary construction is proposed. In particular, the stimuli selection is optimized by means of a sensitivity analysis of the Circuit Under Test -CUT- relying on a probabilistic approach based on randomized algorithms. This technique allows removing all the hypothesis assumed by the related literature. In fact it allows to remove the small perturbation assumption and presents a poly-time solution independently from the dimension of the perturbation..
We consider the problem of scheduling VMs (Virtual Machines) in a multi-server system motivated by cloud computing applications. VMs arrive dynamically over time and require various amounts of resources (e.g., CPU, Me...
详细信息
ISBN:
(纸本)9781467399548
We consider the problem of scheduling VMs (Virtual Machines) in a multi-server system motivated by cloud computing applications. VMs arrive dynamically over time and require various amounts of resources (e.g., CPU, Memory, Storage, etc.) for the duration of their service. When a VM arrives, it is queued and later served by one of the servers that has sufficient remaining capacity to serve it. The scheduling of VMs is subject to: (i) packing constraints, i.e., multiple VMs can be be served simultaneously by a single server if their cumulative resource requirement does not violate the capacity of the server, and (ii) non-preemption, i.e., once a VM is scheduled in a server, it cannot be interrupted or migrated to another server. To achieve maximum throughput, prior results hinge on solving a hard combinatorial problem (Knapsack) at the instances that all the servers become empty (the so-called global refresh times which require synchronization among the servers). The main contribution of this paper is that it resolves these issues. Specifically, we present a class of randomized algorithms for placing VMs in the servers that can achieve maximum throughput without preemptions. The algorithms are naturally distributed, have low complexity, and each queue needs to perform limited operations. Further, our algorithms display good delay performance in simulations, comparable to delay of heuristics that may not be throughput-optimal, and much better than the delay of the prior known throughput-optimal algorithms.
In this paper efficient randomized algorithms are constructed to solve optimal robust performance controller design problems. The randomized algorithms here are based on a property from statistical learning theory kno...
详细信息
In this paper efficient randomized algorithms are constructed to solve optimal robust performance controller design problems. The randomized algorithms here are based on a property from statistical learning theory known as uniform convergence of empirical means (UCEM). It is argued that in order to assess the performance of a controller as the plant varies over a prespecified family, it is better to use the average performance of the controller as the objective function to be minimized, rather than its worst-case performance. The approach is illustrated to be efficient through an example.
randomized algorithms are a useful tool for analyzing the performance of complex uncertain systems. Their implementation requires the generation of a large number N of random samples representing the uncertainty scena...
详细信息
randomized algorithms are a useful tool for analyzing the performance of complex uncertain systems. Their implementation requires the generation of a large number N of random samples representing the uncertainty scenarios, and the corresponding evaluation of system performance. When N is very large and/or performance evaluation is costly or time consuming, it can be necessary to distribute the computational burden of such algorithms among many cooperating computing units. This paper studies distributed versions of randomized algorithms for expected value and probability estimation over a network of computing nodes with possibly time-varying communication links. Explicit a-priori bounds are provided for the sample and communication complexity of these algorithms in terms of number of local samples, number of computing nodes and communication iterations.
randomized algorithms for resource choice make use of information concerning the spread of their keyed-in data by using random samples. This can effectively improve resource utilization but can create a load imbalance...
详细信息
randomized algorithms for resource choice make use of information concerning the spread of their keyed-in data by using random samples. This can effectively improve resource utilization but can create a load imbalance naturally due to the randomness of its input space. For specific problems it is helpful to use a helper to direct the solution space in the right direction. In this paper, to enact effective resource utilization combined with optimized load balancing, a weighted randomized resource assignment algorithm is proposed. The simulation results using standard workload format datasets reveal that the proposed algorithm outperforms existing solutions in average resource utilization by 8% to 12% while improving on load balance by 5% to 11%.
The complexity of solving infinite games, including parity, mean payoff, and simple stochastic, is an important open problem in verification, automata, and complexity theory. In this paper, we develop an abstract sett...
详细信息
The complexity of solving infinite games, including parity, mean payoff, and simple stochastic, is an important open problem in verification, automata, and complexity theory. In this paper, we develop an abstract setting for studying and solving such games, based on function optimization over certain discrete structures. We introduce new classes of recursively local-global (RLG) and partial recursively local-global (PRLG) functions, and show that strategy evaluation functions for simple stochastic, mean payoff, and parity games belong to these classes. In this setting, we suggest randomized subexponential algorithms appropriate for RLG- and PRLG-function optimization. We show that the subexponential algorithms for combinatorial linear programming, due to Kalai and Matousek, Sharir, Welzl, can be adapted for optimizing the RLG- and PRLG-functions. (c) 2005 Elsevier B.V. All rights reserved.
暂无评论