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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 28 (1991), S. 185-211 
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In this paper we investigate denumerable state semi-Markov decision chains with small interest rates. We consider average and Blackwell optimality and allow for multiple closed sets and unbounded immediate rewards. Our analysis uses the existence of a Laurent series expansion for the total discounted rewards and the continuity of its terms. The assumptions are expressed in terms of a weighted supremum norm. Our method is based on an algebraic treatment of Laurent series; it constructs an appropriate linear space with a lexicographic ordering. Using two operators and a positiveness property we establish the existence of bounded solutions to optimality equations. The theory is illustrated with an example of aK-dimensional queueing system. This paper is strongly based on the work of Denardo [11] and Dekker and Hordijk [7].
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 21 (1995), S. 415-447 
    ISSN: 1572-9443
    Keywords: Zero-sum stochastic games ; discounted and expected average cost ; worst case control of queueing networks ; value iteration ; structural properties of optimal policies and value function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Zero-sum stochastic games model situations where two persons, called players, control some dynamic system, and both have opposite objectives. One player wishes typically to minimize a cost which has to be paid to the other player. Such a game may also be used to model problems with a single controller who has only partial information on the system: the dynamic of the system may depend on some parameter that is unknown to the controller, and may vary in time in an unpredictable way. A worst-case criterion may be considered, where the unknown parameter is assumed to be chosen by “nature” (called player 1), and the objective of the controller (player 2) is then to design a policy that guarantees the best performance under worst-case behaviour of nature. The purpose of this paper is to present a survey of stochastic games in queues, where both tools and applications are considered. The first part is devoted to the tools. We present some existing tools for solving finite horizon and infinite horizon discounted Markov games with unbounded cost, and develop new ones that are typically applicable in queueing problems. We then present some new tools and theory of expected average cost stochastic games with unbounded cost. In the second part of the paper we present a survey on existing results on worst-case control of queues, and illustrate the structural properties of best policies of the controller, worst-case policies of nature, and of the value function. Using the theory developed in the first part of the paper, we extend some of the above results, which were known to hold for finite horizon costs or for the discounted cost, to the expected average cost.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 36 (2000), S. 303-325 
    ISSN: 1572-9443
    Keywords: multimodular functions ; balanced sequences ; control of vacations ; polling ; service assignment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider in this paper the optimal open-loop control of vacations in queueing systems. The controller has to take actions without state information. We first consider the case of a single queue, in which the question is when should vacations be taken so as to minimize, in some general sense, workloads and waiting times. We then consider the case of several queues, in which service of one queue constitutes a vacation for others. This is the optimal polling problem. We solve both problems using new techniques from [2,4] based on multimodularity.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical methods of operations research 49 (1999), S. 1-39 
    ISSN: 1432-5217
    Keywords: Key words: Markov decision chain ; feedback control ; Blackwell optimality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract. This paper is the first part of a study of Blackwell optimal policies in Markov decision chains with a Borel state space and unbounded rewards. We prove here the existence of deterministic stationary policies which are Blackwell optimal in the class of all, in general randomized, stationary policies. We establish also a lexicographical policy improvement algorithm leading to Blackwell optimal policies and the relation between such policies and the Blackwell optimality equation. Our technique is a combination of the weighted norms approach developed in Dekker and Hordijk (1988) for countable models with unbounded rewards and of the weak-strong topology approach used in Yushkevich (1997a) for Borel models with bounded rewards.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical methods of operations research 50 (1999), S. 421-448 
    ISSN: 1432-5217
    Keywords: Key words: Markov decision chains ; Blackwell optimality ; drift and recurrence conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract. This paper is the second part of our study of Blackwell optimal policies in Markov decision chains with a Borel state space and unbounded rewards. We prove that a stationary policy is Blackwell optimal in the class of all history-dependent policies if it is Blackwell optimal in the class of stationary policies.  We also develop recurrence and drift conditions which ensure ergodicity and integrability assumptions made in the previous paper, and which are more suitable for applications. As an example we study a cash-balance model.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical methods of operations research 44 (1996), S. 387-399 
    ISSN: 1432-5217
    Keywords: Constrained Markov decision processes ; Laurent series expansion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract It is known that the value function in an unconstrained Markov decision process with finitely many states and actions is a piecewise rational function in the discount factor a, and that the value function can be expressed as a Laurent series expansion about α = 1 for α close enough to 1. We show in this paper that this property also holds for the value function of Markov decision processes with additional constraints. More precisely, we show by a constructive proof that there are numbers O = αo 〈α1 〈... 〈 αm−1 〈 αm = 1 such that for everyj = 1, 2, ...,m − 1 either the problem is not feasible for all discount factors α in the open interval (αj−1, αj) or the value function is a rational function in a in the closed interval [αj−1, αj]. As a consequence, if the constrained problem is feasible in the neighborhood of α = 1, then the value function has a Laurent series expansion about α = 1. Our proof technique for the constrained case provides also a new proof for the unconstrained case.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical methods of operations research 45 (1997), S. 281-301 
    ISSN: 1432-5217
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In this paper we will consider two-person zero-sum games and derive a general approach for solving them. We apply this approach to a queueing problem. In section 1 we will introduce the model and formulate the Key-theorem. In section 2 we develop the theory that we will use in section 3 to prove the Key-theorem. This includes a general and useful result in Lemma 2.1 on the sufficiency of stationary policies.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical methods of operations research 40 (1994), S. 91-108 
    ISSN: 1432-5217
    Keywords: Markov decision processes ; countable state space ; Linear programming ; duality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract We present an Linear Programming formulation of MDPs with countable state and action spaces and no unichain assumption. This is an extension of the Hordijk and Kallenberg (1979) formulation in finite state and action spaces. We provide sufficient conditions for both existence of optimal solutions to the primal LP program and absence of duality gap. Then, existence of a (possibly randomized) average optimal policy is also guaranteed. Existence of a stationary average optimal deterministic policy is also investigated.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical methods of operations research 47 (1998), S. 317-336 
    ISSN: 1432-5217
    Keywords: Static customer routing ; algorithm ; closed queueing network
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In this paper we analyse a closed queueing network in which customers have to be assigned to parallel queues. The routing decision may not depend on the numbers of customers in the queues. We present an algorithm and we show that it computes an average optimal policy in case of exponential service times. The algorithm also works for non-exponential service times, in which case periodic policies are found.
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  • 10
    Publication Date: 1991-12-01
    Print ISSN: 0254-5330
    Electronic ISSN: 1572-9338
    Topics: Mathematics , Economics
    Published by Springer
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