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  • HU Berlin  (238)
  • Bibliothek Lübbenau - Vetschau
  • Kreisbibliothek Havelland Rathenow
  • Zentrum für Hist. Forschung Berlin
  • Berlinische Galerie
  • Römisch, Werner  (238)
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  • HU Berlin  (238)
  • Bibliothek Lübbenau - Vetschau
  • Kreisbibliothek Havelland Rathenow
  • Zentrum für Hist. Forschung Berlin
  • Berlinische Galerie
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  • 1
    Book
    Book
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_8902
    Series Statement: Stochastic Programming E-Print Series 2000,2000,26
    Content: This paper considers the two stage stochastic integer programming problems, with an emphasis on problems in which integer variables appear in the second stage. Drawing heavily on the theory of disjunctive programming, we characterize convexifications of the second stage problem and develop a decomposition-based algorithm for the solution of such problems. In particular, we verify that problems with fixed recourse are characterized by scenario-dependent second stage convexifications that have a great deal in common. We refer to this characterization as the C^3 (Common Cut Coefficients) Theorem. Based on the C^3 Theorem, we develop an algorithmic methodology that we refer to as Disjunctive Decomposition (D^2). We show that when the second stage consists of 0-1 MILP problems , we can obtain accurate second stage objective function estimates afer finitely many steps. We also set the stage for comparisions between problems in which the first stage includes only 0-1 variables and those that allow both continuous and integer variables in the first stage.
    Language: English
    URL: Volltext  (kostenfrei)
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  • 2
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_8918
    Format: 1 Online-Ressource (23 Seiten)
    Series Statement: Stochastic Programming E-Print Series 2002,2002,2
    Content: In this paper, we study alternative primal and dual formulations of multistage stochastic convex programs (SP). The alternative dual problems which can be traced to the alterna-tive primal representations, lead to stochastic analogs of standard deterministic constructs such as conjugate functions and Lagrangians. One of the by-products of this approach is that the development does not depend on dynamic programming (DP) type recursive arguments, and is therefore applicable to problems in which the objective function is non-separable (in the DP sense). Moreover, the treatment allows us to handle both continuous and discrete random variables with equal ease. We also investigate properties of the ex-pected value of perfect information (EVPI) within the context of SP, and the connection between EVPI and nonanticipativity of optimal multipliers. Our study reveals that there exist optimal multipliers that are nonanticipative if, and only if, the EVPI is zero. Finally, we provide interpretations of the retroactive nature of the dual multipliers.
    Language: English
    URL: Volltext  (kostenfrei)
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  • 3
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_8965
    Format: 1 Online-Ressource (28 Seiten)
    Series Statement: Stochastic Programming E-Print Series 2004,2004,6
    Content: This paper addresses a multi-stage stochastic integer programming formulation of the uncapacitated lot-sizing problem under uncertainty. We show that the classical $(\mathcal{l}, S)$ inequalities for the deterministic lot-sizing polytope are also valid for the stochastic lot-sizing polytope. We then extend the $(\mathcal{l}, S)$ inequalities to a general class of valid inequalities, called the $(Q, S_Q)$ inequalities, and we establish necessary and sufficient conditions which guarantee that the $(Q, S_Q)$ inequalities are facet-defining. A separation heuristic for $(Q, S_Q )$ inequalities is developed and incorporated into a branch and cut algorithm. A computational study verifies the usefulness of the $(Q, S_Q)$ inequalities as cuts.
    Language: English
    URL: Volltext  (kostenfrei)
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  • 4
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_8993
    Format: 1 Online-Ressource (26 Seiten)
    Series Statement: Stochastic Programming E-Print Series 2005,2005,12
    Content: Large scale stochastic linear programs are typically solved using a combination of mathematical programming techniques and sample-based approximations. Some methods are designed to permit sample sizes to adapt to information obtained during the solution process, while others are not. In this paper, we experimentally examine the relative merits of approximations based on adaptive samples and those based on non-adaptive samples. We begin with an examination of two versions of an adaptive technique, Stochastic Decomposition (SD), and conclude with a comparison to a nonadaptive technique, the Sample Average Approximation method (SAA). Our results indicate that there is minimal di®erence in the quality of the solutions provided by SD and SAA, although SAA requires substantially more time to execute.
    Language: English
    URL: Volltext  (kostenfrei)
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  • 5
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_9019
    Format: 1 Online-Ressource (23 Seiten)
    Series Statement: Stochastic Programming E-Print Series 2006,2006,18
    Content: This paper addresses the problem of finding cutting planes for multi-stage stochastic integer programs.We give a general method for generating cutting planes for multi-stage stochastic integer programs basedon combining inequalities that are valid for the individual scenarios. We apply the method to generatecuts for a stochastic version of a dynamic knapsack problem and to stochastic lot sizing problems. Wegive computational results which show that these new inequalities are very effective in a branch-and-cutalgorithm.
    Language: English
    URL: Volltext  (kostenfrei)
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  • 6
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_9054
    Format: 1 Online-Ressource (22 Seiten)
    Series Statement: Stochastic Programming E-Print Series 2009,2009,4
    Content: This paper introduces a new cutting plane method for two-stage stochastic mixed-integer programming (SMIP) called Fenchel decomposition (FD). FD usesa class of valid inequalities termed, FD cuts, which are derived based on Fenchel cutting planes from integer programming. We derive FD cuts based on both the first and second stage variables, and devise an FD algorithm for SMIP with binary first stage and establish finite convergence for mixed-binary second stage. We also derive alternative FD cuts based on the second stage variables only and use an idea from disjunctive programming to lift the cuts to the higher dimension space including the first stage variables. We then devise an FD-L algorithm based on the lifted FD cuts. Finally, we report on preliminary computational results based on example instances from the literature. The results are promising and show the lifted FD cuts to have better performance than the regular FD cuts. Furthermore, both the FD and FD-L algorithms outperform a standard solver on large-scaleinstances.
    Language: English
    URL: Volltext  (kostenfrei)
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  • 7
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_9051
    Format: 1 Online-Ressource (18 Seiten)
    Series Statement: Stochastic Programming E-Print Series 2009,2009,1
    Content: In this paper, a model for (joint) dynamic chance constraints is proposed and applied to an optimization problem in water reservoir management. The model relies on discretization of the decision variables but keeps the probability distribution continuous. Our approach relies on calculating probabilities of rectangles, which isparticularly useful in the presence of independent random variables but works for a moderate number of stages equally well in case of correlated variables. Numerical results are provided for two and three stages.
    Language: English
    URL: Volltext  (kostenfrei)
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  • 8
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_8875
    Format: 1 Online-Ressource (19 Seiten)
    Series Statement: Stochastic Programming E-Print Series 1999,2000,7
    Content: This paper presents an intertemporal portfolio selection model for pension funds that maximize the intertemporal expected utility of the surplus of assets net of liabilities. Following Merton (1973) it is assumed that both the asset and the liability return follow Ito processes as functions of a state variable. The optimum occurs for investors holding four funds: the market portfolio, the hedge portfolio for the state variable, the hedge portfolio for the liabilities, and the riskless asset. It is shown that pension funds should purchase hedging for liabilities. In contrast to Merton's result in the assets only case, this hedge depends exclusively on the funding ratio of a specific pension fund and not on preferences. With HARA utility the investments in the state variable hedge portfolios are also preference independent. With log utility the market portfolio investment depends only on the current funding ratio.
    Language: English
    URL: Volltext  (kostenfrei)
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  • 9
    Book
    Book
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_8870
    Series Statement: Stochastic Programming E-Print Series 1999,1999,2
    Content: In this paper we discuss Monte Carlo simulation based approximations of a stochastic programming problem. We show that if the corresponding random functions are convex piecewise smooth and the distribution is discrete, then (under mild additional assumptions) an opitmal solution of the approximating problem provides an exact optimal solution of the true problem with probability one for sufficiently large sample size. Moreover, by using theory of Large Deviations, we show that the probability of such an event approaches one exponentially fast with increase of the sample size. In particular, this happens in the case of two stage stochastic programming with recourse if the corresponding distributions are discrete. The obtained results suggest that, in such cases, Monte Carlo simulation based methods could be very efficient. We present some numerical examples to illustrate the involved ideas.
    Language: English
    URL: Volltext  (kostenfrei)
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  • 10
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, Institut für Mathematik
    UID:
    edochu_18452_9005
    Format: 1 Online-Ressource (26 Seiten)
    Series Statement: Stochastic Programming E-Print Series 2006,2006,4
    Content: In this paper we develop approximation algorithms for two-stage convex chance constrainedproblems. Nemirovski and Shapiro [16] formulated this class of problems and proposed anellipsoid-like iterative algorithm for the special case where the impact function f (x, h) is bi-affine.We show that this algorithm extends to bi-convex f (x, h) in a fairly straightforward fashion.The complexity of the solution algorithm as well as the quality of its output are functions of theradius r of the largest Euclidean ball that can be inscribed in the polytope defined by a randomset of linear inequalities generated by the algorithm [16]. Since the polytope determining ris random, computing r is diffiult. Yet, the solution algorithm requires r as an input. Inthis paper we provide some guidance for selecting r. We show that the largest value of r isdetermined by the degree of robust feasibility of the two-stage chance constrained problem –the more robust the problem, the higher one can set the parameter r. Next, we formulate ambiguous two-stage chance constrained problems. In this formulation,the random variables defining the chance constraint are known to have a fixed distribution;however, the decision maker is only able to estimate this distribution to within some error. Weconstruct an algorithm that solves the ambiguous two-stage chance constrained problem whenthe impact function f (x, h) is bi-affine and the extreme points of a certain “dual” polytope areknown explicitly.
    Language: English
    URL: Volltext  (kostenfrei)
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