Optimizing unit sizes and operation within a Renewable Energy Community (REC) can match intermittent renewable energy generation with variable user energy demands. These uncertain variables are often represented by pr...
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Optimizing unit sizes and operation within a Renewable Energy Community (REC) can match intermittent renewable energy generation with variable user energy demands. These uncertain variables are often represented by pre-defined stochastic scenarios, without searching for the "best" scenarios and testing the optimization models with these scenarios. Moreover, little work both optimized RECs under uncertainty and distributed optimal life-cycle costs (investment and operation) among members. Thus, the objectives are: i) identifying the "best" set of stochastic scenarios of solar irradiance and user electricity demands and ii) assessing the accuracy of the "stochastic forecasts" of the total system costs and unit sizes, obtained by solving a stochastic programming model based on the "best" scenarios. The proposed novel procedure shifts the "present moment" back in time to split historical data into "past" and "future" periods used to identify the "best" scenarios and compare the "stochastic forecasts" with the utopic "perfect forecasts" based on the perfect knowledge of real data, respectively. The small errors between these forecasts in the optimal life-cycle costs (less than 2 %) and sizes (3-13 %) indicate good effectiveness of the suggested procedure. Also, the optimal life-cycle costs of "stochastic forecasts" are fairly distributed among users by applying the Shapley value mechanism.
stochastic first-order (SFO) methods have been a cornerstone in addressing a broad spectrum of modern machine learning (ML) challenges. However, their efficacy is increasingly questioned, especially in large-scale app...
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We introduce a general framework for continuous-time betting markets, in which a bookmaker can dy-namically control the prices of bets on outcomes of random events. In turn, the prices set by the book-maker affect the...
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We introduce a general framework for continuous-time betting markets, in which a bookmaker can dy-namically control the prices of bets on outcomes of random events. In turn, the prices set by the book-maker affect the rate or intensity of bets placed by gamblers. The bookmaker seeks an optimal price process that maximizes his expected (utility of) terminal wealth. We obtain explicit solutions or charac-terizations to the bookmaker's optimal bookmaking problem in various interesting models. (c) 2021 Elsevier B.V. All rights reserved.
We introduce and study two-stage stochastic symmetric programs with recourse to handle uncertainty in data defining (deterministic) symmetric programs in which a linear function is minimized over the intersection of a...
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We introduce and study two-stage stochastic symmetric programs with recourse to handle uncertainty in data defining (deterministic) symmetric programs in which a linear function is minimized over the intersection of an affine set and a symmetric cone. We present a Benders' decomposition-based interior point algorithm for solving these problems and prove its polynomial complexity. Our convergence analysis proved by showing that the log barrier associated with the recourse function of stochastic symmetric programs behaves a strongly self-concordant barrier and forms a self-concordant family on the first stage solutions. Since our analysis applies to all symmetric cones, this algorithm extends Zhao's results [G. Zhao, A log barrier method with Benders' decomposition for solving two-stage stochastic linear programs, Math. Program. Ser. A 90 (2001) 507-536] for two-stage stochastic linear programs, and Mehrotra and Ozevin's results [S. Mehrotra, M.G. Ozevin, Decomposition-based interior point methods for two-stage stochastic semidefinite programming, SIAM J. Optim. 18 (1) (2007) 206-222] for two-stage stochastic semidefinite programs. (C) 2013 Elsevier Inc. All rights reserved.
The network posture of omnichannel retailers, encompassing dedicated urban fulfillment centers (UFCs) and/or selected stores (omnistores) for order fulfillment, directly influences their ability to provide responsive ...
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The network posture of omnichannel retailers, encompassing dedicated urban fulfillment centers (UFCs) and/or selected stores (omnistores) for order fulfillment, directly influences their ability to provide responsive delivery services. In turn, customers' willingness to purchase online is shaped by the responsiveness level offered, impacting overall sales revenue. To address this business context, we introduce a responsive omnichannel distribution network design problem under a probabilistic, offer-dependent customer channel choice framework. At the strategic level, our approach optimizes the selection of delivery service offers by demand zone while jointly determining the number and location of UFCs and omnistores. We formulate a two-stage stochastic distribution network design model that maximizes expected profit. Demand scenarios are derived from a discrete choice model that captures customer preferences between online and offline channels, contingent on the retailer's responsiveness level. To account for last-mile delivery complexities, we employ a refined pixelization of urban delivery areas and develop a precise calculation of Order-to-Delivery Time (ODT). Managerial insights from a case study of an omnichannel retailer in France highlight the advantages of deploying UFCs and omnistores, yielding up to an 8% profit increase under high responsiveness. Our results demonstrate the effectiveness of the proposed model in capturing customer willingness to buy online, with network offerings shifting to next-day delivery in up to 60% of demand zones.
Applications of cloud computing are increasing as companies shift from on-premise IT environments to public, private, or hybrid clouds. Consequently, cloud providers use capacity planning to maintain the capacity of c...
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Applications of cloud computing are increasing as companies shift from on-premise IT environments to public, private, or hybrid clouds. Consequently, cloud providers use capacity planning to maintain the capacity of computing resources (instances) required to meet the dynamic nature of the demand (queries). However, there is a trade-off between deploying too many costly instances, and deploying too few instances and paying penalties for not being able to process queries on-time. An instance has multiple resource dimensions and executing a query consumes multiple dimensions of an instance's capacity. This detailed multi-dimensional management of cloud computing resource capacity is known as elasticity management and is an important issue faced by all cloud providers. Determining the optimal number of instances needed in a given planning horizon is challenging, due to the combinatorial nature of the optimization problem involved. We develop an optimization model and related algorithms to capture the trade-off between the resource cost versus the delayed execution penalty in software as a service applications from the cloud provider's perspective. We develop an exact approach to solve small to medium sized applications and heuristics to solve large applications. We then evaluate their performance via extensive computational analyses with real-world data and current cloud provider approaches. We also develop a stochastic framework and methodology to deal with demand uncertainty, and using two different randomly generated data sets (representing problem instances in practice), we demonstrate that robust solutions can be obtained.
We present a distributed asynchronous algorithm for solving two-stage stochastic mixed-integer programs (SMIP) using scenario decomposition, aimed at industrial-scale instances of the stochastic unit commitment (SUC) ...
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We present a distributed asynchronous algorithm for solving two-stage stochastic mixed-integer programs (SMIP) using scenario decomposition, aimed at industrial-scale instances of the stochastic unit commitment (SUC) problem. The algorithm is motivated by large differences in run times observed among scenario subproblems of SUC instances, which can result in inefficient use of distributed computing resources by synchronous parallel algorithms. Our algorithm performs dual iterations asynchronously using a block-coordinate subgradient descent method which allows performing block-coordinate updates using delayed information, while candidate primal solutions are recovered from the solutions of scenario subproblems using heuristics. We present a high performance computing implementation of the asynchronous algorithm, detailing the operations performed by each parallel process and the communication mechanisms among them. We conduct numerical experiments using SUC instances of the Western Electricity Coordinating Council system with up to 1000 scenarios and of the Central Western European system with up to 120 scenarios. We also conduct numerical experiments on generic SMIP instances from the SIPLIB library (DCAP and SSLP). The results demonstrate the general applicability of the proposed algorithm and its ability to solve industrial-scale SUC instances within operationally acceptable time frames. Moreover, we find that an equivalent synchronous parallel algorithm would leave cores idle up to 80.4% of the time on our realistic test instances, an observation which underscores the need for designing asynchronous optimization schemes in order to fully exploit distributed computing on real world applications.
We propose a novel partial sample average approximation (PSAA) framework to solve the two main types of chance-constrained linear matrix inequality (CCLMI) problems: CCLMI with random technology matrix and CCLMI with ...
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We propose a novel partial sample average approximation (PSAA) framework to solve the two main types of chance-constrained linear matrix inequality (CCLMI) problems: CCLMI with random technology matrix and CCLMI with random right-hand side. We propose a series of computationally tractable PSAA-based approximations for CCLMI problems, analyze their properties, and derive sufficient conditions that ensure convexity for the two most popular-normal and uniform-continuous distributions. We derive several semidefinite programming PSAA reformulations efficiently solved by off-the-shelf solvers and design a sequential convex approximation method for the PSAA formulations containing bilinear matrix inequalities. The proposed methods can be generalized to other continuous random variables whose cumulative distribution function can be easily computed. We carry out a comprehensive numerical study on three practical CCLMI problems: robust truss topology design, calibration, and robust control. The tests attest to the superiority of the PSAA reformulation and algorithmic framework over the scenario and sample average approximation methods. Summary of Contribution: In line with the mission and scope of IJOC, we study an important type of optimization problems, chance-constrained linear matrix inequality (CCLMI) problems, which require stochastic linear matrix inequality (LMI) constraints to be satisfied with high probability. To solve CCLMI problems, we propose a novel partial sample average approximation (PSAA) framework: (i) develop a series of computationally tractable PSAA-based approximations for CCLMI problems, (ii) analyze their properties, (iii) derive sufficient conditions ensuring convexity, and (iv) design a sequential convex approximation method. We evaluate our proposed method via a comprehensive numerical study on three practical CCLMI problems. The tests attest the superiority of the PSAA reformulation and algorithmic framework over standard benchmarks.
Industrial companies are seeking for highly flexible strategic and operational solutions to face the requirements of current dynamic markets. The aim of this work is to provide a decision support assessment for the de...
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Industrial companies are seeking for highly flexible strategic and operational solutions to face the requirements of current dynamic markets. The aim of this work is to provide a decision support assessment for the design and scheduling of a multipurpose plant under demand uncertainty, allowing the assessment of alternative risk profile solutions. A general two-stage mixed-integer linear programming (MILP) model is proposed with the goal to maximise the annualised profit of the plant operation under a set of scenarios while minimising the associated financial risk. Considering the long-term investment perspective, the Conditional Value at Risk (CVaR) measure is used to evaluate the likelihood that a specific loss or gain will exceed a certain value at risk. A bi-objective model is formulated using the augmented epsilon-constraint method to generate an approximation to the Pareto-optimal curve, illustrating the trade-offs between plant profit (with the corresponding design and scheduling decisions) and the associated financial risk. Addressing a set of propositions regarding a case-study, the conclusions highlight the advantages of the risk measure integration in support of the decision-making process, discussing the managerial insights in the assessment of diverse financial outcomes for the solution optimisation.
This paper presents a novel optimal offering framework to incorporate hydrogen system potential for frequency regulation goals. Furthermore, the presented model considers the possibility of submitting bids for a day-a...
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