The exact solution of the NP-hard (nondeterministic polynomial-time hard) maximum cut problem is important in many applications across, for example, physics, chemistry, neuroscience, and circuit layout-which is also d...
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The exact solution of the NP-hard (nondeterministic polynomial-time hard) maximum cut problem is important in many applications across, for example, physics, chemistry, neuroscience, and circuit layout-which is also due to its equivalence to the unconstrained binary quadratic optimization problem. Leading solution methods are based on linear or semidefinite programming and require the separation of the so-called odd-cycle inequalities. In their groundbreaking research, F. Barahona and A. R. Mahjoub have given an informal description of a polynomial-time algorithm for this problem. As pointed out recently, however, additional effort is necessary to guarantee that the inequalities obtained correspond to facets of the cut polytope. In this paper, we shed more light on a so enhanced separation procedure and investigate experimentally how it performs in comparison with an ideal setting where one could even employ the sparsest, most violated, or geometrically most promising facet-defining odd-cycle inequalities. Summary of Contribution: This paper aims at a better capability to solve binary quadratic optimization or maximum cut problems and their various applications using integerprogramming techniques. To this end, the paper describes enhancements to a well-known algorithm for the central separation problem arising in this context;it is demonstrated experimentally that these enhancements are worthwhile from a computational point of view. The linear relaxations of the aforementioned problems are typically solved using fewer iterations and cutting planes than with a nonenhanced approach. It is also shown that the enhanced procedure is only slightly inferior to an ideal, enumerative, and, in practice, intractable global cutting-plane selection.
Continuous demands for higher performance and reliability within stringent resource budgets is driving a shift from homogeneous to heterogeneous processing platforms for the implementation of today's cyber-physica...
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Continuous demands for higher performance and reliability within stringent resource budgets is driving a shift from homogeneous to heterogeneous processing platforms for the implementation of today's cyber-physical systems (CPSs). These CPSs are typically represented as Directed-acyclic Task Graph (DTG) due to the complex interactions between their functional components that are often distributed in nature. In this article, we consider the problem of scheduling a real-time application modelled as a single DTG, where tasks may have multiple implementations designated as quality-levels, with higher quality-levels producing more accurate results and contributing to higher rewards/Quality-of-Service for the system. First, we introduce an optimal solution using integer linear programming (ILP) for a DTG with multiple quality-levels, to be executed on a heterogeneous distributed platform. However, this ILP-based optimal solution exhibits high computational complexity and does not scale for moderately large problem sizes. Hence, we propose two low-overhead heuristic algorithms called Global Slack Aware Quality-level Allocator (G-SLAQA) and Total Slack Aware Quality-level Allocator (T-SLAQA), which are able to produce satisfactorily efficient as well as fast solutions within a reasonable time. G-SLAQA, the baseline heuristic, is greedier and faster than its counter-part T-SLAQA, whose performance is at least as efficient as G-SLAQA. The efficiency of all the proposed schemes have been extensively evaluated through simulation-based experiments using benchmark and randomly generated DTGs. Through the case study of a real-world automotive traction controller, we generate schedules using our proposed schemes to demonstrate their practical applicability.
A separable two-dimensional (2-D) finite impulse response (FIR) filter can be implemented using an efficient parallel structure. The continuous coefficient separable 2-D FIR filter has already been well studied. In th...
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A separable two-dimensional (2-D) finite impulse response (FIR) filter can be implemented using an efficient parallel structure. The continuous coefficient separable 2-D FIR filter has already been well studied. In this study, the quantization of the coefficients of a separable 2-D FIR filter is addressed for the first time. Two (iterative) schemes [two-step integer linear programming algorithm (2-step-integer-LP) and two-step integer linear programming neighborhood search algorithm (2-step-integer-LP-neighbor)] for quantizing the coefficients are proposed, which have the same core idea: fixing some coefficients and optimally quantizing the other coefficients. Simulation experiment is conducted to verify the effectiveness of the proposed quantization schemes. The experimental results reveal that the two schemes both outperform the direct rounding method in terms of the design error. 2-Step-integer-LP performs slightly better than 2-step-integer-LP-neighbor. However, the former may not work, in some case, due to the large number of optimization variables. (c) 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.
This paper studies the real-time trains routing and platforming problem (RT-TRPP) in railway stations that arises from the unreliable arrival times of freight trains, flexible shunting operations and dynamic station l...
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This paper studies the real-time trains routing and platforming problem (RT-TRPP) in railway stations that arises from the unreliable arrival times of freight trains, flexible shunting operations and dynamic station layout caused by equipment failure. The feasibility of station timetable is checked before preparing a route for a train or after updating the station layout. If the station timetable is infeasible, the reassignment of trains is triggered. After introducing a problem formulation for the RT-TRPP, we propose an integerlinear Program (ILP) that strives to minimize the number of conflicting trains. In resulting timetable, directions, arrival and leaving time remain the same with networks timetable to prevent traffic disturbance of neighboring territories. If the resulting timetable is still infeasible, conflicting trains are pointed out with the cause analysis. The method is tested on real-world complex station which receives always the overload of trains' activities. The optimal full-day solution of 249 trains is obtained within 2 seconds. The efficiency of this method meets the time-critical nature of RT-TRPP.
This paper proposes a hybrid hierarchical network design scheme with wavelength conversion (H2NDS) to design a low-delay network by integrating a conventional IP network and an optical network with wavelength conversi...
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This paper proposes a hybrid hierarchical network design scheme with wavelength conversion (H2NDS) to design a low-delay network by integrating a conventional IP network and an optical network with wavelength conversion devices. In H2NDS, the network is divided into multiple domains, and wavelength converter devices and router devices are located at the relay node, an interconnection point between these domains. H2NDS is formulated as an integer linear programming problem to the sum of the delay of all end-to-end paths (delay) with constraint of the number of wavelengths in the optical network. Each end-to-end path selects the optimal relay node and selects either the router or wavelength converter devices to minimize the delay. The evaluation results showed that H2NDS significantly improved the delay performance compared to the benchmark model in which all end nodes belong to the nearest relay node, achieving a maximum reduction of 77.9 %.
Urban power systems are featured by high density of critical loads. There is an urgent need to enhance their resilience. This paper proposes an islanding control method for urban power sub-transmission system to ensur...
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This paper presents a model for coordinating lot-sizing and pricing decisions for manufacturers operating in multichannel markets with limited production capacity. Integrating these decisions is a significant challeng...
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Rolling stock maintenance is a key issue for the railway operations. Planning cyclical maintenance activities is a fundamental aspect of maintenance management, requiring a variety of operational choices. We present a...
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Rolling stock maintenance is a key issue for the railway operations. Planning cyclical maintenance activities is a fundamental aspect of maintenance management, requiring a variety of operational choices. We present a novel flow formulation approach to schedule rolling stock maintenance activities optimising both maintenance costs and train availability. The schedule takes into account cyclical maintenance activities and the decoupling between elapsed and operational time. Limited resource and depot capacity are taken into account together with operational constraints to reflect the real operations of the railway system. The proposed formulation is based on an integer linear programming (ILP) approach, which is solved using a commercial solver on randomly generated realistic instances.
The paper is motivated by real problems concerning tasks assignment to workers in medium-sized upholstered furniture plants managed using the Demand-Driven Manufacturing. Although the methodology was developed for fur...
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The paper is motivated by real problems concerning tasks assignment to workers in medium-sized upholstered furniture plants managed using the Demand-Driven Manufacturing. Although the methodology was developed for furniture plants it can be applied to other types of production plants. We involve competence coefficients, which describe the level of the worker's skills or capabilities to perform a specific task. The competence coefficients are also used to block the possibility of assigning the given task to a worker that has no skills to do it. Additionally, we involve a dummy worker to the model which guarantees the existence of a solution to the problem. We present and discuss integer linear programming Models for the posted problem that are closely related to the Generalized Assignment Problem. We also discuss the potential use of the presented methodology to solve real-life problems related to production management.
In this paper, we study a unique, rich combinatorial optimization problem that arose from helicopter aircrew training for the Royal Australian Navy. Each pilot trainee (student) has to complete a syllabus. A syllabus ...
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In this paper, we study a unique, rich combinatorial optimization problem that arose from helicopter aircrew training for the Royal Australian Navy. Each pilot trainee (student) has to complete a syllabus. A syllabus is a sequence of courses (commonly known as subjects), and each course is associated with a pass rate. A prerequisite structure exists amongst some courses. Each course has a number of repeated sessions, each spanning the same amount of time, but occupying a different set of (possibly overlapping) time slots. A feasible schedule is a sequence of course sessions such that each course in the syllabus is covered by exactly one session, and that all pre-requisite requirements are observed. The optimization problem is to simultaneously assemble course sessions to form feasible schedules, allocate students to these schedules with an objective to minimize the total time-span in completing the syllabus, while ensuring that the class size limits for each course session is not exceeded. The problem is different from the school or university time tabling family of problems due to the assembly component required. This paper is to serve as a pilot study: we derive a number of mixed-integer linear programming models and investigate their performance using test instances provided for us by our industry partner. For each of these models, we propose a number of solution strategies as topics for future research papers. From our numerical testing, it appears that the Column Generation-based approach is computationally the most promising method.
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