This paper aims at solving a nonconvex mixed integer nonlinear programming (MINLP) model used to solve a refinery crude-oil operations scheduling problem. The, model is mostly linear but contains bilinear products of ...
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ISBN:
(纸本)9783642019289
This paper aims at solving a nonconvex mixed integer nonlinear programming (MINLP) model used to solve a refinery crude-oil operations scheduling problem. The, model is mostly linear but contains bilinear products of continuous variables in the objective function. It is possible to define a linear relaxation of the model leading to a weak bound on the objective value of the optimal solution. A typical method to circumvent this issue;is to discretize the continuous space and to use linear relaxation constraints based on variables lower and upper bounds (e.g. McCormick convex envelopes) on each subdivision of the continuous space. This work explores another approach involving constraint programming (CP). The idea is to use all additional CP model which is used to tighten the bounds of the continuous variables involved in bilinear terms and then generate cuts based on McCormick convex envelopes. These cuts are then added to the mixed integer linear program (MILP) during the search leading to a tighter linear relaxation of the MINLP. Results show large reductions of the optimality gap of a two step MILP-NLP solution method due to the tighter linear relaxation obtained.
Correlated or discriminative pattern mining is concerned with finding the highest scoring patterns w.r.t. a correlation measure (such as information gain). By reinterpreting correlation measures in ROC space and formu...
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ISBN:
(纸本)9781605584959
Correlated or discriminative pattern mining is concerned with finding the highest scoring patterns w.r.t. a correlation measure (such as information gain). By reinterpreting correlation measures in ROC space and formulating correlated itemset mining as a constraint programming problem, we obtain new theoretical insights with practical benefits. More specifically, we contribute 1) an improved bound for correlated itemset miners, 2) a novel iterative pruning algorithm to exploit the bound, and 3) an adaptation of this algorithm to mine all itemsets on the convex hull in ROC space. The algorithm does not depend on a minimal frequency threshold and is shown to outperform several alternative approaches by orders of magnitude, both in runtime and in memory requirements.
constraint programming is a powerful paradigm for solving Combinatorial Problems. In this solver approach, Enumeration Strategies are crucial for resolution performances. In a previous work, we proposed a framework to...
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ISBN:
(纸本)9780769539331
constraint programming is a powerful paradigm for solving Combinatorial Problems. In this solver approach, Enumeration Strategies are crucial for resolution performances. In a previous work, we proposed a framework to reactively change strategies showing bad performances, and to use metabacktracks to restore better states when bad decisions were made. In this paper, we design and evaluate strategies to improve resolution performances of a set of problems. Experimental results show the effectiveness of our approach.
In this paper we present a constraint satisfaction model for the steelmaking-continuous casting scheduling problem solved by constraint programming methods. The problem is described with parallel machines in each proc...
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ISBN:
(纸本)9780769536880
In this paper we present a constraint satisfaction model for the steelmaking-continuous casting scheduling problem solved by constraint programming methods. The problem is described with parallel machines in each processing stage, and the capacity of each machine is limited, and then there are different constraints in the problem, such as process routing constraint, temporal constraint and so on. The model of the problem is demonstrated with real data from practical production data. Based on the constraint programming toolkits, the model is easily established and solved quickly. Use heuristic algorithm to get the optimization solution after finding a feasible solution. The computational results of the problem displayed with a timetable for planned charges in the end of the paper show that the method for this model is feasible.
Due to the complexity of nurse rostering problems (NRPs), constraint programming (CP) approaches on their own have shown to be ineffective in solving these highly constrained problems. We investigate a two-stage hybri...
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ISBN:
(纸本)9781848822146
Due to the complexity of nurse rostering problems (NRPs), constraint programming (CP) approaches on their own have shown to be ineffective in solving these highly constrained problems. We investigate a two-stage hybrid CP approach on real world benchmark NRPs. In the first stage, a constraint satisfaction model is used to generate weekly rosters consist of high quality shift sequences satisfying a subset of constraints. An iterative forward search is then adapted to extend them to build complete feasible solutions. Variable and value selection heuristics are employed to improve the efficiency. In the second stage, a simple Variable Neighborhood Search is used to quickly improve the solution obtained. The basic idea of the hybrid approach is based on the observations that high quality nurse rosters consist of high quality shift sequences. By decomposing the problems into solvable sub-problems for CP, the search space of the original problems are significantly reduced. The results on benchmark problems demonstrate the efficiency of this hybrid CP approach when compared to the state-of-the-art approaches in the literature.
Routing vehicles to serve customers is a problem that naturally arises in many distribution systems. Moreover, fleet management requires fast algorithms able to cope with continuously changing needs. Many efforts have...
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ISBN:
(纸本)9788469254141
Routing vehicles to serve customers is a problem that naturally arises in many distribution systems. Moreover, fleet management requires fast algorithms able to cope with continuously changing needs. Many efforts have been addressed to tackle different vehicle routing problem's variants. Among them, the pick up and delivery problem with time windows (PDTW) has received far less attention despite its relevance from practical and theoretical perspectives. The present paper provides a hybrid approach to the PDTW based on constraint programming paradigm and local search. Indeed, the proposed algorithm includes some performance improvements to enhance its efficiency. Thus, this hybrid approach may provide a solution to problems otherwise intractable in a reasonable computational time, as shown in the presented results. Due to these characteristics, the proposed algorithm may be an efficient tool in decision making support, as well as a mechanism able to provide an initial solution for subsequent optimization techniques.
VLSI chips design is becoming increasingly complex and calling for more and more automation. Many chip design problems can be formulated is constraint problems and are potentially amenable to CP techniques. To the bes...
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ISBN:
(数字)9783642042447
ISBN:
(纸本)9783642042430
VLSI chips design is becoming increasingly complex and calling for more and more automation. Many chip design problems can be formulated is constraint problems and are potentially amenable to CP techniques. To the best of our knowledge, though there has been little CP work in this domain to date. We describe a successful application of a CP based tool to a particular pin-assignment problem hi which tens of thousands of phis (i.e.;connection points) belonging to internal units on the chip must be placed within their units so as to satisfy certain constraints and optimize the wirability of the design. Our tool has been tested on read IBM designs and is now being integrated into IBM's chip development environment.
This paper presents a first approach to a constraint programming-based library for the modelling of general vehicle routing problems (VRP). In this work we present a set of constraints and cost functions written in EC...
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This paper presents a first approach to a constraint programming-based library for the modelling of general vehicle routing problems (VRP). In this work we present a set of constraints and cost functions written in ECLiPSe, a well known constraint programming (CP) language, which can be combined to build different VRP models without rewriting.
The paper introduces the concept of a crystalline-like model of a computer communication network (CCN) composed of routers forming a repeating or periodic arrangement. The considered homogenous network assumes the sam...
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The paper introduces the concept of a crystalline-like model of a computer communication network (CCN) composed of routers forming a repeating or periodic arrangement. The considered homogenous network assumes the same routers servicing the same number of transmissions form an array. In such a network several isomorphic sub-networks encompassing packet transmission processes serviced by each router, interact each other as to provide a variety of demand-responsive host-server transmission services. In that context, a crystalline-like layout of physically different, however functionally identical, routers provides a homogenous array supporting computer network flows. In turn, packet transmission flows are treated as multimodal processes encompassing arbitrarily given inter-computer communications. Assuming the packets passing their origin-destination routes are synchronized by the same mechanism of packet transmission the problem boils down to a communication processes scheduling. Since concurrent transmission flows are processed along the same presumed routes, hence the schedules sought are cyclic ones. In general case, cycles of multimodal processes depend on CNN's periodicity. That objective to develop conditions allowing one to calculate the cyclic schedule of whole CCN while taking into account only periodicity of its repeating isomorphic structure.
Picat is a new and interesting programming language,combing many different programming paradigms:logic programming,imperative programming,functional programming,constraint programming,and *** paper is a personal discu...
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Picat is a new and interesting programming language,combing many different programming paradigms:logic programming,imperative programming,functional programming,constraint programming,and *** paper is a personal discussion of some of Picat's features with several code examples.
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