2018 
Boland N, Christiansen J, Dandurand B, Eberhard A, Oliveira F, 'A parallelizable augmented Lagrangian method applied to largescale nonconvexconstrained optimization problems', Mathematical Programming, 134 (2018)
© 2018 SpringerVerlag GmbH Germany, part of Springer Nature and Mathematical Optimization Society We contribute improvements to a Lagrangian dual solution approach applied to lar... [more]
© 2018 SpringerVerlag GmbH Germany, part of Springer Nature and Mathematical Optimization Society We contribute improvements to a Lagrangian dual solution approach applied to largescale optimization problems whose objective functions are convex, continuously differentiable and possibly nonlinear, while the nonrelaxed constraint set is compact but not necessarily convex. Such problems arise, for example, in the splitvariable deterministic reformulation of stochastic mixedinteger optimization problems. We adapt the augmented Lagrangian method framework to address the presence of nonconvexity in the nonrelaxed constraint set and to enable efficient parallelization. The development of our approach is most naturally compared with the development of proximal bundle methods and especially with their use of serious step conditions. However, deviations from these developments allow for an improvement in efficiency with which parallelization can be utilized. Pivotal in our modification to the augmented Lagrangian method is an integration of the simplicial decomposition method and the nonlinear block Gauss¿Seidel method. An adaptation of a serious step condition associated with proximal bundle methods allows for the approximation tolerance to be automatically adjusted. Under mild conditions optimal dual convergence is proven, and we report computational results on test instances from the stochastic optimization literature. We demonstrate improvement in parallel speedup over a baseline parallel approach.



2018 
Boland N, Christiansen J, Dandurand B, Eberhard A, Linderoth J, Luedtke J, Oliveira F, 'Combining progressive hedging with a frank¿wolfe method to compute lagrangian dual bounds in stochastic mixedinteger programming
© 2018 Society for Industrial and Applied Mathematics. We present a new primaldual algorithm for computing the value of the Lagrangian dual of a stochastic mixedinteger program ... [more]
© 2018 Society for Industrial and Applied Mathematics. We present a new primaldual algorithm for computing the value of the Lagrangian dual of a stochastic mixedinteger program (SMIP) formed by relaxing its nonanticipativity constraints. This dual is widely used in decomposition methods for the solution of SMIPs. The algorithm relies on the wellknown progressive hedging method, but unlike previous progressive hedging approaches for SMIP, our algorithm can be shown to converge to the optimal Lagrangian dual value. The key improvement in the new algorithm is an inner loop of optimized linearization steps, similar to those taken in the classical Frank¿Wolfe method. Numerical results demonstrate that our new algorithm empirically outperforms the standard implementation of progressive hedging for obtaining bounds in SMIP.



2017 
Ruther S, Boland N, Engineer FG, Evans I, 'Integrated Aircraft Routing, Crew Pairing, and Tail Assignment: BranchandPrice with Many Pricing Problems', TRANSPORTATION SCIENCE, 51 177195 (2017) [C1]



2017 
Boland N, Kalinowski T, Rigterink F, 'A polynomially solvable case of the pooling problem', Journal of Global Optimization, 67 621630 (2017) [C1]



2017 
Archetti C, Boland N, Speranza MG, 'A matheuristic for the multivehicle inventory routing problem', INFORMS Journal on Computing, 29 377387 (2017)
© 2017 INFORMS. We consider the inventory routing problem, in which a supplier has to replenish a set of customers by means of a limited fleet of capacitated vehicles over a discr... [more]
© 2017 INFORMS. We consider the inventory routing problem, in which a supplier has to replenish a set of customers by means of a limited fleet of capacitated vehicles over a discrete time horizon. The goal is to minimize the total cost of the distribution that comprises the inventory cost at the supplier and at the customers and the routing cost. We present a matheuristic that combines a tabu search and mathematical programming formulations. When compared with two exact methods on 640 small instances, the matheuristic finds 192 (48%) optima over the 402 instances with known optima and improves 125 upper bounds. Tested on 240 large instances (with up to 200 customers) for which no optimal solutions are known, it improves the best solution for 220 (92%) of the 240 instances.



2017 
Horne A, Kaur S, Szemis J, Costa A, Webb JA, Nathan R, et al., 'Using optimization to develop a ¿designer¿ environmental flow regime', Environmental Modelling and Software, 88 188199 (2017)
© 2016 Elsevier Ltd There are increasing numbers of rivers with large storages, resulting in changes to environmental condition downstream. In these systems, environmental flow re... [more]
© 2016 Elsevier Ltd There are increasing numbers of rivers with large storages, resulting in changes to environmental condition downstream. In these systems, environmental flow regimes that are specifically designed to meet environmental management objectives, whilst continuing to support economic needs, may be the best approach. A challenge remains as to how best to design these novel flow regimes. Decision support tools such as optimization provide a potential tool to achieve this. In existing tools environmental outcomes are not represented with sufficient realism and this is a major barrier to successful adoption by decisionmakers. Here, we employ conditional probability networks as a promising approach that provides both ease of modelling and a direct link to ecological outcomes and processes. We present a generic model that can be used to represent any ecological endpoint within a river system. We then demonstrate the approach using two fish species in the Yarra River, Victoria.



2017 
Boland N, Dey S, Kalinowski T, Molinaro M, Rigterink F, 'Bounding the gap between the McCormick relaxation and the convex hull for bilinear functions', Mathematical Programming, 162 523535 (2017) [C1]



2017 
Boland N, Charkhgard H, Savelsbergh M, 'The Quadrant Shrinking Method: A simple and efficient algorithm for solving triobjective integer programs', European Journal of Operational Research, 260 873885 (2017) [C1]



2017 
Boland N, Charkhgard H, Savelsbergh M, 'A new method for optimizing a linear function over the efficient set of a multiobjective integer program', EUROPEAN JOURNAL OF OPERATIONAL RESEARCH, 260 904919 (2017) [C1]



2017 
Boland N, Hewitt M, Marshall L, Savelsbergh M, 'The ContinuousTime Service Network Design Problem', OPERATIONS RESEARCH, 65 13031321 (2017)



2016 
Horne A, Szemis JM, Kaur S, Webb JA, Stewardson MJ, Costa A, Boland N, 'Optimization tools for environmental water decisions: A review of strengths, weaknesses, and opportunities to improve adoption', ENVIRONMENTAL MODELLING & SOFTWARE, 84 326338 (2016)



2016 
Boland N, Fischetti M, Monaci M, Savelsbergh M, 'Proximity Benders: a decomposition heuristic for stochastic programs', JOURNAL OF HEURISTICS, 22 181198 (2016)



2016 
Boland N, Kalinowski T, Rigterink F, 'New multicommodity flow formulations for the pooling problem', Journal of Global Optimization, 66 669710 (2016) [C1]



2016 
Boland N, Clement R, Waterer H, 'A bucket indexed formulation for nonpreemptive single machine scheduling problems', INFORMS Journal on Computing, 28 1430 (2016) [C1]
© 2016 INFORMS. Anew mixedinteger linear programming (MILP) formulation for nonpreemptive single machine scheduling problems is presented. The model is a generalisation of the cl... [more]
© 2016 INFORMS. Anew mixedinteger linear programming (MILP) formulation for nonpreemptive single machine scheduling problems is presented. The model is a generalisation of the classical time indexed (TI) model to one in which at most two jobs can be processing in each time period. Like the TI model, the new model, called the bucket indexed (BI) model, partitions the planning horizon into periods of equal length, or buckets. Unlike the TI model, the length of a period is a parameter of the BI model and can be chosen to be as long as the processing time of the shortest job. The two models are equivalent if a period is of unit length, but when longer periods are used in the BI model, it can have significantly fewer variables and nonzeros than the corresponding TI model. A computational study using weighted tardiness instances, and weighted completion time instances with release dates, reveals that the BI model significantly outperforms the TI model on instances where the minimum processing time of the jobs is large. Furthermore, the performance of the BI model is less vulnerable to increases in average processing time when the ratio of the largest processing time to the smallest is held constant.



2016 
Boland N, Charkhgard H, Savelsbergh M, 'The Lshape search method for triobjective integer programming', Mathematical Programming Computation, 8 217251 (2016) [C1]
© 2015, SpringerVerlag Berlin Heidelberg and The Mathematical Programming Society. We present a new criterion space search method, the Lshape search method, for finding all nond... [more]
© 2015, SpringerVerlag Berlin Heidelberg and The Mathematical Programming Society. We present a new criterion space search method, the Lshape search method, for finding all nondominated points of a triobjective integer program. The method is easy to implement, and is more efficient than existing methods. Moreover, it is intrinsically wellsuited for producing high quality approximate nondominated frontiers early in the search process. An extensive computational study demonstrates its efficacy.



2016 
Boland N, Kalinowski T, Kaur S, 'Scheduling arc shut downs in a network to maximize flow over time with a bounded number of jobs per time period', Journal of Combinatorial Optimization, 32 885905 (2016) [C1]



2016 
Boland N, Dumitrescu I, Froyland G, Kalinowski T, 'Minimum cardinality nonanticipativity constraint sets for multistage stochastic programming', Mathematical Programming, 157 6993 (2016) [C1]
© 2016, SpringerVerlag Berlin Heidelberg and Mathematical Optimization Society. We consider multistage stochastic programs, in which decisions can adapt over time, (i.e., at each... [more]
© 2016, SpringerVerlag Berlin Heidelberg and Mathematical Optimization Society. We consider multistage stochastic programs, in which decisions can adapt over time, (i.e., at each stage), in response to observation of one or more random variables (uncertain parameters). The case that the time at which each observation occurs is decisiondependent, known as stochastic programming with endogeneous observation of uncertainty, presents particular challenges in handling nonanticipativity. Although such stochastic programs can be tackled by using binary variables to model the time at which each endogenous uncertain parameter is observed, the consequent conditional nonanticipativity constraints form a very large class, with cardinality in the order of the square of the number of scenarios. However, depending on the properties of the set of scenarios considered, only very few of these constraints may be required for validity of the model. Here we characterize minimal sufficient sets of nonanticipativity constraints, and prove that their matroid structure enables sets of minimum cardinality to be found efficiently, under general conditions on the structure of the scenario set.



2015 
Boland NL, Eberhard AC, 'On the augmented Lagrangian dual for integer programming', Mathematical Programming, 150 491509 (2015) [C1]
© 2014, SpringerVerlag Berlin Heidelberg and Mathematical Optimization Society. We consider the augmented Lagrangian dual for integer programming, and provide a primal characteri... [more]
© 2014, SpringerVerlag Berlin Heidelberg and Mathematical Optimization Society. We consider the augmented Lagrangian dual for integer programming, and provide a primal characterization of the resulting bound. As a corollary, we obtain proof that the augmented Lagrangian is a strong dual for integer programming. We are able to show that the penalty parameter applied to the augmented Lagrangian term may be placed at a fixed, large value and still obtain strong duality for pure integer programs.



2015 
Boland N, Savelsbergh M, Waterer H, 'A decision support tool for generating shipping data for the Hunter Valley coal chain', Computers and Operations Research, 53 5467 (2015) [C1]
Strategic capacity planning is a core activity for the Hunter Valley Coal Chain Coordinator as demand for coal is expected to double in the next decade. Optimization and simulatio... [more]
Strategic capacity planning is a core activity for the Hunter Valley Coal Chain Coordinator as demand for coal is expected to double in the next decade. Optimization and simulation models are used to suggest and evaluate infrastructure expansions and operating policy changes. These models require input data in the form of shipping stems, which are arrival streams of ships at the port, together with their cargo types and composition. Creating shipping stems that accurately represent future demand scenarios has been a timeconsuming and daunting challenge. We describe an optimizationbased decision support tool that facilitates and enhances this process, and which has become an integral part of the company's work flow. The tool embeds sampling to enable the generation of multiple shipping stems for a single demand scenario, employs targets, and desirable and permissable ranges to specify and control the characteristics of the shipping stems, and uses integer programming in a hierarchical fashion to generate shipping stems that best meet the set goals. © 2014 Elsevier Ltd.



2015 
Boland N, Charkhgard H, Savelsbergh M, 'A Criterion Space Search Algorithm for Biobjective Integer Programming: The Balanced Box Method', INFORMS JOURNAL ON COMPUTING, 27 735754 (2015) [C1]



2015 
Boland N, Charkhgard H, Savelsbergh M, 'A criterion space search algorithm for biobjective mixed integer programming: The triangle splitting method', INFORMS Journal on Computing, 27 597618 (2015) [C1]
© 2015 INFORMS. We present the first criterion space search algorithm, the triangle splitting method, for finding all nondominated points of a biobjective mixed integer program. T... [more]
© 2015 INFORMS. We present the first criterion space search algorithm, the triangle splitting method, for finding all nondominated points of a biobjective mixed integer program. The algorithm is relatively easy to implement and converges quickly to the complete set of nondominated points. The algorithm maintains, at any point in time, a diverse set of nondominated points, and is thus ideally suited for fast approximation of the nondominated frontier. An extensive computational study demonstrates the efficacy of the triangle splitting method.



2015 
Boland N, Kalinowski T, Kaur S, 'Scheduling network maintenance jobs with release dates and deadlines to maximize total flow over time: Bounds and solution strategies', Computers and Operations Research, 64 113129 (2015) [C1]



2014 
Boland N, Eberhard AC, Tsoukalas A, 'A Trust Region Method for the Solution of the Surrogate Dual in Integer Programming', Journal of Optimization Theory and Applications, (2014) [C1]
We propose an algorithm for solving the surrogate dual of a mixed integer program. The algorithm uses a trust region method based on a piecewise affine model of the dual surrogate... [more]
We propose an algorithm for solving the surrogate dual of a mixed integer program. The algorithm uses a trust region method based on a piecewise affine model of the dual surrogate value function. A new and much more flexible way of updating bounds on the surrogate dual¿s value is proposed, in which numerical experiments prove to be advantageous. A proof of convergence is given and numerical tests show that the method performance is better than a state of the art subgradient solver. Incorporation of the surrogate dual value as a cut added to the integer program is shown to greatly reduce solution times of a standard commercial solver on a specific class of problems.



2014 
Boland N, Kapoor R, Kaur S, Kalinowski T, 'Scheduling Unit Time Arc Shutdowns to Maximize Network Flow Over Time: Complexity Results', NETWORKS, 63 196202 (2014) [C1]



2014 
Boland N, Kalinowski T, Waterer H, Zheng L, 'Scheduling arc maintenance jobs in a network to maximize total flow over time', DISCRETE APPLIED MATHEMATICS, 163 3452 (2014) [C1]



2014 
Boland N, Charkhgard H, Savelsbergh M, 'The triangle splitting method for biobjective mixed integer programming', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 8494 LNCS 162173 (2014)
We present the first criterion space search algorithm, the triangle splitting method, for finding the efficient frontier of a biobjective mixed integer program. The algorithm is r... [more]
We present the first criterion space search algorithm, the triangle splitting method, for finding the efficient frontier of a biobjective mixed integer program. The algorithm is relatively easy to implement and converges quickly to the complete set of nondominated points. A computational study demonstrates the efficacy of the triangle splitting method. © 2014 Springer International Publishing Switzerland.



2014 
Foster JD, Berry AM, Boland N, Waterer H, 'Comparison of mixedinteger programming and genetic algorithm methods for distributed generation planning', IEEE Transactions on Power Systems, 29 833843 (2014) [C1]



2014 
Talebian M, Boland N, Savelsbergh M, 'Pricing to accelerate demand learning in dynamic assortment planning for perishable products', European Journal of Operational Research, (2014) [C1]
Retailers, from fashion stores to grocery stores, have to decide what range of products to offer, i.e., their product assortment. Frequent introduction of new products, a recent b... [more]
Retailers, from fashion stores to grocery stores, have to decide what range of products to offer, i.e., their product assortment. Frequent introduction of new products, a recent business trend, makes predicting demand more difficult, which in turn complicates assortment planning. We propose and study a stochastic dynamic programming model for simultaneously making assortment and pricing decisions which incorporates demand learning using Bayesian updates. We show analytically that it is profitable for the retailer to use price reductions early in the sales season to accelerate demand learning. A computational study demonstrates the benefits of such a policy and provides managerial insights that may help improve a retailer's profitability. © 2014 Elsevier B.V. All rights reserved.



2014 
Boland NL, Eberhard AC, Engineer FG, Fischetti M, Savelsbergh MWP, Tsoukalas A, 'Boosting the feasibility pump', Mathematical Programming Computation, 6 255279 (2014)
© 2014, SpringerVerlag Berlin Heidelberg and Mathematical Optimization Society. The feasibility pump (FP) has proved to be an effective method for finding feasible solutions to m... [more]
© 2014, SpringerVerlag Berlin Heidelberg and Mathematical Optimization Society. The feasibility pump (FP) has proved to be an effective method for finding feasible solutions to mixed integer programming problems. FP iterates between a rounding procedure and a projection procedure, which together provide a sequence of points alternating between LP feasible but fractional solutions, and integer but LP infeasible solutions. The process attempts to minimize the distance between consecutive iterates, producing an integer feasible solution when closing the distance between them. We investigate the benefits of enhancing the rounding procedure with a clever integer line search that efficiently explores a large set of integer points. An extensive computational study on benchmark instances demonstrates the efficacy of the proposed approach.



2013 
Wallace M, Boland N, Burke E, 'Transport scheduling: Meeting the challenges of scale, complexity and uncertainty', COMPUTERS & OPERATIONS RESEARCH, 40 655656 (2013) [C3]



2013 
Akartunali K, Boland N, Evans I, Wallace M, Waterer H, 'Airline planning benchmark problemsPart I: Characterising networks and demand using limited data', COMPUTERS & OPERATIONS RESEARCH, 40 775792 (2013) [C1]



2013 
Akartunali K, Boland N, Evans I, Wallace M, Waterer H, 'Airline planning benchmark problemsPart II: Passenger groups, utility and demand allocation', COMPUTERS & OPERATIONS RESEARCH, 40 793804 (2013) [C1]



2013 
Mendes A, Boland N, Guiney P, Riveros C, 'Switch and TapChanger Reconfiguration of Distribution Networks Using Evolutionary Algorithms', IEEE TRANSACTIONS ON POWER SYSTEMS, 28 8592 (2013) [C1]



2013 
Boland N, Kalinowski T, Waterer H, Zheng L, 'Mixed integer programming based maintenance scheduling for the Hunter Valley coal chain', JOURNAL OF SCHEDULING, 16 649659 (2013) [C1]



2012 
Boland NL, Bley A, Fricke C, Froyland G, Sotirov R, 'Cliquebased facets for the precedence constrained knapsack problem', Mathematical Programming, 133 481511 (2012) [C1]



2012 
Smith OJ, Boland NL, Waterer HA, 'Solving shortest path problems with a weight constraint and replenishment arcs', Computers & Operations Research, 39 964984 (2012) [C1]



2012 
Boland NL, Eberhard AC, Engineer F, Tsoukalas A, 'A new approach to the feasibility pump in mixed integer programming', SIAM Journal on Optimization, 22 831861 (2012) [C1]



2012 
Boland NL, Gulczynski DJ, Savelsbergh MW, 'A stockyard planning problem', EURO Journal on Transportation and Logistics, 1 197236 (2012) [C1]



2011 
Baatar D, Boland NL, Brand S, Stuckey PJ, 'CP and IP approaches to cancer radiotherapy delivery optimization', Constraints, 16 173194 (2011) [C1]



2010 
Bley A, Boland NL, Fricke C, Froyland G, 'A strengthened formulation and cutting planes for the open pit mine production scheduling problem', Computers and Operations Research, 37 16411647 (2010) [C1]



2009 
Muhandiramge R, Boland NL, 'Simultaneous solution of Lagrangean dual problems interleaved with preprocessing for the Weight Constrained Shortest Path Problem', Networks, 53 358381 (2009) [C1]



2009 
Wake GMGH, Boland N, Jennings LS, 'Mixed integer programming approaches to exact minimization of total treatment time in cancer radiotherapy using multileaf collimators', Computers and Operations Research, 36 795810 (2009) [C1]



2009 
Boland N, Dumitrescu I, Froyland G, Gleixner AM, 'LPbased disaggregation approaches to solving the open pit mining production scheduling problem with block processing selectivity', Computers and Operations Research, 36 10641089 (2009) [C1]



2009 
Muhandiramge R, Boland N, Wang S, 'CONVERGENT NETWORK APPROXIMATION FOR THE CONTINUOUS EUCLIDEAN LENGTH CONSTRAINED MINIMUM COST PATH PROBLEM', SIAM JOURNAL ON OPTIMIZATION, 20 5477 (2009) [C1]



2009 
Baatar D, Boland N, Johnston R, Hamacher HW, 'A New Sequential Extraction Heuristic for Optimizing the Delivery of Cancer Radiation Treatment Using Multileaf Collimators', INFORMS JOURNAL ON COMPUTING, 21 224241 (2009) [C1]



2008 
Boland NL, Hughes BD, Merlot LTG, 'New integer linear programming approaches for course timetabling', Computers and Operations Research, 35 22092233 (2008) [C1]



2007 
Baatar D, Boland N, Brand S, Stuckey PJ, 'Minimum cardinality matrix decomposition into consecutiveones matrices: CP and IP approaches', INTEGRATION OF AI AND OR TECHNIQUES IN CONSTRAINT PROGRAMMING FOR COMBINATORIAL OPTIMIZATION PROBLEMS, PROCEEDINGS, 4510 1+ (2007) [C1]



2007 
Kallehauge B, Boland N, Madsen OBG, 'Path inequalities for the vehicle routing problem with time windows', NETWORKS, 49 273293 (2007) [C1]



2007 
Mak V, Boland N, 'Polyhedral results and exact algorithms for the asymmetric travelling salesman problem with replenishment arcs', DISCRETE APPLIED MATHEMATICS, 155 20932110 (2007) [C1]



2006 
Taylor S, Wanless IM, Boland NL, 'Distance domination and amplifier placement problems', Australasian Journal of Combinatorics, 34 117136 (2006) [C1]
We consider the optimisation problem defined on a connected undirected graph with given root vertex and a parameter s, in which we seek a spanning tree with the smallest number of... [more]
We consider the optimisation problem defined on a connected undirected graph with given root vertex and a parameter s, in which we seek a spanning tree with the smallest number of special (amplifying) vertices such that each vertex in the tree is preceded on its unique path from the root vertex by an amplifying vertex no more than s edges distant. This problem, which we call the amplified spanning tree (AST) problem, is motivated by a practical problem in local access television cable networks. We show that even restricted to planar graphs with no vertex degree exceeding four, AST is NPcomplete for every fixed s = 1. Making use of a connection with distance domination problems, we show that two related problems, including total distance domination, are also NP complete and we derive an approximability upper bound for AST.



2006 
Boland N, Dethridge J, Dumitrescu I, 'Accelerated label setting algorithms for the elementary resource constrained shortest path problem', OPERATIONS RESEARCH LETTERS, 34 5868 (2006) [C1]



2006 
Boland N, DominguezMarin P, Nickel S, Puerto J, 'Exact procedures for solving the discrete ordered median problem', COMPUTERS & OPERATIONS RESEARCH, 33 32703300 (2006) [C1]



2006 
Mak V, Boland N, 'Facets of the polytope of the Asymmetric Travelling Salesman Problem with Replenishment Arcs', DISCRETE OPTIMIZATION, 3 3349 (2006) [C1]



2004 
Boland N, Hamacher HW, Lenzen F, 'Minimizing beamon time in cancer radiation treatment using multileaf collimators', NETWORKS, 43 226240 (2004) [C1]



2004 
Boland N, Krishnamoorthy M, Ernst AT, Ebery J, 'Preprocessing and cutting for multiple allocation hub location problems', EUROPEAN JOURNAL OF OPERATIONAL RESEARCH, 155 638653 (2004) [C1]



2004 
Tran AV, Tucker RS, Boland NL, 'Amplifier placement methods for metropolitan WDM ring networks', JOURNAL OF LIGHTWAVE TECHNOLOGY, 22 25092522 (2004) [C1]



2003 
Dumitrescu I, Boland N, 'Improved preprocessing, labeling and scaling algorithms for the weightconstrained shortest path problem', NETWORKS, 42 135153 (2003) [C1]



2002 
Davey B, Boland N, Stuckey PJ, 'Efficient intelligent backtracking using linear programming', INFORMS JOURNAL ON COMPUTING, 14 373386 (2002)



2001 
Boland N, Surendonk T, 'A column generation approach to delivery planning over time with inhomogeneous service providers and service interval constraints', ANNALS OF OPERATIONS RESEARCH, 108 143156 (2001)



2001 
Dumitrescu I, Boland N, 'Algorithms for the Weight Constrained Shortest Path Problem', International Transactions in Operational Research, 8 1529 (2001)
Given a directed graph whose arcs have an associated cost, and associated weight, the weight constrained shortest path problem (WCSPP) consists of finding a leastcost path betwee... [more]
Given a directed graph whose arcs have an associated cost, and associated weight, the weight constrained shortest path problem (WCSPP) consists of finding a leastcost path between two specified nodes, such that the total weight along the path is less than a specified value. We will consider the case of the WCSPP defined on a graph without cycles. Even in this case, the problem is NPhard, unless all weights are equal or all costs are equal, however pseudopolynomial time algorithms are known. The WCSPP applies to a number of realworld problems. Traditionally, dynamic programming approaches were most commonly used, but in recent times other methods have been developed, including exact approaches based on Lagrangean relaxation, and fully polynomial approximation schemes. We will review the area and present a new exact algorithm, based on scaling and rounding of weights. International Federation of Operational Research Societies 2001.



2001 
Boland N, Krishnamoorthy M, Stuckey P, 'Untitled  Preface', ANNALS OF OPERATIONS RESEARCH, 108 1317 (2001) 


2000 
Neame P, Boland N, Ralph D, 'An outer approximate subdifferential method for piecewise affine optimization', MATHEMATICAL PROGRAMMING, 87 5786 (2000)



2000 
Ebery J, Krishnamoorthy M, Ernst A, Boland N, 'The capacitated multiple allocation hub location problem: Formulations and algorithms', EUROPEAN JOURNAL OF OPERATIONAL RESEARCH, 120 614631 (2000)



2000 
Boland NL, Clarke LW, Nemhauser GL, 'The asymmetric traveling salesman problem with replenishment arcs', EUROPEAN JOURNAL OF OPERATIONAL RESEARCH, 123 408427 (2000)



2000 
Mak V, Boland N, 'Heuristic approaches to the asymmetric travelling salesman problem with replenishment arcs', International Transactions in Operational Research, 7 431447 (2000)
The Asymmetric Travelling Salesman Problem with Replenishment Arcs (RATSP) is a new class of problem arising from work related to aircraft routing. This paper describes the proble... [more]
The Asymmetric Travelling Salesman Problem with Replenishment Arcs (RATSP) is a new class of problem arising from work related to aircraft routing. This paper describes the problem and presents heuristic approaches for solving the RATSP. We use simulated annealing to obtain feasible solutions, and hence, upper bounds on the optimum value, and solve a Lagrangean dual problem using a subgradient optimization method to obtain lower bounds. While previous methods failed to obtain optimal solutions to some problem classes after 2 h of computation time, with average gaps ranging from 15% to 30%, our heuristic approaches take only 1520 min to obtain feasible solutions, with gaps of less than 3%. We give computational results comparing these approaches. © 2000 Blackwell Publishing Ltd.



1998 
Barnhart C, Boland NL, Clarke LW, Johnson EL, Nemhauser GL, Shenoi RG, 'Flight string models for aircraft fleeting and routing', TRANSPORTATION SCIENCE, 32 208220 (1998)



1997 
Boland NL, 'A dualactiveset algorithm for positive semidefinite quadratic programming', MATHEMATICAL PROGRAMMING, 78 127 (1997)



1995 
BOLAND NL, ERNST AT, GOH CJ, MEES AI, 'OPTIMAL 2COMMODITY FLOWS WITH NONLINEAR COSTFUNCTIONS', JOURNAL OF THE OPERATIONAL RESEARCH SOCIETY, 46 11921207 (1995)



1994 
Boland NL, Ernst AT, Goh CJ, Mees AI, 'A faster version of the ASG algorithm', Applied Mathematics Letters, 7 2327 (1994)



1992 
BOLAND N, GOH CJ, MEES AI, 'AN ALGORITHM FOR NONLINEAR NETWORK PROGRAMMING  IMPLEMENTATION, RESULTS AND COMPARISONS', JOURNAL OF THE OPERATIONAL RESEARCH SOCIETY, 43 979992 (1992)



1991 
BOLAND N, GOH CJ, MEES AI, 'AN ALGORITHM FOR SOLVING QUADRATIC NETWORK FLOW PROBLEMS', APPLIED MATHEMATICS LETTERS, 4 6164 (1991)



1990 
BOLAND N, MEES AI, 'NEW METHODS FOR MULTICOMMODITY FLOWS', COMPUTERS & MATHEMATICS WITH APPLICATIONS, 20 2938 (1990)


