We propose truthful approximation mechanisms for strategic variants of the generalized assignment problem (GAP) in a payment-free environment. In GAP, a set of items has to be optimally assigned to a set of bins witho...
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We propose truthful approximation mechanisms for strategic variants of the generalized assignment problem (GAP) in a payment-free environment. In GAP, a set of items has to be optimally assigned to a set of bins without exceeding the capacity of any singular bin. In our strategic variant, bins are held by strategic agents and each agent may hide its willingness to receive some items in order to obtain items of higher values. The model has applications in auctions with budgeted bidders. (C) 2016 Elsevier B.V. All rights reserved.
We propose a simple exact algorithm for solving the generalized assignment problem. Our contribution is twofold: we reformulate the optimization problem into a sequence of decision problems, and we apply variable-fixi...
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We propose a simple exact algorithm for solving the generalized assignment problem. Our contribution is twofold: we reformulate the optimization problem into a sequence of decision problems, and we apply variable-fixing rules to solve these effectively. The decision problems are solved by a simple depth-first lagrangian branch-and-bound method, improved by our variable-fixing rules to prune the search tree. These rules rely on lagrangian reduced costs which we compute using an existing but little-known dynamic programming algorithm.
This paper studies the dynamic generalized assignment problem (DGAP) which extends the well-known generalized assignment problem by considering a discretized time horizon and by associating a starting time and a finis...
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This paper studies the dynamic generalized assignment problem (DGAP) which extends the well-known generalized assignment problem by considering a discretized time horizon and by associating a starting time and a finishing time with each task. Additional constraints related to warehouse and yard management applications are also considered. Three linear integer programming formulations of the problem are introduced. The strongest one models the problem as an origin-destination integer multi-commodity flow problem with side constraints. This model can be solved quickly for instances of small to moderate size. However, because of its computer memory requirements, it becomes impractical for larger instances. Hence, a column generation algorithm is used to compute lower bounds by solving the linear program (LP) relaxation of the problem. This column generation algorithm is also embedded in a heuristic aimed at finding feasible integer solutions. Computational experiments on large-scale instances show the effectiveness of the proposed approach. (C) 2008 Elsevier Ltd. All rights reserved.
In practice, allocating tasks to resources is often tackled in (near) real-time due to the latency of the task information and sudden task arrivals into a system. Therefore, the problem must be solved within a very sh...
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In practice, allocating tasks to resources is often tackled in (near) real-time due to the latency of the task information and sudden task arrivals into a system. Therefore, the problem must be solved within a very short time budget, when tasks are urgent or idle resources are critical to the system's performance. Local search algorithms could be a good solution to this issue. These algorithms usually focus the search on limited solution areas by applying local updates on an incumbent solution. To investigate the feasibility and performance of applying a local search algorithm to resource allocation, a special case of the generalized assignment problem (GAP) is modelled, where task profits are independent of the resources assigned and resources' capacities are identical. Then the performance of a local search algorithm to the target problems is examined empirically, characterizing the features of the GAP that make the problem hard for heuristics.
The generalized assignment problem can be viewed as the following problem of scheduling parallel machines with costs. Each job is to be processed by exactly one machine;processing job j on machine i requires time p(ij...
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The generalized assignment problem can be viewed as the following problem of scheduling parallel machines with costs. Each job is to be processed by exactly one machine;processing job j on machine i requires time p(ij) and incurs a cost of c(ij);each machine i is available for T(i) time units, and the objective is to minimize the total cost incurred. Our main result is as follows. There is a polynomial-time algorithm that, given a value C, either proves that no feasible schedule of cost C exists, or else finds a schedule of cost at most C where each machine i is used for at most 2T(i) time units. We also extend this result to a variant of the problem where, instead of a fixed processing time p(ij) there is a range of possible processing times for each machine-job pair, and the cost linearly increases as the processing time decreases. We show that these results imply a polynomial-time 2-approximation algorithm to minimize a weighted sum of the cost and the makespan, i.e., the maximum job completion time. We also consider the objective of minimizing the mean job completion time. We show that there is a polynomial-time algorithm that, given values M and T, either proves that no schedule of mean job completion time M and makespan T exists, or else finds a schedule of mean job completion time at most M and makespan at most 2T.
The well-known generalized assignment problem has many real-world applications. The assignment costs be-tween agents and tasks affected by several factors could be unstable and uncertain. In this paper, we assume that...
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The well-known generalized assignment problem has many real-world applications. The assignment costs be-tween agents and tasks affected by several factors could be unstable and uncertain. In this paper, we assume that the means and variances of assignment costs are known in advance. The idea is that the decision-maker aims to minimize the total assignment costs not only on average, but also to keep their variability as small as possible. Then, a reliability-oriented model with a nonlinear and concave objective function is formulated, and two decomposition-based methods are systematically developed for this challenging problem. The task allocation constraints are dualized and the Lagrangian relaxed problem is broken into many reliability-oriented knapsack subproblems. By the Lagrangian substitution technique, each subproblem is further decomposed into a standard knapsack problem and a simple univariate concave minimization problem. A lower bound is constructed and multipliers are optimized in dual problems by the subgradient method. Feasible solutions can be generated from the results of these reliability-oriented subproblems by Lagrangian heuristic. To further improve the convergence and solution quality, an Alternating Direction Method of Multipliers (ADMM) based decomposition approach is proposed. The augmented Lagrangian relaxed problem is split into a sequence of subproblems by the block coordinate descent method. To cope with the quadratic terms and the concave terms in these subproblems, linearization and Lagrangian substitution techniques are applied. Feasible solutions are produced from these subproblems, and solution quality can be evaluated by the lower bound provided by the Lagrangian relaxed problem. Numerical experiments are conducted on the test cases transformed from the standard benchmark instances, and the ADMM-based method has superior convergence and solution quality.
In this paper, a novel discrete differential evolution (DDE) algorithm is proposed to solve the multi-objective generalized assignment problem (mGAP), which is basically concerned with finding the optimal assignment o...
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In this paper, a novel discrete differential evolution (DDE) algorithm is proposed to solve the multi-objective generalized assignment problem (mGAP), which is basically concerned with finding the optimal assignment of jobs to agents such that each job is assigned to exactly one agent, subject to capacity constraint of agents, and aims to optimize multiple objective functions simultaneously, such as minimizing cost, minimizing time, and maximizing profit. First, the mGAP is described and a standard multi-objective mathematical programming model for nnGAP is given. Second, the DDE is presented, in which individuals are represented as the integer encoding scheme, and a novel integer-encoding-based dynamic mutation operator is employed to generate new candidate solutions. Furthermore, a sequential selection operator for dealing with multiple objectives is embedded in the proposed DDE. Finally, an extensive computational study is carried out by comparison with the enumeration algorithm and genetic algorithm, the results show that the proposed DDE is an effective algorithm for mGAR
The generalized assignment problem (GAP) has found applications in many real world problems. In this paper, we examine the GAP from a multiobjective point of view to accommodate some real world situations where more t...
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The generalized assignment problem (GAP) has found applications in many real world problems. In this paper, we examine the GAP from a multiobjective point of view to accommodate some real world situations where more than one objective is involved. An efficient LP-based heuristic is proposed to solve the biobjective generalized assignment problem (BiGAP). Extensive computational experiments are carried out to evaluate the performance of the proposed method. The results show that the proposed approach is able to generate good approximations to the nondominated frontier of the BiGAP efficiently, especially when the ratio of the number of items to the number of knapsacks is large. (C) 2006 Elsevier Ltd. All rights reserved.
This paper considers the generalized assignment problem (GAP). It is a well-known NP-hard combinatorial optimization problem that is interesting in itself and also appears as a subproblem in other problems of practica...
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This paper considers the generalized assignment problem (GAP). It is a well-known NP-hard combinatorial optimization problem that is interesting in itself and also appears as a subproblem in other problems of practical importance. A Tabu search heuristic for the GAP is proposed. The algorithm uses recent and medium-term memory to dynamically adjust the weight of the penalty incurred for violating feasibility. The most distinctive features of the proposed algorithm are its simplicity and its flexibility. These two characteristics result in an algorithm that, compared to other well-known heuristic procedures, provides good quality solutions in competitive computational times. Computational experiments have been performed in order to evaluate the behavior of the proposed algorithm. (C) 2001 Elsevier Science B.V. All rights reserved.
The generalized assignment problem is a representative NP-hard problem, for which many heuristic algorithms are known. In this article, two parallel heuristic algorithms are proposed, which are based on the ejection c...
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The generalized assignment problem is a representative NP-hard problem, for which many heuristic algorithms are known. In this article, two parallel heuristic algorithms are proposed, which are based on the ejection chain local search (EC) proposed by Yagiura et al. One is a simple parallelization called multistart parallel EC (MPEC) and the other is cooperative parallel EC (CPEC). In MPEC each search process independently explores search space while in CPEC search processes share partial information to cooperate with each other. The experimental results with 9 computers for large benchmark instances show that (1) MPEC and CPEC, respectively, run twice and 4 times faster than EC, and (2) compared to EC, the difference in quality between obtained solutions and theoretical lower bounds is reduced to 3/4 and 2/3 by MPEC and CPEC, respectively. It is said that these methods give us full benefit of parallelization, speedup and improvement for quality of solutions.
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