Several hybrid methods have recently been proposed for solving 0-1 mixed integer programming problems. Some of these methods are based on the complete exploration of small neighborhoods. In this paper, we present seve...
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Several hybrid methods have recently been proposed for solving 0-1 mixed integer programming problems. Some of these methods are based on the complete exploration of small neighborhoods. In this paper, we present several convergent algorithms that solve a series of small sub-problems generated by exploiting information obtained from a series of relaxations. These algorithms generate a sequence of upper bounds and a sequence of lower bounds around the optimal value. First, the principle of a linear programming-based algorithm is summarized, and several enhancements of this algorithm are presented. Next, new hybrid heuristics that use linear programming and/or mixedintegerprogramming relaxations are proposed. The mixedintegerprogramming (MIP) relaxation diversifies the search process and introduces new constraints in the problem. This MIP relaxation also helps to reduce the gap between the final upper bound and lower bound. Our algorithms improved 14 best-known solutions from a set of 108 available and correlated instances of the 0-1 multidimensional Knapsack problem. Other encouraging results obtained for 0-1 MIP problems are also presented. (c) 2008 Elsevier B.V. All rights reserved.
We study the mixed 0-1 knapsack polytope, which is defined by a single knapsack constraint that contains 0-1 and bounded continuous variables, through the lifting of continuous variables fixed at their upper bounds. W...
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We study the mixed 0-1 knapsack polytope, which is defined by a single knapsack constraint that contains 0-1 and bounded continuous variables, through the lifting of continuous variables fixed at their upper bounds. We introduce the concept of a superlinear inequality and show that, in this case, lifting is significantly simpler than for general inequalities. We use the superlinearity theory, together with the traditional lifting of 0-1 variables, to describe families of facets of the mixed 0-1 knapsack polytope. Finally, we show that superlinearity results can be extended to nonsuperlinear inequalities when the coefficients of the variables fixed at their upper bounds are large.
We study the mixed 0-1 knapsack polytope, which is defined by a single knapsack constraint that contains 0-1 and bounded continuous variables. We develop a lifting theory for the continuous variables. In particular, w...
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We study the mixed 0-1 knapsack polytope, which is defined by a single knapsack constraint that contains 0-1 and bounded continuous variables. We develop a lifting theory for the continuous variables. In particular, we present a pseudo-polynomial algorithm for the sequential lifting of the continuous variables and we discuss its practical use.
In this paper we propose new hybrid heuristics for the 0-1 mixed integer programming problem, based on the variable neighbourhood decomposition search principle and on exploiting information obtained from a series of ...
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We study the mixed 0-1 knapsack polytope, which is defined by a single knapsack constraint that contains 0-1 and bounded continuous variables. We develop a lifting theory for the continuous variables. In particular, w...
详细信息
We study the mixed 0-1 knapsack polytope, which is defined by a single knapsack constraint that contains 0-1 and bounded continuous variables. We develop a lifting theory for the continuous variables. In particular, we present a pseudo-polynomial algorithm for the sequential lifting of the continuous variables and we discuss its practical use.
In this paper we propose a new method for finding an initial feasible solution for mixedinteger programs. We call it "Variable neighborhood pump", since it combines ideas of Variable neighborhood branching ...
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We study the mixed 0-1 knapsack polytope, which is defined by a single knapsack constraint that contains 0-1 and bounded continuous variables, through the lifting of continuous variables fixed at their upper bounds. W...
详细信息
We study the mixed 0-1 knapsack polytope, which is defined by a single knapsack constraint that contains 0-1 and bounded continuous variables, through the lifting of continuous variables fixed at their upper bounds. We introduce the concept of a superlinear inequality and show that, in this case, lifting is significantly simpler than for general inequalities. We use the superlinearity theory, together with the traditional lifting of 0-1 variables, to describe families of facets of the mixed 0-1 knapsack polytope. Finally, we show that superlinearity results can be extended to nonsuperlinear inequalities when the coefficients of the variables fixed at their upper bounds are large.
We investigate the optimization of transport routes of barge container ships with the objective to maximize the profit of a shipping company. This problem consists of determining the upstream and downstream calling se...
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We investigate the optimization of transport routes of barge container ships with the objective to maximize the profit of a shipping company. This problem consists of determining the upstream and downstream calling sequence and the number of loaded and empty containers transported between any two ports. We present a mixedinteger linear programming (MILP) formulation for this problem. The problem is tackled by the commercial CPLEX MIP solver and improved variants of the existing MIP heuristics: Local Branching, Variable Neighborhood Branching and Variable Neighborhood Decomposition Search. It appears that our implementation of Variable Neighborhood Branching outperforms CPLEX MIP solver both regarding the solution quality and the computational time. All other studied heuristics provide results competitive with CPLEX MIP solver within a significantly shorter amount of time. Moreover, we present a detailed case study transportation analysis which illustrates how the proposed approach can be used by managers of barge shipping companies to make appropriate decisions and solve real life problems. (C) 2013 Elsevier B. V. All rights reserved.
In this paper we propose a new hybrid heuristic for solving 0-1 mixedinteger programs based on the principle of variable neighbourhood decomposition search. It combines variable neighbourhood search with a general-pu...
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In this paper we propose a new hybrid heuristic for solving 0-1 mixedinteger programs based on the principle of variable neighbourhood decomposition search. It combines variable neighbourhood search with a general-purpose CPLEX MIP solver. We perform systematic hard variable fixing (or diving) following the variable neighbourhood search rules. The variables to be fixed are chosen according to their distance from the corresponding linear relaxation solution values. If there is an improvement, variable neighbourhood descent branching is performed as the local search in the whole solution space. Numerical experiments have proven that exploiting boundary effects in this way considerably improves solution quality. With our approach, we have managed to improve the best known published results for 8 out of 29 instances from a well-known class of very difficult MIP problems. Moreover, computational results show that our method outperforms the CPLEX MIP solver, as well as three other recent most successful MIP solution methods. (C) 2009 Elsevier Ltd. All rights reserved.
Recently several hybrid methods combining exact algorithms and heuristics have been proposed for solving hard combinatorial optimization problems. In this paper, we propose new iterative relaxation-based heuristics fo...
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Recently several hybrid methods combining exact algorithms and heuristics have been proposed for solving hard combinatorial optimization problems. In this paper, we propose new iterative relaxation-based heuristics for the 0-1 mixed integer programming problem (0-1 MIP), which generate a sequence of lower and upper bounds. The upper bounds are obtained from relaxations of the problem and refined iteratively by including pseudo-cuts in the problem. Lower bounds are obtained from the solving of restricted problems generated by exploiting information from relaxation and memory of the search process. We propose a new semi-continuous relaxation (SCR) that relaxes partially the integrality constraints to force the variables values close to 0 or 1. Several variants of the new iterative semi-continuous relaxation based heuristic can be designed by a given update procedure of multiplier of SCR. These heuristics are enhanced by using local search procedure to improve the feasible solution found and rounding procedure to restore infeasibility if possible. Finally we present computational results of the new methods to solve the multiple-choice multidimensional knapsack problem which is an NP-hard problem, even to find a feasible solution. The approach is evaluated on a set of problem instances from the literature, and compared to the results reached by both CPLEX solver and an efficient column generation-based algorithm. The results show that our algorithms converge rapidly to good lower bounds and visit new best-known solutions. (C) 2011 Elsevier Ltd. All rights reserved.
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