An effective genetic algorithm approach to multiobjective resource allocation problems (MORAPs)

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Abstract

Dynamic programming (DP) is a mathematical procedure designed primarily to improve the computational efficiency of solving select mathematical programming problems by decomposing them into smaller, and hence computationally simpler, subproblems. In solving Multiple objectives Dynamic Programming Problem (MODP), classical approaches reduce the multiple objectives into a single objective of minimizing a weighted sum of objectives. The determination of these weights indicate the relative importance of the various objective. Also, if the problem scale increases, it become difficult to be dealt with even in the case of single objective because of the rapid expansion of the number of states to be considered. In this paper, we investigated the possibility of using genetic algorithms (GAs) to solve multiobjective resource allocation problems (MORAPs). This procedure eliminates the need of any user defined weight factor for each objective. Also, the proposed approach is developed to deal with the problems with both single or multiple objectives. The simulation results for multiobjective resource allocation problems (MORAP) shows that genetic algorithms (GAs) may hopefully be a new approach for such kinds of problems.

Introduction

Dynamic programming (DP) is an optimization approach that transforms a complex problem into a sequence of simpler problems; its essential characteristic is the multistage nature of the optimization procedure. More so than other optimization techniques, DP provides a general framework for analyzing many problem types. Within this framework a variety of optimization techniques can be employed to solve particular aspects of a more general formulation [10], [13]. Resource allocation problem RAP is the process of allocating resources among the various projects or business units. Resource may be a person, asset, material, or capital which can be used to accomplish a goal. A project may be a set of related tasks which have a specific goal. A goal my be objective or target, usually driven by specific future financial needs. The “best” or optimal solution may mean maximizing profits, minimizing costs, or achieving the best possible quality. An almost infinite variety of problems can be tackled this way, but here are some typical examples:

Finance and investment: Working capital management involves allocating cash to different purposes (accounts receivable, inventory, etc.) across multiple time periods, to maximize interest earnings.

Capital budgeting: involves allocating funds to projects that initially consume cash but later generate cash, to maximize a firm's return on capital.

Portfolio optimization: creating “efficient portfolios” involves allocating funds to stocks or bonds to maximize return for a given level of risk, or to minimize risk for a target rate of return.

Job shop scheduling: involves allocating time for work orders on different types of production equipment, to minimize delivery time or maximize equipment utilization. And many other application that can be formulated as resource allocation problem.

On the other hand, there has recently been a great deal of interest in promising genetic algorithm (GA) and its application to various disciplines including optimization problems [3], [4], [8]. Genetic algorithms are also being applied to a wide range of optimization and learning problems in many domains. Genetic algorithms lend themselves well to optimization problems since they are known to exhibit robustness, require no auxiliary information, and can offer significant advantages in solution methodology and optimization performance. An useful feature of genetic algorithm is to handle multiobjective function optimization [2], [4]. GAs operate on a population of candidate solutions encoded to finite bit string called chromosome. In order to obtain optimality, each chromosome exchanges information by using operators borrowed from natural genetic to produce the better solution. GAs differ from other optimization and search procedures in four ways [8]:

  • (1)

    GAs work with a coding of the parameter set, not the parameters themselves. Therefore GAs can easily handle the integer or discrete variables.

  • (2)

    GAs search from a population of points, not a single point. Therefore GAs can provide a globally optimal solutions.

  • (3)

    GAs use only objective function information, not derivatives or other auxiliary knowledge. Therefore GAs can deal with the non-smooth, non-continuous and non-differentiable functions which are actually existed in a practical optimization problem.

  • (4)

    GAs use probabilistic transition rules, not deterministic rules.


This chapter is organized as follows, the formulation of the multiobjective resource allocation Problem (RAP) are described in Section 2. Section 3 gives out representation MORAP as a network model. In Section 4, we introduce multiobjective resource allocation problem via genetic algorithm. The simulation result are discussed in Section 5. And conclusion follows in Section 6.

Section snippets

Multiobjective resource allocation problem MORAP

The general form of the multiobjective resource allocation problem is as follows [1]:
MORAP:MaxZ1(x1,x2,…,xn)=∑k=1nzk1(xk)MaxZ2(x1,x2,…,xn)=∑k=1nzk2(xk)………MaxZP(x1,x2,…,xn)=∑k=1nzkp(xk)subjecttok=1ngk(xk)⩽S,gk(xk)⩾0,xk⩾0.The reason for the label “resource allocation problem” is that finding optimal values xk (decision variables) is equivalent to allocating the “resources” s among the “activities” stages gk(xk) in such a way that objective function Z(x1,…,xn) is maximized.

The efficient solution

Representation MORAP as a network model

Resource allocation problem is to find the best way to allocate scarce resources. The resources may be raw materials, machine time or people time, money, or anything else in limited supply. The “best” or optimal solution may mean maximizing profits, minimizing costs, or achieving the best possible quality. There are many applications to resource allocation problem such as:

  • 1.

    How many inspectors to allocate to each river (or region) to monitor pollution?

  • 2.

    How many patrol cars to allocate to different

Multiobjective resource allocation problem via genetic algorithm

Multiobjective optimization problems give rise to a set of Pareto-optimal solutions, none of which can be said to be better than other in all objectives. In any interesting multiobjective optimization problem, there exists a number of such solutions which are of interest to designers and practitioners. Since no one solution is better than any other solution in the Pareto-optimal set, it is also a goal in a multiobjective optimization to find as many such Pareto-optimal solutions as possible.

Simulation results

In this section, an experimental verification of the proposed algorithm is carried out. We apply the proposed algorithm for multiobjective resource allocation problem (taken from [1]), then we compare the results MORAP obtained by dynamic programming [1], [5] and that obtained using genetic algorithms to verify the convergence of the algorithm for the optimal solution.

Consider the problem (taken from [1]) of allocating 6 workers to a certain set of 4 jobs. Table 1, Table 2 provide the expected

Conclusions

Although resource allocation problem can be approached by dynamic programming, with the increased problem scale, many stages and states must be considered, which will greatly affect the efficiency of the procedure dynamic programming in getting the optimal solution. Moreover, the DP has the difficulty when the problem scale increases, it becomes difficult to be dealt with even in the case of single objective because of the rapid expansion of the number of the states to be considered. So we

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