Computer networks in multiple criteria optimization

Abstract

Straipsnyje pristatomas metodas daugelio kriterijų optimizavimo uždaviniams spręsti naudojant kompiuterių tinklą. Čia nenaudojami lygiagretūs sprendimo procesai, bet sudėtingo optimizavimo uždavinio sprendimas tiesiog paskirstomas tinklo kompiuteriams. Pateiktuose eksperimentuose tiriama aprašytų strategijų efektyvumo priklausomybė nuo kompiuterių skaičiaus

The analysis of the method for multiple criteria optimization problems applying a computer network has been presented in the paper. The essence of the proposed method is the distribution of the concrete optimization problem into the network rather than the parallelization of some optimization method. The aim of the authors is to design and investigate the interactive strategies to solve complex multiple criteria problems by applying a computer network. The experimental trials have been carried out to investigate the comparative efficiency of the designed strategies depending on the number of computers. The optimized objective function is the weight sum of the criteria. The multiple criteria problem is iterated by selecting interacively different weight coefficients of the criteria. Therefore, the process is organized by designating the computers as the master (that coordinates the process of other computers) and the slaves (that execute different tasks). In the beginning of the process the researcher allocates a certain number of optimization problems to the network. The objective function optimization problems differ only in weight coefficients of the criteria. As soon as the task of a slave has been executed, the results is sent to the master. Every computer of the network behaves in analogous way. Whenever the researcher receives an immediate result from one of the computers, he gives a decision taking into consideration the latter and all the previous results, i. e. he selects new weight coefficients for the criteria and assigns a new task to the network. Likewise the multiple criteria problem is solved until the result is acceptable for the researcher. The application of the proposed method is illustrated on the basis of the problem for the selection of the optimal nutritive value. Message Passing Interface (MPI) software has been used. The trials have been carried out with the network of computers under the operation system Windows NT