Fuzzy linear programming problems : models and solutions

We investigate various types of fuzzy linear programming problems based on models and solution methods. First, we review fuzzy linear programming problems with fuzzy decision variables and fuzzy linear programming problems with fuzzy parameters (fuzzy numbers in the definition of the objective function or constraints) along with the associated duality results. Then, we review the fully fuzzy linear programming problems with all variables and parameters being allowed to be fuzzy. Most methods used for solving such problems are based on ranking functions, alpha-cuts, using duality results or penalty functions. In these methods, authors deal with crisp formulations of the fuzzy problems. Recently, some heuristic algorithms have also been proposed. In these methods, some authors solve the fuzzy problem directly, while others solve the crisp problems approximately

Improved two-phase solution strategy for multiobjective fuzzy stochastic linear programming problems with uncertain probability distribution

Multiobjective Fuzzy Stochastic Linear Programming (MFSLP) problem where the linear inequalities on the probability are fuzzy is called a Multiobjective Fuzzy Stochastic Linear Programming problem with Fuzzy Linear Partial Information on Probability Distribution (MFSLPPFI). The uncertainty presents unique difficulties in constrained optimization problems owing to the presence of conflicting goals and randomness surrounding the data. Most existing solution techniques for MFSLPPFI problems rely heavily on the expectation optimization model, the variance minimization model, the probability maximization model, pessimistic/optimistic values and compromise solution under partial uncertainty of random parameters. Although these approaches recognize the fact that the interval values for probability distribution have important significance, nevertheless they are restricted by the upper and lower limitations of probability distribution and neglected the interior values. This limitation motivated us to search for more efficient strategies for MFSLPPFI which address both the fuzziness of the probability distributions, and the fuzziness and randomness of the parameters. The proposed strategy consists two phases: fuzzy transformation and stochastic transformation. First, ranking function is used to transform the MFSLPPFI to Multiobjective Stochastic Linear Programming Problem with Fuzzy Linear Partial Information on Probability Distribution (MSLPPFI). The problem is then transformed to its corresponding Multiobjective Linear Programming (MLP) problem by using a-cut technique of uncertain probability distribution and linguistic hedges. In addition, Chance Constraint Programming (CCP), and expectation of random coefficients are applied to the constraints and the objectives respectively. Finally, the MLP problem is converted to a single-objective Linear Programming (LP) problem via an Adaptive Arithmetic Average Method (AAAM), and then solved by using simplex method. The algorithm used to obtain the solution requires fewer iterations and faster generation of results compared to existing solutions. Three realistic examples are tested which show that the approach used in this study is efficient in solving the MFSLPPFI

Duality in Fuzzy Linear Programming with Symmetric Trapezoidal Numbers

Linear programming problems with trapezoidal fuzzy numbers have recently attracted much interest. Various methods have been developed for solving these types of problems. Here, following the work of Ganesan and Veeramani and using the recent approach of Mahdavi-Amiri and Nasseri, we introduce the dual of the linear programming problem with symmetric trapezoidal fuzzy numbers and establish some duality results. The results will be useful for post optimality analysis

A Better Approach for Solving a Fuzzy Multiobjective Programming Problem by Level Sets

In this paper, we deal with the resolution of a fuzzy multiobjective programming problem using the level sets optimization. We compare it to other optimization strategies studied until now and we propose an algorithm to identify possible Pareto efficient optimal solutions

Die Optimierung von Fuzzy-Zielfunktionen in Fuzzy-(Mehrziel-)LP-Systemen - Ein kritischer Überblick

Klassische Programmierungsmodelle benötigen eindeutig bestimmte Koeffizienten und exakt festgelegte Restriktionsgrenzen. Um eine Fehlmodellierung zu vermeiden, ist daher in der Regel eine umfangreiche Informationsaufnahme und -verarbeitung notwendig. Oft wird man dennoch bei Realproblemen einige der Modellparameter nur größenordnungsmäßig angeben können. Während in den klassischen Modellen nur der Weg bleibt, diese ungenauen Größen durch "Mittelwerte" zu ersetzen, bieten Fuzzy-Modelle die Möglichkeit, die subjektiven Vorstellungen eines Entscheiders so präzise zu modellieren, wie dieser es ausdrücken will und kann. Das Risiko, mit einem falschen Bild der Realität zu arbeiten und Lösungen auszuwählen, die nicht dem Realproblem entsprechen, wird somit deutlich reduziert. Beschränken wir die Betrachtung auf den am häufigsten benutzten Modelltyp, die Linearen Programmierungsmodelle, so lässt sich eine Fuzzy-Erweiterung allgemein durch das nachfolgende Fuzzy Lineare Programmierungs-Modelle (FLP-Modell) ausdrücken. ..

A framework of distributionally robust possibilistic optimization

In this paper, an optimization problem with uncertain constraint coefficients is considered. Possibility theory is used to model the uncertainty. Namely, a joint possibility distribution in constraint coefficient realizations, called scenarios, is specified. This possibility distribution induces a necessity measure in scenario set, which in turn describes an ambiguity set of probability distributions in scenario set. The distributionally robust approach is then used to convert the imprecise constraints into deterministic equivalents. Namely, the left-hand side of an imprecise constraint is evaluated by using a risk measure with respect to the worst probability distribution that can occur. In this paper, the Conditional Value at Risk is used as the risk measure, which generalizes the strict robust and expected value approaches, commonly used in literature. A general framework for solving such a class of problems is described. Some cases which can be solved in polynomial time are identified

Fuzzy variable linear programming with fuzzy technical coefficients

Fuzzy linear programming is an application of fuzzy set theory in linear decision making problems and most of these problems are related to linear programming with fuzzy variables. In this paper an approximate but convenient method for solving these problems with fuzzy non-negative technical coefficient and without using the ranking functions, is proposed. With the help of numerical examples, the method is illustrated

A relationship between possibility-theoretical comparison indices for fuzzy sets and set relations (Study on Nonlinear Analysis and Convex Analysis)

This paper presents a new characterization of possibility-theoretical comparison indices for fuzzy sets. The indices dealt with here are a vector-ordering version of those originated by Dubois and Prade and extended by Inuiguchi, Ichihashi, and Kume. In three forms with different assumptions, it is shown that the indices can be related to six types of set relations used in the area of set optimization