Transportation and Assignment Models in Operations Research

Transportation and assignment models are special purpose algorithms of the linear programming. The simplex method of Linear Programming Problems(LPP) proves to be inefficient is certain situations like determining optimum assignment of jobs to persons, supply of materials from several supply points to several destinations and the like. More effective solution models have been evolved and these are called assignment and transportation models. The transportation model is concerned with selecting the routes between supply and demand points in order to minimize costs of transportation subject to constraints of supply at any supply point and demand at any demand point. Assume a company has 4 manufacturing plants with different capacity levels, and 5 regional distribution centres. 4 x 5 = 20 routes are possible. Given the transportation costs per load of each of 20 routes between the manufacturing (supply) plants and the regional distribution (demand) centres,Continue reading

Initial basic feasible solution of a transportation problem

Initial basic feasible solution of a transportation problem can be obtained by any of the following methods: 1. North—west corner rule The major advantage of the north—west corner rule method is that it is very simple and easy to apply. Its major disadvantage, however, is that it is not sensitive to costs and consequently yields poor initial solutions. The steps involved in determining an initial solution using north—west corner rule are as follows: Step1. Write the given transportation problem in tabular form (if not given). Step2. Go over to the north-west corner of the table. Suppose it is the (i, j)th cell. Step3. Allocate min (ai, bj) to this cell. If the min (ai , bj) = ai, then the availability of the ith origin is exhausted and demand at the jth destination remains as bj-ai and the ith row is deleted from the table. Again if min (ai, bj)Continue reading

Procedure for finding an optimum solution for transportation problem

The basic steps of the transportation method are: 1. To set up the transportation table. 2. Examine whether total supply equals total demand. If not, introduce a dummy row/column having all its cost elements as zero and Supply/Demand as the (+ive) difference of supply and demand. 3. To find an initial basic feasible solution. An initial BFS for a TP with m sources and n destinations must include m+n—1 basic variables. This initial solution may or may not be optimal. Thus, the initial solution in the transportation method serves the same purpose as the initial solution in the simplex method. There are a few methods to find the initial solution. The widely used methods for finding a initial solution are: North West corner rule Row minima method Column minima method Matrix minima method (Lowest cost entry method) Vogel’s approximation method (unit cost penalty method) (VAM) 4. To obtain an optimalContinue reading

Operations Research approach of problem solving

Operations Research approach of problem solving Optimization is the act of obtaining the best result under any given circumstance. In various practical problems we may have to take many technical or managerial decisions at several stages. The ultimate goal of all such decisions is to either maximize the desired benefit or minimize the effort required. We make decisions in our every day life without even noticing them. Decision-making is one of the main activity of a manager or executive. In simple situations decisions are taken simply by common sense, sound judgment and expertise without using any mathematics. But here the decisions we are concerned with are rather complex and heavily loaded with responsibility. Examples of such decision are finding the appropriate product mix when there are large numbers of products with different profit contributions and production requirement or planning public transportation network in a town having its own layout ofContinue reading

Introduction to Transportation Problem

Transportation problem is a particular class of linear programming, which is associated with day-to-day activities in our real life and mainly deals with logistics. It helps in solving problems on distribution and transportation of resources from one place to another. The goods are transported from a set of sources (e.g., factory) to a set of destinations (e.g., warehouse) to meet the specific requirements. In other words, transportation problems deal with the transportation of a single product manufactured at different plants (supply origins) to a number of different warehouses (demand destinations). The objective is to satisfy the demand at destinations from the supply constraints at the minimum transportation cost possible. To achieve this objective, we must know the quantity of available supplies and the quantities demanded. In addition, we must also know the location, to find the cost of transporting one unit of commodity from the place of origin to theContinue reading

Economic interpretation of linear programming duality

We see that the primal and the dual of linear programming are related mathematically, we can now show that they are also related in economic sense. Consider the economic interpretation of the duality of linear programming – first for a maximisation problem and then for a minimisation problem. The maximisation problem: Consider the following linear programming problem. The optimal solution to this problem dives production of 18 units of Xi and 8 units of x2 per week. It yields the maximum prof of a Rs. 1000, Maximise Z = 40×1 + 35×2, Subject to 2×1 + 3X2 < or = 60, Raw materials constraint per week. 4×1 + 3X2 < or = 96, Capacity constraint per week. x1,x2 > or = 0 The optimal solution to this problem gives production of 18 units of x1 and 8 units of x2 per week. It yields the maximum profit of a Rs.Continue reading