Transportation Problem

Transportation Problem

The objective of this problem is to minimize the transportation cost of goods from the canneries to the warehouses, by satisfying the supply and demand constraints. In order to simplify the problem, it is assumed that there are two canneries and three warehouses. The supply data of canneries are as follows

  Supply (units)
Cannery I 350
Cannery II 650

The demands at the warehouses are as given:

  Demand (units)
Warehouse A 300
Warehouse B 300
Warehouse C 300

Shipping Cost between the canneries and warehouses are:

  Warehouse A  (cost/unit) Warehouse B (cost/unit) Warehouse C (cost/unit)
Cannery I 2.5 1.7 1.8
Cannery II 2.5 1.8 1.4

It should be noted that, this case is solved without considering the inventory. This problem has 6 design variables and 5 linear inequality constraints. The default termination criteria of linprog solver are kept unchanged for solving this problem.

Mathematical Formulation:

Minimize

.

Subject to

clc; 

nCanneries = 2;
nWarehouses = 3;
ShippingCost = [2.5 1.7 1.8; 2.5 1.8 1.4];
demand = [300 300 300]'; 
supply = [350 650]';

nVar = nCanneries*nWarehouses;
lb = zeros(1,nVar); // lower bounds of the amount of commodity to be shipped from each canneries to warehouses;

// Linear inequality constraints
// Total supply to the warehouses from a cannery should not exceed the corresponding supply limit of the same cannery
for i = 1:nCanneries
    indeX = (i-1)*nWarehouses+1:i*nWarehouses;
    As(i,indeX) = ones(1,nWarehouses);
end
Bs = supply;
As
// Total supply to a warehouses from the canneries should satisfy the corresponding demand of the same warehouses
//Ad = zeros()
for i = 1:nWarehouses
    indeX = i:nWarehouses:nVar;
    Ad(i,indeX) = -1;
end
Bd = -demand;

A = cat(1,As,Ad);
b = cat(1,Bs,Bd);

// Minimize the total transportation cost between all plants and markets
Cost = zeros(nVar,1);
for i = 1:nCanneries
    indeX = (i-1)*nWarehouses+1:i*nWarehouses;
    Cost(indeX) = (ShippingCost(i,:)');
end

[xopt,fopt,exitflag,output,lambda] = linprog(Cost,A,b,[],[],lb,[]);

// Display of results
if exitflag == 0 then
    disp(" Optimal Solution Found")
    // xopt is transformed into a nCanneries X nWarehouses sized string matrix 
    for i = 1:nCanneries
        indeX = (i-1)*nWarehouses+1:i*nWarehouses;
        X(i,1:nWarehouses) = xopt(indeX,1)';
    end
    Values = string(X);

    // Labelling each markets as M_1,M_2,...,M_nWarehouses
    Markets(1,1) = [" "];
    for j = 2:nWarehouses+1
        Markets(1,j) = strcat(["M_",string(j-1)]);
    end

    // Labelling each plants as P_1,P_2,...,P_nCanneries
    for i = 1:nCanneries
        Plants(i) = strcat(["P_",string(i)]);
    end

    table = [Markets; [Plants Values]];
    f = gcf();
    clf
    as = f.axes_size; // [width height]
    ut = uicontrol("style","table",..
    "string",table,..
    "position",[150 as(2)-220 300 87]) // => @top left corner of figure

    // Modify by hand some values in the table. Then get them back from the ui:
    matrix(ut.string,size(table))
elseif exitflag == 1 then
    mprintf('Primal Infeasible')
elseif exitflag == 2 then
    disp("Dual Infeasible")
else
    disp("Technical error encountered")
end

Expected Output

Optimal Solution.
 
  Optimal Solution Found  

      M1      M2      M3
P1    50      300     0
P2    250     0       300