@FILE and @TEXT are used for text file input and output optimization problems in Lingo, a powerful optimization software tool. The model is set up with a set named MYSET, which is defined as the contents of the file 'myfile.txt'. The objective function is to minimize the sum of the products of the variables SHIP and COST for each element in MYSET. Constraints are also set up to ensure that the SHIP variable is greater than the NEED variable and less than the SUPPLY variable for each element in MYSET.
The data for the model is read from the file 'myfile.txt', which contains information about the variables COST, NEED, and SUPPLY. The results of the optimization are written to a text file named 'result.txt', which includes the values of the SHIP variable, the dual values of the SHIP variable, and the dual value of constraint CON1.
The contents and format of the 'myfile.txt' file include a header row with the cities Seattle, Detroit, Chicago, and Denver, followed by rows of data for the variables COST, NEED, SUPPLY, and SHIP. The model is then solved using Lingo or other optimization software to find the optimal values for the variables and constraints.
In summary, the use of @FILE and @TEXT in Lingo allows for efficient input and output of text files in optimization models. The model is set up with a specific set of data from the 'myfile.txt' file, and the results are written to a separate text file for analysis. This approach streamlines the optimization process and allows for easy manipulation of input and output data.