Adding constraints and bounds

To add constraints or bounds to a problem in the Interactive Optimizer, use these commands and options.

If you wish to add either new constraints or bounds to your problem, use the add command. This command is similar to the enter command in the way it is used, but it has one important difference: the enter command is used to start a brand new problem, whereas the add command only adds new information to the current problem.

Suppose that in the example you need to add a third constraint:

x1 + 2x2 + 3x3 ≥ 50

You may do either interactively or from a file.

Adding interactively

Type the add command, then enter the new constraint on the blank line. After validating the constraint, the cursor moves to the next line. You are in an environment identical to that of the enter command after having issued subject to . At this point you may continue to add constraints or you may type bounds and enter new bounds for the problem. For the present example, type end to exit the add command. Your session should look like this:


add 
Enter new constraints and bounds [‘end’ terminates]:
x1 + 2x2 + 3x3 >= 50 
end 
Problem addition successful.

When the problem is displayed again, the new constraint appears, like this:


display problem all 

Maximize
 obj: x1 + 2 x2 + 3 x3
Subject To
 c1: - x1 +   x2 +   x3 <= 20
 c2: x1 - 3 x2 +   x3 <= 30
 c3: x1 + 2 x2 + 3 x3 >= 50
Bounds
 0 <= x1 <= 40
 All other variables are >= 0.
end

Adding from a file

Alternatively, you may read in new constraints and bounds from a file. If you enter a file name after the add command, CPLEX will read a file matching that name. The file contents must comply with standard CPLEX LP format. CPLEX does not prompt for a file name if none is entered. Without a file name, interactive entry is assumed.

Summary

The general syntax for the add command is:

add

add filename