Displaying problem statistics

These options for displaying information in the Interactive Optimizer support large problems.

When the problem is as small as our example, it is easy to display it on the screen; however, many real problems are far too large to display. For these problems, the stats option of the display problem command is helpful. When you select stats , information about the attributes of the problem appears, but not the entire problem itself. These attributes include:

  • the number and type of constraints

  • variables

  • nonzero constraint coefficients

Try this feature by typing:


display problem stats

For our example, the following information appears: 


Problem name: example
Objective sense      :       Maximize 
Variables            :       3  [Nneg: 2,  Box: 1]
Objective nonzeros   :       3
Linear constraints   :       2  [Less: 2]
  Nonzeros           :       6
  RHS nonzeros       :       2

This information tells us that in the example there are two constraints, three variables, and six nonzero constraint coefficients. The two constraints are both of the type less-than-or-equal-to. Two of the three variables have the default nonnegativity bounds (0 ≤ x ≤ +∞) and one is restricted to a certain range (a box variable). In addition to a constraint matrix nonzero count, there is a count of nonzero coefficients in the objective function and on the righthand side. Such statistics can help to identify errors in a problem without displaying it in its entirety. The command display problem stats shows this additional information like this:


Variables            : Min LB: 0.000000         Max UB: 40.00000
Objective nonzeros   : Min   : 1.000000         Max   : 3.000000
Linear constraints   :
  Nonzeros           : Min   : 1.000000         Max   : 3.000000
  RHS nonzeros       : Min   : 20.00000         Max   : 30.00000

Another way to avoid displaying an entire problem is to display a specific part of it by using one of the following three options of the display  problem command: