Originally posted by: CPLEX12USER

Hi,

   I am having cplex object of type IloCplex and have variable array of tyoe IloNumVar[]. I am using java interface and add constraints by iterating through a huge array.

Say, I do cplex.addEq(var[i], val[i]). I add different type of constraints and have several loops through the program. When I export model, I see all the constraints added together till then and it is hard to debug where exactly problem lies if there was an issue in formulating the constraint.

Is there a way to print the constraints as interpreted by CPLEX immediately after adding these constraints using addEq, addLe etc.

Thank you!

Yes. First, if you are not already doing this, I recommend that you add names to all variables and constraints, to make them more readable. The addEq, addLe and addGe methods return a pointer to the constraints they just added. You can capture this to a variable and then just use that variable in an output statement. The .toString() method will automatically be called on the constraint.

Here is a snippet from some working code:

    IloCplex mip = new IloCplex();
    IloIntVar[] x = new IloIntVar[n];
    IloRange[] constraints = new IloRange[m];
    for (int i = 0; i < n; i++) {
      x[i] = mip.boolVar("x" + i);
    }
    for (int i = 0; i < m; i++) {
      IloLinearNumExpr sum = mip.linearNumExpr();
      for (int j = 0; j < n; j++) {
        sum.addTerm(a[i][j], x[j]);
      }
      constraints[i] = mip.addGe(sum, 1, "C" + i);
      System.out.println("Constraint " + i + ":\n" + constraints[i]);
    }

The a[][] matrix is constraint coefficients. A typical couple of lines of output is the following:

Constraint 3:
IloRange C3 : 1.0 <= (1.0*x2 + 1.0*x6 + 1.0*x7 + 1.0*x11 + 1.0*x13 + 1.0*x14 + 1.0*x15) <= infinity

Paul

Originally posted by: CPLEX12USER

It works and makes it easy to interpret the generated model.

Thank you!