I have a program as below:
minimize sum(i in Links) Flow[i]*Cost[i] //Cost of each link is a piecewise function
s.t.:forall(i in Nodes) ct1: sum(<i,j> in Links) Flow[<i,j>] -
sum(<j,i> in Links) Flow[<j,i>] == SupDem[i]; //SupDem=1 or -1 0r 0
for(var i in Nodes)
writeln(ct1[i].name, "--->", thisOplModel.ct1[i].dual);
the output of this script is undefined for all the duals. Any idea why ??