However, I was pondering for the last 2 days about your response. It seems to
me that the global bound is not much use for my problem. Because the global
will give an *upper bound* for the reliability and bandwidth which is of no
use. A *lower bound* will be more useful. So I was trying to formulate the
problem to try to get a *lower bound*, but until now I am not successful of
doing it.
Another question if you do not mind.
Actually the constraint of "x1+x2<=1" is to prevent x1 and x2 to co-exists
together in the solution. If x1 and x2 are binary, then GLPK can produce a good solution.
However, if I will to use LPR, then GLPK gave a solution such that x1 and x2
*can* co-exists together in the solution, which is not what I want. Is there a
way to prevent this? That is, even if LPR is used I can prevent x1 and x2 to
co-exists together in the solution?