Re: [Help-glpk] Linear Programming Relaxation

[Michael Hennebry]

On Sun, 29 Nov 2009, RC Loh wrote:

> 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.

Getting a lower bound pretty much means finding a feasible solution.

> 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?

2-item SOS constraint perhaps?

--
Michael   address@hidden
"Pessimist: The glass is half empty.
Optimist:   The glass is half full.
Engineer:   The glass is twice as big as it needs to be."