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Re: [Help-glpk] Linear Programming Relaxation

From: Michael Hennebry
Subject: Re: [Help-glpk] Linear Programming Relaxation
Date: Sun, 29 Nov 2009 11:53:53 -0600 (CST)
User-agent: Alpine 1.00 (DEB 882 2007-12-20)

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."

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