[Help-glpk] Objective value returns even though dual infeasibility is reported

[Sam Seaver]

Dear all,

I'm using Flux Variability Analysis to understand how a metabolic
network may change under different conditions.  I'm using glpk, and
for all of the reactions, I am able to get an objective value.  For
some of the reactions, glpk reports that the primal solution is
unbounded because the dual solution is infeasible.  However, the very
same program still prints out an objective value, and not necessarily
zero, or infinity.  Furthermore, the objective value is reasonable.

Firstly, I do not understand how LP can calculate an objective value
if it can prove that the primal solution is unbounded.  Secondly, I
would like to know, since the metabolic network is a published
standard, how I can tackle the dual infeasibilities without making any
changes to the network.  Is it possible to use the objective values
despite the dual infeasibilities, and whether I can or cannot, what
should I say to an audience of bioengineers about these dual
infeasibilities?

Many thanks
Sam Seaver