[Help-glpk] Finding minimum and maximum objective value

[Benjamin Poirier]

Hello,

I am currently using glpk. Thank you for the good documentation, the
"Brief example" in section 1.3.1 really helped me to start using the
library quickly. I have a question however. I would like to find both
the minimum and the maximum objective value for the same objective
function, constraints and bounds. I have tried:

[...]
glp_set_obj_dir(lp, GLP_MIN);
glp_simplex(lp, NULL);
min= glp_get_obj_val(lp);
glp_set_obj_dir(lp, GLP_MAX);
glp_simplex(lp, NULL);
max= glp_get_obj_val(lp);

but then max == min. Is there something that I have to clear/reset after
changing obj_dir before solving again?

Thank you,
-Ben