> I have the following small question ( in cpx_lp form )
> ==================== > Minimize > obj: + 0.191747629717657 x_1 + x_3 > Subject To > r_1: + x_2 - x_1 = 2 > r_2: + x_3 + 0.216119012198317 x_2 >= 0.432238024396634 > Bounds > 0 <= x_1 <= 1 > -1 <= x_2 <= 2 > x_3 free > > End > ================ > The row dual value for r_1 is 0, for which I have a question. > In fact, when I change 2 to 1.99999, I get the dual value for r_1 is > -0.191748 which I want. Your lp has multiple optimal bases due to degeneracy. In one optimal basis the constraint r_1: + x_2 - x_1 = 2 is non-active, so the reduced cost of corresponding auxiliary (artificial) variable is zero. Changing 2 to 1.99999 perturbs the instance and removes the degeneracy (within a working precision). > I know there is no solution when RHS of r_1 bigger than 2. But I > am interested in the case that it is less than 2. > I want to know if there is a way to get -0.191748 without > changing the RHS value of r_1. All optimal bases are equivalent in the sense that they all are optimal. Why do you need to obtain a particular optimal basis? _______________________________________________ Help-glpk mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-glpk
