> I have a question concerning the difference between glpsol and the C-API > of glpk. > > The attached C source code file test.c contains a very tiny linear > optimization problem, the problem gets solved by glp_simplex and the > value of the objective function and of the primary variables after > optimization are printed out. Before the optimization, the problem will > be written to an lp file test.lp. > > Using this file with glpsol, gives another result than the C-API > (objective value stays the same, but the values of the variables differ > in some cases). > > glpsol --lp test.lp -o test.sol > > I am using glpk version 4.45 on debian wheezy (stable).
Please note that the most recent version is 4.53. > > Is there any explanation for this behavior? > This usually happens when the lp is dual degenerate, in which case it has multiple optima. (Imagine that the objective function is zero; then every feasible solution would be optimal.) If, for example, you don't use the lp presolver and/or scaling while glpsol does (by default), you may obtain different optimal solutions. _______________________________________________ Help-glpk mailing list [email protected] https://lists.gnu.org/mailman/listinfo/help-glpk
