On Fri, 18 Sep 2009, Sam Seaver wrote: > I'm getting an "Problem has no feasible solution" error from my use of > GLPK. I have found I can solve this by relaxing the upper and lower > constraints I have on one column in my constraint matrix. > > The constraints are fixed and equal: > > Col Lower Upper > ATPM 8.39 8.39 > > and if I relax the constrains arbitrarily, and in a small manner so > that they are no longer equal, for example: > > Col Lower Upper > ATPM 8.389 8.39 > > Then glpk will return an optimal solution.
With what value for ATPM? > What I don't understand is why I should have to do this? Is it > related to the tolerance of glpk, in that the difference between the > upper and lower constraints must be more than 1e-6 or something like > that? GLPK does allow one to fix variables. I suspose it's *possible* that telling it a fixed "variable" is double bounded instead of fixed might cause it to do the wrong thing. Probably the difficulty is elsewhere. Is your problem almost infeasible? -- Michael [email protected] "Pessimist: The glass is half empty. Optimist: The glass is half full. Engineer: The glass is twice as big as it needs to be." _______________________________________________ Help-glpk mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-glpk
