Hello Florian, your problem is not trivial. Without an upper limit on the variables there is infinite number of solutions with allowable solution values ranging from 0 to infinity.
The following solves well: var x_1, integer, >=0, <= 10; var x_2, integer, >=0, <= 10; var x_3, integer, >=0, <= 10; var x_4, integer, >=0, <= 10; s.t. c1 : 1 <= 2*x_1 + 3*x_2 - 2*x_3 - 3*x_4; solve; end; --- The current version of GLPK is 4.47. GLPK 4.43 is available in Ubuntu 10.10 (Maverick), and Ubuntu 11.10 (Oneiric). Best regards Xypron -------- Original-Nachricht -------- > Datum: Tue, 01 Nov 2011 13:59:03 +0000 > Betreff: [Help-glpk] problem with simple MIP > Hello, > > I tried to use glpk to get a solution for the following almost trivial > MIP "feasibility" problem > > 1 <= 2*x_1 + 3*x_2 - 2*x_3 - 3*x_4 (x_i non-negative integers) > > but the solver didn't finish within 15h. Changing the coefficient of x_4 > from -3 to -1, -2, -4, or -5 gives (correct) solutions immediately. I'm > a bit puzzled now. It would be great if anyone could enlighten me? > > See below for more information. I'm happy to provide more details if > needed. > > Thanks, > Florian -- Follow me at http://twitter.com/#!/xypron NEU: FreePhone - 0ct/min Handyspartarif mit Geld-zurück-Garantie! Jetzt informieren: http://www.gmx.net/de/go/freephone _______________________________________________ Help-glpk mailing list [email protected] https://lists.gnu.org/mailman/listinfo/help-glpk
