Hi, Matthias Koeppe did a lot of work on MILPs recently, in particular on copying LPs, see e.g. http://trac.sagemath.org/ticket/20414 and the meta-ticket http://trac.sagemath.org/ticket/20302 Not sure whether he reads this, I cc to him. I presume you got one of these updates messing up your code. Dima
On Thursday, May 12, 2016 at 8:18:07 AM UTC+1, Martin R wrote: > > Hi there! > > I am having a severe problem with a program of mine that stopped working, > very likely after upgrading to 7.2.beta5, but I'm afraid I don't know from > which version. (I believe something after 7.1) > > The error I get is: > > ValueError: Variable MIPVariable of dimension 1 is a variable from a > different problem > > What I want to do is: check whether a MILP has a solution, and if so, > check whether it still has a solution if I add a further constraint. The > MILP's take a very long time to solve. > > What I do and what worked until very recently is roughly: > > p = MixedIntegerLinearProgram(constraint_generation=True, > solver="CPLEX") # solver="GLPK") # twice as long # > assignment = p.new_variable(binary=True) > > p.add_constraint(... some relations in terms of assignment[box, > colour] ... ) > > p.solve() > > for (box, colour) in large_list: > p_new = copy(p) > p_new.add_constraint(assignment[box, colour] == 0) > try: > p_new.solve() > > bang! > > What should I do? > > I don't have a minimal example exhibiting the error, but if absolutely > needed, I'd try to create one. > > Many thanks, > > Martin > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
