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I'm trying to use the DFJ formulation to solve TSPLib problems using JuMP and Gurobi. I want to add a constraint to the starting point by fixing either the start or the end to the first node (because that's the assumption that TSPLib makes - at least for the symmetric TSP dataset). However, this results in an optimal solution not found, but removing this constraint yields a tour where the first node is visited in between the tour.

I wondering how one can add such a constraint to the DFJ formulation, if fixing values doesn't work.

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    $\begingroup$ Are you dealing with a classic TSP without further constraints such as time windows and time-dependent travel times? If that is the case, it would not matter which of the nodes is the depot, since you only want a cost-minimal tour. $\endgroup$
    – PeterD
    Feb 2 at 10:00
  • $\begingroup$ It's a constraint I want to place - that there is a depot/start point, but there are no delivery windows for any other node. I'll look into time windows - maybe that'll help me. $\endgroup$
    – skittish
    Feb 2 at 15:58
  • $\begingroup$ @skittish, welcome to OR.SE. One possible option would be to change a classic VRP problem in which the depot being as a starting point and you have one whole tour. $\endgroup$
    – A.Omidi
    Feb 2 at 21:01
  • $\begingroup$ Could you share some code snippet? $\endgroup$ Feb 13 at 12:20

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