Hello, i cant add this subtour eliminattion to the gams code.
Any help is needed thanks
You are correct. It’s not possible to encode it as written because that SEC applies to every subset S of the node set N.
Instead, consider using the method in Ahuja’s textbook (see the TSP model), MTZ SECs, or one of the variants of the latter.
İ dont kno how i can coonvert it can you help ?
It’s not a conversion. They are alternatives. You need to read the text by Ahuja (1993), read a published article on MTZ constraints, or read one of the articles on MTZ enhancements. The three articles below are a starting point for your research.
Laporte, G. (1986). Generalized subtour elimination constraints and connectivity constraints. Journal of the Operational Research Society, 37(5), 509-514.
Desrochers, M., & Laporte, G. (1991). Improvements and extensions to the Miller-Tucker-Zemlin subtour elimination constraints. Operations Research Letters, 10(1), 27-36.
Bektaş, T., & Gouveia, L. (2014). Requiem for the Miller–Tucker–Zemlin subtour elimination constraints?. European Journal of Operational Research, 236(3), 820-832.