Elimination constraint & subset usage

[Ebru]

Hello guys,

I'm working on a vehicle routing problem. I was able to code the model somehow and got a result. But the results are undesirable sub-tours. I want to add sub-tour elimination constraints. An example is available below:

image.png (6.36 KiB) Viewed 2577 times

I have 15 stops and that means I add this constraint for 2**15 subsets. How can I generate sets of subtours and process this equation for each sub-set. Can you help me?

[bussieck]

Either use the compact Miller, Tucker and Zemlin formulation to avoid subtours or build up only the necessary subtour elimination constraints. Both are done here: https://www.gams.com/latest/gamslib_ml/ ... _tsp5.html

-Michael