This example demonstrates how to use a GamsModelInstance to implement the sub tour elimination algorithm for the Traveling Salesman Problem (TSP) problem. More...

Variables
str	tsp.GAMS_MODEL

sys	tsp.sys_dir = sys.argv[1] if len(sys.argv) > 1 else None

GamsWorkspace	tsp.ws = GamsWorkspace(system_directory=sys_dir)

int	tsp.cuts_per_round = 10

int	tsp.cur_cut = 0

int	tsp.cmax = 0

GamsWorkspace	tsp.cut_data = ws.add_database()

GamsWorkspace	tsp.cc = cut_data.add_set("cc", 1)

GamsWorkspace	tsp.acut = cut_data.add_parameter("acut", 3)

GamsWorkspace	tsp.rhscut = cut_data.add_parameter("rhscut", 1)

list	tsp.n = []

GamsWorkspace	tsp.job = ws.add_job_from_string(GAMS_MODEL)

GamsWorkspace	tsp.cp = ws.add_checkpoint()

GamsWorkspace	tsp.opt = ws.add_options()

	tsp.gams_options

	tsp.checkpoint

GamsWorkspace	tsp.mi = cp.add_modelinstance()

GamsWorkspace	tsp.mi_acut = mi.sync_db.add_parameter("acut", 3)

GamsWorkspace	tsp.mi_rhscut = mi.sync_db.add_parameter("rhscut", 1)

dict	tsp.graph = {}

list	tsp.not_visited = list(n)

list	tsp.i = not_visited[0]

list	tsp.sub_tour = [i]

	tsp.value

	tsp.end

Detailed Description

This example demonstrates how to use a GamsModelInstance to implement the sub tour elimination algorithm for the Traveling Salesman Problem (TSP) problem.

Similar to benders_2stage.py example, we have a placeholder for the sub tour elimination constraint that gets generated in each iteration of the algorithm. In contrast to the Benders example, here we regenerate the GamsModelInstance if the original number of placeholders was not big enough. We continue this process until all sub tours are eliminated.

Definition in file tsp.py.

Variables

Detailed Description