OR-Tools C++ VRP solving from assignment with parameters problem

Question

I'm trying to solve a vehicle routing problem with an initial assignment, and it seems that either I'm doing something wrong with setting the search parameters, or the model reaches a local minimum and returns a solution before reaching my desired time limit.

I suspect the former of the two options, but I don't see what I should be doing differently.

Here is how I go about it.

const Assignment *initial_solution =
    routing.ReadAssignmentFromRoutes(initial_routes, false);

RoutingSearchParameters searchParameters;
searchParameters.set_local_search_metaheuristic(
    LocalSearchMetaheuristic::GUIDED_LOCAL_SEARCH);
searchParameters.mutable_time_limit()->set_seconds(600);
searchParameters.set_log_search(true);

const Assignment *solution = routing.SolveFromAssignmentWithParameters(initial_solution, searchParameters);

where initial_routes is a valid route.

I would hugely appreciate if anyone could give me any pointers as to what I'm doing wrong.

Edit 1: Following Laurent's suggestion, I tried:

RoutingSearchParameters searchParameters;
searchParameters.set_local_search_metaheuristic(
    LocalSearchMetaheuristic::GUIDED_LOCAL_SEARCH);
searchParameters.mutable_time_limit()->set_seconds(600);
searchParameters.set_log_search(true);
    
routing.CloseModelWithParameters(searchParameters);

const Assignment *solution = 
    routing.Solve(initial_solution);

(Also tried with SolveFromAssignmentWithParameters with the same results)

Which gives me a following message preceeding a Segmentation fault Invalid RoutingSearchParameters: local_search_neighborhood_operator.use_relocate should be set to BOOL_TRUE or BOOL_FALSE instead of BOOL_UNSPECIFIED (value: 0)

I tried to find the particular option, but the only mention of use_relocate that I found was for RoutingSearchParameters_LocalSearchNeighborhoodOperators type object.

So then I tried to initialize the searchParameters to the default search parameters, but they once again seem to not get registered. Instead, I get a warning about the model already being closed.

Thank you again for any ideas.

Edit 2: I found the github issue with the bug ( link ) and the problem turned out to be the order that I do the things in. Fixed following the issue solution, thanks again

Answer 1

Known bug. You need to close the model with the parameters before solving.

And you should use

search_parameters = DefaultRoutingSearchParameters();