You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 12 Next »

The root page 15DOTs60ia13:Tutorial could not be found in space 15.S60 SSIM: Software Tools for Operations Research.

Using CPLEX in TspIpSolver

First, we need to set up the objective and the degree constraints. First, add the following fields to the class

private IloCplex cplex;
private TspInstance<V,E> tspInstance;
private final ImmutableBiMap<E,IloIntVar> edgeVariables;

and initialize them, as below.

	public TspIpSolver(TspInstance<V,E> tspInstance, EnumSet<Option> options) throws IloException{
		this.options = options;
		this.tspInstance = tspInstance;
		this.cplex = new IloCplex();
		UndirectedGraph<V,E> graph = tspInstance.getGraph(); //for convenience, we will be using this a lot
		this.edgeVariables = Util.makeBinaryVariables(cplex, graph.getEdges());
		//the degree constraints
		//the objective		
	}

The constraints and objective still need to be added to the cplex object. Try adding them yourself! The following methods (as defined in the previous 3 pages) should be useful for making the constraints:

  • From Util, the static method integerSum(IloCplex cplex, BiMap<T,IloIntVar> variables, Iterable<T> set)
  • From IloCplex, the method addEq(IloNumExpr e, double v)
  • From UndirectedGraph<V,E>, the method getIncidentEdges(V vertex)

If you are unfamiliar with Java, consider viewing the solution for the constraint, then trying the objective yourself.
Solution

For the objective, we need the functions:

  • From Util, the static method sum(IloCplex cplex, BiMap<T,IloIntVar> variables, Iterable<T> set, Function<? super T,? extends Number> coefficients)
  • From UndirectedGraph<V,E>, the method getEdges()
  • From TspInstance, the method getEdgeWeights

Solution

  • No labels