Solving the model

Prerequisites

• Model-Class created
• Solver configured

Create Method to solve the model

This step will introduce a simple model runner.

1. first of all, the data of the model will be created and stored into the list of nodes and edges.
2. A OPTANO.Modeling.Optimization.Configuration is used to populate a ModelScope (the configuration of OPTANO.Model)
3. the actual Model is generated from the data, the OPTANO.Modeling.Optimization.Configuration may affect the model generation, f.e. by the parameter EnableFullNames (default: @false), which might save memory and shorten all Names.
4. A OPTANO.Modeling.Optimization.Solver in instanciated and used to solve the model. Solve returns a Solution, describing the solution status and the resulting variable values (decisions).
   • Note: It is advised to put a using-block around the Solver object. That way, the program will automatically release resources, such as license tokens, that are allocated by the solver, once the using-block is left.
5. the solution values are copied into the model (business layer).

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using OPTANO.Modeling.Optimization.Solver.Gurobi810;

namespace NDP
{
    using OPTANO.Modeling.Common;
    using OPTANO.Modeling.Optimization;
    using OPTANO.Modeling.Optimization.Configuration;
    using OPTANO.Modeling.Optimization.Solver.Gurobi810;

    /// <summary>
    /// Demo program solving a network design problem
    /// </summary>
    class Program
    {
        /// <summary>
        /// The main method
        /// </summary>
        /// <param name="args">
        /// no arguments required
        /// </param>
        static void Main(string[] args)
        {

            // create example Nodes
            INode pb = new Node("Paderborn", 50);
            INode ny = new Node("New York", -100);
            INode b = new Node("Beijing", 50);
            INode sp = new Node("São Paulo", 50);
            INode sf = new Node("San Francisco", -50);
            // assign these nodes to a list of INodes
            var nodes = new List<INode> { pb, ny, b, sp, sf };

            // create example Edges
            IEdge one = new Edge(ny, pb, null, 3, 6100);
            IEdge two = new Edge(b, ny, null, 2, 11000);
            IEdge three = new Edge(sp, b, 75, 1, 17600);
            IEdge four = new Edge(sf, sp, null, 4, 10500);
            IEdge five = new Edge(sp, pb, null, 5, 9900);
            IEdge six = new Edge(pb, b, 50, 1, 7600);

            // assign these edges to a list of IEdges
            var edges = new List<IEdge> { one, two, three, four, five, six };

            // Use long names for easier debugging/model understanding.
            var config = new Configuration();
            config.NameHandling = NameHandlingStyle.UniqueLongNames;
            config.ComputeRemovedVariables = true;
            using (var scope = new ModelScope(config))
            {
                // create a model, based on given data and the model scope
                var designModel = new NetworkDesignModel(nodes, edges);

                // Get a solver instance, change your solver
                using (var solver = new GurobiSolver())
                {
                    // solve the model
                    var solution = solver.Solve(designModel.Model);

                    // import the results back into the model 
                    designModel.Model.VariableCollections.ForEach(vc => vc.SetVariableValues(solution.VariableValues));

                    // print objective and variable decisions
                    Console.WriteLine($"{solution.ObjectiveValues.Single()}");
                    designModel.x.Variables.ForEach(x => Console.WriteLine($"{x.ToString().PadRight(36)}: {x.Value}"));
                    designModel.y.Variables.ForEach(y => Console.WriteLine($"{y.ToString().PadRight(36)}: {y.Value}"));

                    designModel.Model.VariableStatistics.WriteCSV(AppDomain.CurrentDomain.BaseDirectory);
                    Console.ReadLine();
                }
            }
        }
    }
}

Next step

Go to Get the solution