using System;
using System.Collections.Generic;
using System.Linq;
using Optimizer;
using Optimizer.Objects;
using static Optimizer.Objects.Utils;
namespace XPRSexamples
{
/// <summary>This example demonstrates some modeling devices.</summary>
/// <remarks>
/// We model a very simple facility location problem: We have customers
/// and facilities. The constraints are:
/// - each customer must be served from exactly one facility
/// - customers can only be served from open facilities
/// - customer demand must be satisfied
/// - facility capacity must not be exceeded
///
/// We minimize the sum of transport cost (between customer and facility)
/// and the cost for opening a facility.
/// In this example data is kept in arrays.
/// </remarks>
internal class FacilityLocationArray
{
/// <summary>Customer description.</summary>
private sealed class Customer
{
/// <summary>Name of customer.</summary>
public readonly string Name;
/// <summary>Demand for customer.</summary>
public readonly double Demand;
public Customer(string name, double demand)
{
this.Demand = demand;
this.Name = name;
}
}
/// <summary>Facility descriptor.</summary>
private sealed class Facility
{
/// <summary>Name of facility.</summary>
public readonly string Name;
/// <summary>Capacity of facility.</summary>
public readonly double Capacity;
/// <summary>Cost for opening this facility.</summary>
public readonly double Cost;
public Facility(string name, double capacity, double cost)
{
this.Name = name;
this.Capacity = capacity;
this.Cost = cost;
}
}
/// <summary>Customers in this example.</summary>
private static readonly Customer[] customers = new Customer[] { new Customer("Customer 1", 80),
new Customer("Customer 2", 270), new Customer("Customer 3", 250) };
/// <summary>Facilities in this example.</summary>
private static readonly Facility[] facilities = new Facility[] { new Facility("Facility 1", 500, 1000),
new Facility("Facility 2", 500, 1000), new Facility("Facility 3", 500, 1000) };
/// <summary>Cost for transporting one unit between customer and facility.</summary>
private static readonly double[][] transportCost = new double[][] { new double[] { 4, 5, 6 }, new double[] { 6, 4, 3 },
new double[] { 9, 7, 4 } };
public static void Main(string[] args)
{
using (XpressProblem prob = new XpressProblem())
{
Variable[] y = prob.AddVariables(facilities.Length)
.WithType(ColumnType.Binary)
.WithName(f => facilities[f].Name)
.ToArray();
Variable[,] x = prob.AddVariables(facilities.Length, customers.Length)
.WithUB(Double.PositiveInfinity)
.WithName((f, c) => $"x[{facilities[f].Name},{customers[c].Name}")
.ToArray();
// for each customer c
// sum(f=1..m) x[f,c] = d
prob.AddConstraints(customers.Length, c => Sum(facilities.Length, f => x[f, c]) == customers[c].Demand);
// for each facility f
// sum(c=1..n) x[f,c] <= capacity[j] * y[f]
prob.AddConstraints(facilities.Length, f => Sum(customers.Length, c => x[f, c]) <= y[f] * facilities[f].Capacity);
// minimize sum(f=1..m) cost[f] * y[f] +
// sum(c=1..n) sum(f=1..m) cost[f,c] * x[f,c]
prob.SetObjective(Sum(Sum(facilities.Length, f => y[f] * facilities[f].Cost),
Sum(customers.Length, c => Sum(facilities.Length, f => x[f, c] * transportCost[f][c]))));
prob.WriteProb("facilitylocationarray.lp");
prob.Optimize();
if (prob.SolStatus != SolStatus.Optimal)
throw new Exception($"failed to optimize with status {prob.SolStatus}");
double[] sol = prob.GetSolution();
for (int f = 0; f < facilities.Length; ++f)
{
if (y[f].GetValue(sol) > 0.5)
{
Console.WriteLine($"Facility {facilities[f].Name} is open, serves");
for (int c = 0; c < customers.Length; ++c)
{
if (x[f, c].GetValue(sol) > 0.0)
Console.WriteLine($" {customers[c].Name}: {x[f, c].GetValue(sol)}");
}
}
}
}
}
}
}
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// (c) 2023-2025 Fair Isaac Corporation
using System;
using System.Linq;
using Optimizer;
using static Optimizer.Objects.Utils;
using Variable = Optimizer.Objects.Variable;
using XpressProblem = Optimizer.Objects.XpressProblem;
using Optimizer.Maps;
using System.Collections.Generic;
namespace XPRSexamples
{
/// <summary>Solve a facility location problem for which data is given as collections.</summary>
public class FacilityLocationCollection
{
/// <summary>Customer descriptor.</summary>
private sealed class Customer
{
/// <summary>Customer name.</summary>
public readonly String name;
/// <summary>Demand for this customer.</summary>
public readonly double demand;
public Customer(String name, double demand)
{
this.demand = demand;
this.name = name;
}
}
/// <summary>Facility descriptor.</summary>
private sealed class Facility
{
/// <summary>Facility name.</summary>
public readonly String name;
/// <summary>Capacity of this facility.</summary>
public readonly double capacity;
/// <summary>Cost for opening this facility.</summary>
public readonly double cost;
public Facility(String name, double capacity, double cost)
{
this.name = name;
this.capacity = capacity;
this.cost = cost;
}
}
/// <summary>The customers in this example.</summary>
private static readonly Customer[] customers = new Customer[]{
new Customer("Customer 1", 80),
new Customer("Customer 2", 270),
new Customer("Customer 3", 250)
};
/// <summary>The facilityies in this example.</summary>
private static readonly Facility[] facilities = new Facility[]{
new Facility("Facility 1", 500, 1000),
new Facility("Facility 2", 500, 1000),
new Facility("Facility 3", 500, 1000)
};
/// <summary>Cost for transporting one unit between a customer and a facility.</summary>
private static readonly HashMap2<Facility, Customer, double> transportCost = new HashMap2<Facility, Customer, double>();
static FacilityLocationCollection()
{
transportCost.Add(facilities[0], customers[0], 4.0);
transportCost.Add(facilities[0], customers[1], 5.0);
transportCost.Add(facilities[0], customers[2], 6.0);
transportCost.Add(facilities[1], customers[0], 6.0);
transportCost.Add(facilities[1], customers[1], 4.0);
transportCost.Add(facilities[1], customers[2], 3.0);
transportCost.Add(facilities[2], customers[0], 9.0);
transportCost.Add(facilities[2], customers[1], 7.0);
transportCost.Add(facilities[2], customers[2], 4.0);
}
public static void Main(String[] args)
{
using (XpressProblem prob = new XpressProblem())
{
// Create a 1-dimensional map of y variables, indexed by Facility instances.
var y = prob.AddVariables(facilities)
.WithType(ColumnType.Binary)
.WithName(f => f.name)
.ToMap();
// Create a 2-dimensional map of x variables, indexed by (Facility,Customer) pairs
var x = prob.AddVariables(facilities, customers)
.WithName((f, c) => String.Format("x[{0},{1}]", f.name, c.name))
.ToMap();
// for each customer c
// sum(f=1..m) x[f,c] = d
prob.AddConstraints(customers,
c => Sum(facilities, (Facility f) => x[f, c]).Eq(c.demand)
);
// for each facility f
// sum(c=1..n) x[f,c] <= capacity[j] * y[f]
prob.AddConstraints(facilities,
f => Sum(customers, (Customer c) => x[f, c]).Leq(y[f] * f.capacity)
);
// minimize sum(j=1..m) cost[j] * y[j] +
// sum(i=1..n) sum(j=1..m) cost[f,c] * x[f,c]
prob.SetObjective(Sum(Sum(facilities, (Facility f) => y[f] * f.cost),
Sum(customers,
(Customer c) => Sum(facilities, (Facility f) => x[f, c] * transportCost[f, c]))));
prob.WriteProb("facilitylocationcollection.lp", "l");
prob.Optimize("");
double[] sol = prob.GetSolution();
foreach (var f in facilities)
{
if (y[f].GetValue(sol) > 0.5)
{
Console.WriteLine("Facility " + f.name + " is open, serves");
foreach (var c in customers)
{
if (x[f, c].GetValue(sol) > 0.0)
Console.WriteLine(" " + c.name + ": " +
x[f, c].GetValue(sol));
}
}
}
}
}
}
}
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