Cómo: Crear un grupo de objetos usando ConcurrentBag
En este ejemplo se muestra cómo usar un contenedor simultáneo para implementar un grupo de objetos. Los grupos de objetos pueden mejorar el rendimiento de la aplicación en situaciones donde se necesitan varias instancias de una clase y es costoso crear o destruir la clase. Cuando un programa cliente solicita un objeto nuevo, el grupo de objetos intenta primero proporcionar uno que ya se haya creado y devuelto ya al grupo. Si no hay ninguno disponible, solo entonces se crea un objeto nuevo.
ConcurrentBag<T> se emplea para almacenar los objetos porque admite la inserción y la eliminación rápidas, sobre todo cuando el mismo subproceso agrega y quita elementos. Este ejemplo podría ampliarse más alrededor de IProducerConsumerCollection<T>, que la estructura de datos de contenedor implementa, al igual que ConcurrentQueue<T> y ConcurrentStack<T>.
Ejemplo
Imports System
Imports System.Collections.Concurrent
Imports System.Threading
Imports System.Threading.Tasks
Module ObjectPoolExample
Public Class ObjectPool(Of T)
Private _objects As ConcurrentBag(Of T)
Private _objectGenerator As Func(Of T)
Public Sub New(ByVal objectGenerator As Func(Of T))
If objectGenerator Is Nothing Then Throw New ArgumentNullException("objectGenerator")
_objects = New ConcurrentBag(Of T)()
_objectGenerator = objectGenerator
End Sub
Public Function GetObject() As T
Dim item As T
If _objects.TryTake(item) Then Return item
Return _objectGenerator()
End Function
Public Sub PutObject(ByVal item As T)
_objects.Add(item)
End Sub
End Class
Sub Main()
Dim cts As CancellationTokenSource = New CancellationTokenSource()
' Create an opportunity for the user to cancel.
Task.Factory.StartNew(Sub()
If Console.ReadKey().KeyChar = "c"c Or Console.ReadKey().KeyChar = "C"c Then
cts.Cancel()
End If
End Sub)
Dim pool As ObjectPool(Of TestClass) = New ObjectPool(Of TestClass)(Function() New TestClass())
' Create a high demand for TestClass objects.
Parallel.For(0, 1000000, Sub(i, loopState)
Dim mc As TestClass = pool.GetObject()
Console.CursorLeft = 0
' This is the bottleneck in our application. All threads in this loop
' must serialize their access to the static Console class.
Console.WriteLine("{0:####.####}", mc.GetValue(i))
pool.PutObject(mc)
If cts.Token.IsCancellationRequested Then
loopState.Stop()
End If
End Sub)
Console.WriteLine("Press the Enter key to exit.")
Console.ReadLine()
End Sub
' A toy class that requires some resources to create.
' You can experiment here to measure the performance of the
' object pool vs. ordinary instantiation.
Class TestClass
Public Nums() As Integer
Public Function GetValue(ByVal i As Long) As Double
Return Math.Sqrt(Nums(i))
End Function
Public Sub New()
Nums = New Integer(10000000) {}
' ReDim Nums(1000000)
Dim rand As Random = New Random()
For i As Integer = 0 To Nums.Length - 1
Nums(i) = rand.Next()
Next
End Sub
End Class
End Module
using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;
namespace ObjectPoolExample
{
public class ObjectPool<T>
{
private ConcurrentBag<T> _objects;
private Func<T> _objectGenerator;
public ObjectPool(Func<T> objectGenerator)
{
if (objectGenerator == null) throw new ArgumentNullException("objectGenerator");
_objects = new ConcurrentBag<T>();
_objectGenerator = objectGenerator;
}
public T GetObject()
{
T item;
if (_objects.TryTake(out item)) return item;
return _objectGenerator();
}
public void PutObject(T item)
{
_objects.Add(item);
}
}
class Program
{
static void Main(string[] args)
{
CancellationTokenSource cts = new CancellationTokenSource();
// Create an opportunity for the user to cancel.
Task.Factory.StartNew(() =>
{
if (Console.ReadKey().KeyChar == 'c' || Console.ReadKey().KeyChar == 'C')
cts.Cancel();
});
ObjectPool<MyClass> pool = new ObjectPool<MyClass> (() => new MyClass());
// Create a high demand for MyClass objects.
Parallel.For(0, 1000000, (i, loopState) =>
{
MyClass mc = pool.GetObject();
Console.CursorLeft = 0;
// This is the bottleneck in our application. All threads in this loop
// must serialize their access to the static Console class.
Console.WriteLine("{0:####.####}", mc.GetValue(i));
pool.PutObject(mc);
if (cts.Token.IsCancellationRequested)
loopState.Stop();
});
Console.WriteLine("Press the Enter key to exit.");
Console.ReadLine();
}
}
// A toy class that requires some resources to create.
// You can experiment here to measure the performance of the
// object pool vs. ordinary instantiation.
class MyClass
{
public int[] Nums {get; set;}
public double GetValue(long i)
{
return Math.Sqrt(Nums[i]);
}
public MyClass()
{
Nums = new int[1000000];
Random rand = new Random();
for (int i = 0; i < Nums.Length; i++)
Nums[i] = rand.Next();
}
}
}