Membuat kumpulan objek menggunakan ConcurrentBag
Contoh ini menunjukkan cara menggunakan ConcurrentBag<T> untuk mengimplementasikan kumpulan objek. Kumpulan objek dapat meningkatkan performa aplikasi dalam situasi di mana Anda memerlukan beberapa instans kelas dan kelas itu mahal untuk dibuat atau dihancurkan. Saat program klien meminta objek baru, kumpulan objek terlebih dahulu mencoba menyediakan objek yang telah dibuat dan dikembalikan ke kumpulan. Jika tidak ada yang tersedia, barulah objek baru dibuat.
ConcurrentBag<T> digunakan untuk menyimpan objek karena mendukung penyisipan dan penghapusan cepat, terutama ketika utas yang sama menambahkan dan menghapus item. Contoh ini dapat lebih ditingkatkan untuk dibangun di sekitar IProducerConsumerCollection<T>, yang diimplementasikan oleh struktur data bag, seperti halnya ConcurrentQueue<T> dan ConcurrentStack<T>.
Tip
Artikel ini mendefinisikan cara menulis sendiri implementasi kumpulan objek dengan jenis bersamaan yang mendasari guna menyimpan objek untuk digunakan kembali. Namun, jenis Microsoft.Extensions.ObjectPool.ObjectPool<T> sudah ada di bawah kumpulan nama XML Microsoft.Extensions.ObjectPool. Pertimbangkan untuk menggunakan jenis yang tersedia sebelum membuat implementasi Anda sendiri, yang menyertakan banyak fitur tambahan.
Contoh
using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;
namespace ObjectPoolExample
{
public class ObjectPool<T>
{
private readonly ConcurrentBag<T> _objects;
private readonly Func<T> _objectGenerator;
public ObjectPool(Func<T> objectGenerator)
{
_objectGenerator = objectGenerator ?? throw new ArgumentNullException(nameof(objectGenerator));
_objects = new ConcurrentBag<T>();
}
public T Get() => _objects.TryTake(out T item) ? item : _objectGenerator();
public void Return(T item) => _objects.Add(item);
}
class Program
{
static void Main(string[] args)
{
using var cts = new CancellationTokenSource();
// Create an opportunity for the user to cancel.
_ = Task.Run(() =>
{
if (char.ToUpperInvariant(Console.ReadKey().KeyChar) == 'C')
{
cts.Cancel();
}
});
var pool = new ObjectPool<ExampleObject>(() => new ExampleObject());
// Create a high demand for ExampleObject instance.
Parallel.For(0, 1000000, (i, loopState) =>
{
var example = pool.Get();
try
{
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($"{example.GetValue(i):####.####}");
}
finally
{
pool.Return(example);
}
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 ExampleObject
{
public int[] Nums { get; set; }
public ExampleObject()
{
Nums = new int[1000000];
var rand = new Random();
for (int i = 0; i < Nums.Length; i++)
{
Nums[i] = rand.Next();
}
}
public double GetValue(long i) => Math.Sqrt(Nums[i]);
}
}
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.Run(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()
cts.Dispose()
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
