Interlocked.CompareExchange Metode

Definisi

Ruang nama:

System.Threading

Rakitan:

System.Threading.dll

Membandingkan dua nilai untuk kesetaraan dan, jika sama, menggantikan nilai pertama.

Overload

CompareExchange(UIntPtr, UIntPtr, UIntPtr)	Membandingkan dua handel atau pointer khusus platform untuk kesetaraan dan, jika sama, menggantikan yang pertama.
CompareExchange(UInt64, UInt64, UInt64)	Membandingkan dua bilangan bulat 64-bit yang tidak ditandatangani untuk kesetaraan dan, jika sama, menggantikan nilai pertama.
CompareExchange(UInt32, UInt32, UInt32)	Membandingkan dua bilangan bulat yang tidak ditandatangani 32-bit untuk kesetaraan dan, jika sama, menggantikan nilai pertama.
CompareExchange(Single, Single, Single)	Membandingkan dua angka titik float presisi tunggal untuk kesetaraan dan, jika sama, menggantikan nilai pertama.
CompareExchange(Object, Object, Object)	Membandingkan dua objek untuk kesetaraan referensi dan, jika sama, menggantikan objek pertama.
CompareExchange(Int64, Int64, Int64)	Membandingkan dua bilangan bulat bertanda 64-bit untuk kesetaraan dan, jika sama, menggantikan nilai pertama.
CompareExchange(Int32, Int32, Int32)	Membandingkan dua bilangan bulat bertanda tangan 32-bit untuk kesetaraan dan, jika sama, menggantikan nilai pertama.
CompareExchange(Double, Double, Double)	Membandingkan dua angka titik float presisi ganda untuk kesetaraan dan, jika sama, menggantikan nilai pertama.
CompareExchange(IntPtr, IntPtr, IntPtr)	Membandingkan dua handel atau pointer khusus platform untuk kesetaraan dan, jika sama, menggantikan yang pertama.
CompareExchange<T>(T, T, T)	Membandingkan dua instans dari jenis T referensi yang ditentukan untuk kesetaraan referensi dan, jika sama, menggantikan yang pertama.

CompareExchange(UIntPtr, UIntPtr, UIntPtr)

Sumber:

Interlocked.cs

Penting

API ini bukan kompatibel CLS.

Membandingkan dua handel atau pointer khusus platform untuk kesetaraan dan, jika sama, menggantikan yang pertama.

public:
 static UIntPtr CompareExchange(UIntPtr % location1, UIntPtr value, UIntPtr comparand);

[System.CLSCompliant(false)]
public static UIntPtr CompareExchange (ref UIntPtr location1, UIntPtr value, UIntPtr comparand);

[<System.CLSCompliant(false)>]
static member CompareExchange : unativeint * unativeint * unativeint -> unativeint

Public Shared Function CompareExchange (ByRef location1 As UIntPtr, value As UIntPtr, comparand As UIntPtr) As UIntPtr

Parameter

location1

UIntPtr

unativeint

Tujuan UIntPtr, yang nilainya dibandingkan dengan nilai comparand dan mungkin digantikan oleh value.

value

UIntPtr

unativeint

UIntPtr yang menggantikan nilai tujuan jika perbandingan menghasilkan kesetaraan.

comparand

UIntPtr

unativeint

UIntPtr yang dibandingkan dengan nilai di location1.

Mengembalikan

UIntPtr

unativeint

Nilai asli dalam location1.

Atribut

CLSCompliantAttribute

Pengecualian

NullReferenceException

Alamat location1 adalah null penunjuk.

CompareExchange(UInt64, UInt64, UInt64)

Sumber:

Interlocked.cs

Penting

API ini bukan kompatibel CLS.

Membandingkan dua bilangan bulat 64-bit yang tidak ditandatangani untuk kesetaraan dan, jika sama, menggantikan nilai pertama.

public:
 static System::UInt64 CompareExchange(System::UInt64 % location1, System::UInt64 value, System::UInt64 comparand);

[System.CLSCompliant(false)]
public static ulong CompareExchange (ref ulong location1, ulong value, ulong comparand);

[<System.CLSCompliant(false)>]
static member CompareExchange : uint64 * uint64 * uint64 -> uint64

Public Shared Function CompareExchange (ByRef location1 As ULong, value As ULong, comparand As ULong) As ULong

Parameter

location1

UInt64

Tujuan, yang nilainya dibandingkan dengan comparand dan mungkin diganti.

value

UInt64

Nilai yang menggantikan nilai tujuan jika perbandingan menghasilkan kesetaraan.

comparand

UInt64

Nilai yang dibandingkan dengan nilai di location1.

Mengembalikan

UInt64

Nilai asli dalam location1.

Atribut

CLSCompliantAttribute

Pengecualian

NullReferenceException

Alamat location1 adalah null penunjuk.

CompareExchange(UInt32, UInt32, UInt32)

Sumber:

Interlocked.cs

Penting

API ini bukan kompatibel CLS.

Membandingkan dua bilangan bulat yang tidak ditandatangani 32-bit untuk kesetaraan dan, jika sama, menggantikan nilai pertama.

public:
 static System::UInt32 CompareExchange(System::UInt32 % location1, System::UInt32 value, System::UInt32 comparand);

[System.CLSCompliant(false)]
public static uint CompareExchange (ref uint location1, uint value, uint comparand);

[<System.CLSCompliant(false)>]
static member CompareExchange : uint32 * uint32 * uint32 -> uint32

Public Shared Function CompareExchange (ByRef location1 As UInteger, value As UInteger, comparand As UInteger) As UInteger

Parameter

location1

UInt32

Tujuan, yang nilainya dibandingkan dengan comparand dan mungkin diganti.

value

UInt32

Nilai yang menggantikan nilai tujuan jika perbandingan menghasilkan kesetaraan.

comparand

UInt32

Nilai yang dibandingkan dengan nilai di location1.

Mengembalikan

UInt32

Nilai asli dalam location1.

Atribut

CLSCompliantAttribute

Pengecualian

NullReferenceException

Alamat location1 adalah null penunjuk.

CompareExchange(Single, Single, Single)

Sumber:

Interlocked.cs

Membandingkan dua angka titik float presisi tunggal untuk kesetaraan dan, jika sama, menggantikan nilai pertama.

public:
 static float CompareExchange(float % location1, float value, float comparand);

public static float CompareExchange (ref float location1, float value, float comparand);

static member CompareExchange : single * single * single -> single

Public Shared Function CompareExchange (ByRef location1 As Single, value As Single, comparand As Single) As Single

Parameter

location1

Single

Tujuan, yang nilainya dibandingkan dengan comparand dan mungkin diganti.

value

Single

Nilai yang menggantikan nilai tujuan jika perbandingan menghasilkan kesetaraan.

comparand

Single

Nilai yang dibandingkan dengan nilai di location1.

Mengembalikan

Single

Nilai asli dalam location1.

Pengecualian

NullReferenceException

Alamat adalah location1 penunjuk null.

Contoh

Contoh kode berikut menunjukkan metode thread-safe yang mengumpulkan total Single nilai yang sedang berjalan. Dua utas menambahkan serangkaian Single nilai menggunakan metode aman utas dan penambahan biasa, dan ketika utas menyelesaikan total dibandingkan. Pada komputer prosesor ganda, ada perbedaan signifikan dalam total.

Dalam metode thread-safe, nilai awal dari total yang berjalan disimpan, dan kemudian CompareExchange metode digunakan untuk menukar total yang baru dihitung dengan total lama. Jika nilai yang dikembalikan tidak sama dengan nilai tersimpan dari total yang berjalan, maka utas lain telah memperbarui total sementara itu. Dalam hal ini, upaya untuk memperbarui total yang sedang berjalan harus diulang.

// This example demonstrates a thread-safe method that adds to a
// running total.  
using System;
using System.Threading;

public class ThreadSafe
{
    // Field totalValue contains a running total that can be updated
    // by multiple threads. It must be protected from unsynchronized 
    // access.
    private float totalValue = 0.0F;

    // The Total property returns the running total.
    public float Total { get { return totalValue; }}

    // AddToTotal safely adds a value to the running total.
    public float AddToTotal(float addend)
    {
        float initialValue, computedValue;
        do
        {
            // Save the current running total in a local variable.
            initialValue = totalValue;

            // Add the new value to the running total.
            computedValue = initialValue + addend;

            // CompareExchange compares totalValue to initialValue. If
            // they are not equal, then another thread has updated the
            // running total since this loop started. CompareExchange
            // does not update totalValue. CompareExchange returns the
            // contents of totalValue, which do not equal initialValue,
            // so the loop executes again.
        }
        while (initialValue != Interlocked.CompareExchange(ref totalValue, 
            computedValue, initialValue));
        // If no other thread updated the running total, then 
        // totalValue and initialValue are equal when CompareExchange
        // compares them, and computedValue is stored in totalValue.
        // CompareExchange returns the value that was in totalValue
        // before the update, which is equal to initialValue, so the 
        // loop ends.

        // The function returns computedValue, not totalValue, because
        // totalValue could be changed by another thread between
        // the time the loop ends and the function returns.
        return computedValue;
    }
}

public class Test
{
    // Create an instance of the ThreadSafe class to test.
    private static ThreadSafe ts = new ThreadSafe();
    private static float control;

    private static Random r = new Random();
    private static ManualResetEvent mre = new ManualResetEvent(false);

    public static void Main()
    {
        // Create two threads, name them, and start them. The
        // thread will block on mre.
        Thread t1 = new Thread(TestThread);
        t1.Name = "Thread 1";
        t1.Start();
        Thread t2 = new Thread(TestThread);
        t2.Name = "Thread 2";
        t2.Start();

        // Now let the threads begin adding random numbers to 
        // the total.
        mre.Set();
        
        // Wait until all the threads are done.
        t1.Join();
        t2.Join();

        Console.WriteLine("Thread safe: {0}  Ordinary float: {1}", 
            ts.Total, control);
    }

    private static void TestThread()
    {
        // Wait until the signal.
        mre.WaitOne();

        for(int i = 1; i <= 1000000; i++)
        {
            // Add to the running total in the ThreadSafe instance, and
            // to an ordinary float.
            //
            float testValue = (float) r.NextDouble();
            control += testValue;
            ts.AddToTotal(testValue);
        }
    }
}

/* On a dual-processor computer, this code example produces output 
   similar to the following:

Thread safe: 17039.57  Ordinary float: 15706.44
 */

' This example demonstrates a thread-safe method that adds to a
' running total.  
Imports System.Threading

Public Class ThreadSafe
    ' Field totalValue contains a running total that can be updated
    ' by multiple threads. It must be protected from unsynchronized 
    ' access.
    Private totalValue As Single = 0.0

    ' The Total property returns the running total.
    Public ReadOnly Property Total As Single
        Get
            Return totalValue
        End Get
    End Property

    ' AddToTotal safely adds a value to the running total.
    Public Function AddToTotal(ByVal addend As Single) As Single
        Dim initialValue, computedValue As Single
        Do
            ' Save the current running total in a local variable.
            initialValue = totalValue

            ' Add the new value to the running total.
            computedValue = initialValue + addend

            ' CompareExchange compares totalValue to initialValue. If
            ' they are not equal, then another thread has updated the
            ' running total since this loop started. CompareExchange
            ' does not update totalValue. CompareExchange returns the
            ' contents of totalValue, which do not equal initialValue,
            ' so the loop executes again.
        Loop While initialValue <> Interlocked.CompareExchange( _
            totalValue, computedValue, initialValue)
        ' If no other thread updated the running total, then 
        ' totalValue and initialValue are equal when CompareExchange
        ' compares them, and computedValue is stored in totalValue.
        ' CompareExchange returns the value that was in totalValue
        ' before the update, which is equal to initialValue, so the 
        ' loop ends.

        ' The function returns computedValue, not totalValue, because
        ' totalValue could be changed by another thread between
        ' the time the loop ends and the function returns.
        Return computedValue
    End Function
End Class

Public Class Test
    ' Create an instance of the ThreadSafe class to test.
    Private Shared ts As New ThreadSafe()
    Private Shared control As Single

    Private Shared r As New Random()
    Private Shared mre As New ManualResetEvent(false)

    <MTAThread> _
    Public Shared Sub Main()
        ' Create two threads, name them, and start them. The
        ' threads will block on mre.
        Dim t1 As New Thread(AddressOf TestThread)
        t1.Name = "Thread 1"
        t1.Start()
        Dim t2 As New Thread(AddressOf TestThread)
        t2.Name = "Thread 2"
        t2.Start()

        ' Now let the threads begin adding random numbers to 
        ' the total.
        mre.Set()
        
        ' Wait until all the threads are done.
        t1.Join()
        t2.Join()

        Console.WriteLine("Thread safe: {0}  Ordinary Single: {1}", ts.Total, control)
    End Sub

    Private Shared Sub TestThread()
        ' Wait until the signal.
        mre.WaitOne()

        For i As Integer = 1 to 1000000
            ' Add to the running total in the ThreadSafe instance, and
            ' to an ordinary Single.
            '
            Dim testValue As Single = r.NextDouble()
            control += testValue
            ts.AddToTotal(testValue)
        Next
    End Sub
End Class

' On a dual-processor computer, this code example produces output 
' similar to the following:
'
'Thread safe: 17039.57  Ordinary Single: 15706.44

Keterangan

Jika comparand dan nilai di location1 sama, maka value disimpan dalam location1. Jika tidak, tidak ada operasi yang dilakukan. Operasi perbandingan dan pertukaran dilakukan sebagai operasi atomik. Nilai yang dikembalikan adalah CompareExchange nilai asli dalam location1, apakah pertukaran terjadi atau tidak.

Lihat juga

• Pengaluran Terkelola
• Ringkasan primitif sinkronisasi

CompareExchange(Object, Object, Object)

Sumber:

Interlocked.cs

Membandingkan dua objek untuk kesetaraan referensi dan, jika sama, menggantikan objek pertama.

public:
 static System::Object ^ CompareExchange(System::Object ^ % location1, System::Object ^ value, System::Object ^ comparand);

public static object? CompareExchange (ref object? location1, object? value, object? comparand);

static member CompareExchange : obj * obj * obj -> obj

Public Shared Function CompareExchange (ByRef location1 As Object, value As Object, comparand As Object) As Object

Parameter

location1

Object

Objek tujuan yang dibandingkan dengan referensi dengan comparand dan mungkin diganti.

value

Object

Objek yang menggantikan objek tujuan jika perbandingan referensi menghasilkan kesetaraan.

comparand

Object

Objek yang dibandingkan dengan referensi ke objek di location1.

Mengembalikan

Object

Nilai asli dalam location1.

Pengecualian

NullReferenceException

Alamat location1 adalah null penunjuk.

Keterangan

Penting

Dimulai dengan .NET Framework 2.0, CompareExchange<T>(T, T, T) metode kelebihan beban menyediakan alternatif yang aman untuk jenis referensi. Kami menyarankan agar Anda memanggilnya alih-alih kelebihan beban ini.

Jika comparand dan objek di location1 sama dengan referensi, maka value disimpan dalam location1. Jika tidak, tidak ada operasi yang dilakukan. Operasi perbandingan dan pertukaran dilakukan sebagai operasi atomik. Nilai yang dikembalikan adalah CompareExchange nilai asli dalam location1, apakah pertukaran terjadi atau tidak.

Catatan

Objek dibandingkan untuk kesetaraan referensi daripada kesetaraan nilai. Akibatnya, dua instans kotak dengan jenis nilai yang sama (misalnya, bilangan bulat 3) selalu tampak tidak sama dan tidak ada operasi yang dilakukan. Jangan gunakan kelebihan beban ini dengan jenis nilai.

Lihat juga

• Pengaluran Terkelola
• Ringkasan primitif sinkronisasi

CompareExchange(Int64, Int64, Int64)

Sumber:

Interlocked.cs

Membandingkan dua bilangan bulat bertanda 64-bit untuk kesetaraan dan, jika sama, menggantikan nilai pertama.

public:
 static long CompareExchange(long % location1, long value, long comparand);

public static long CompareExchange (ref long location1, long value, long comparand);

static member CompareExchange : int64 * int64 * int64 -> int64

Public Shared Function CompareExchange (ByRef location1 As Long, value As Long, comparand As Long) As Long

Parameter

location1

Int64

Tujuan, yang nilainya dibandingkan dengan comparand dan mungkin diganti.

value

Int64

Nilai yang menggantikan nilai tujuan jika perbandingan menghasilkan kesetaraan.

comparand

Int64

Nilai yang dibandingkan dengan nilai di location1.

Mengembalikan

Int64

Nilai asli dalam location1.

Pengecualian

NullReferenceException

Alamat adalah location1 penunjuk null.

Keterangan

Jika comparand dan nilai di location1 sama, maka value disimpan dalam location1. Jika tidak, tidak ada operasi yang dilakukan. Operasi perbandingan dan pertukaran dilakukan sebagai operasi atomik. Nilai yang dikembalikan adalah CompareExchange nilai asli dalam location1, apakah pertukaran terjadi atau tidak.

Lihat juga

• Pengaluran Terkelola
• Ringkasan primitif sinkronisasi

CompareExchange(Int32, Int32, Int32)

Sumber:

Interlocked.cs

Membandingkan dua bilangan bulat bertanda tangan 32-bit untuk kesetaraan dan, jika sama, menggantikan nilai pertama.

public:
 static int CompareExchange(int % location1, int value, int comparand);

public static int CompareExchange (ref int location1, int value, int comparand);

static member CompareExchange : int * int * int -> int

Public Shared Function CompareExchange (ByRef location1 As Integer, value As Integer, comparand As Integer) As Integer

Parameter

location1

Int32

Tujuan, yang nilainya dibandingkan dengan comparand dan mungkin diganti.

value

Int32

Nilai yang menggantikan nilai tujuan jika perbandingan menghasilkan kesetaraan.

comparand

Int32

Nilai yang dibandingkan dengan nilai di location1.

Mengembalikan

Int32

Nilai asli dalam location1.

Pengecualian

NullReferenceException

Alamat adalah location1 penunjuk null.

Contoh

Contoh kode berikut menunjukkan metode thread-safe yang mengumpulkan total yang sedang berjalan. Nilai awal dari total yang berjalan disimpan, lalu CompareExchange metode digunakan untuk menukar total yang baru dihitung dengan total lama. Jika nilai yang dikembalikan tidak sama dengan nilai tersimpan dari total yang berjalan, maka utas lain telah memperbarui total sementara itu. Dalam hal ini, upaya untuk memperbarui total yang sedang berjalan harus diulang.

Catatan

Metode iniAdd, yang diperkenalkan dalam versi 2.0 dari .NET Framework, menyediakan cara yang lebih nyaman untuk mengakumulasi total yang berjalan aman untuk bilangan bulat.

// This example demonstrates a thread-safe method that adds to a
// running total.  It cannot be run directly.  You can compile it
// as a library, or add the class to a project.
#using <system.dll>

using namespace System::Threading;
public ref class ThreadSafe
{
private:

   // totalValue contains a running total that can be updated
   // by multiple threads. It must be protected from unsynchronized 
   // access.
   int totalValue;

public:

   property int Total 
   {

      // The Total property returns the running total.
      int get()
      {
         return totalValue;
      }

   }

   // AddToTotal safely adds a value to the running total.
   int AddToTotal( int addend )
   {
      int initialValue;
      int computedValue;
      do
      {
         
         // Save the current running total in a local variable.
         initialValue = totalValue;
         
         // Add the new value to the running total.
         computedValue = initialValue + addend;
         
         // CompareExchange compares totalValue to initialValue. If
         // they are not equal, then another thread has updated the
         // running total since this loop started. CompareExchange
         // does not update totalValue. CompareExchange returns the
         // contents of totalValue, which do not equal initialValue,
         // so the loop executes again.
      }
      while ( initialValue != Interlocked::CompareExchange( totalValue, computedValue, initialValue ) );

      
      // If no other thread updated the running total, then 
      // totalValue and initialValue are equal when CompareExchange
      // compares them, and computedValue is stored in totalValue.
      // CompareExchange returns the value that was in totalValue
      // before the update, which is equal to initialValue, so the 
      // loop ends.
      // The function returns computedValue, not totalValue, because
      // totalValue could be changed by another thread between
      // the time the loop ends and the function returns.
      return computedValue;
   }

};

// This example demonstrates a thread-safe method that adds to a
// running total.  It cannot be run directly.  You can compile it
// as a library, or add the class to a project.
using System.Threading;

public class ThreadSafe {
    // totalValue contains a running total that can be updated
    // by multiple threads. It must be protected from unsynchronized 
    // access.
    private int totalValue = 0;

    // The Total property returns the running total.
    public int Total {
        get { return totalValue; }
    }

    // AddToTotal safely adds a value to the running total.
    public int AddToTotal(int addend) {
        int initialValue, computedValue;
        do {
            // Save the current running total in a local variable.
            initialValue = totalValue;

            // Add the new value to the running total.
            computedValue = initialValue + addend;

            // CompareExchange compares totalValue to initialValue. If
            // they are not equal, then another thread has updated the
            // running total since this loop started. CompareExchange
            // does not update totalValue. CompareExchange returns the
            // contents of totalValue, which do not equal initialValue,
            // so the loop executes again.
        } while (initialValue != Interlocked.CompareExchange(
            ref totalValue, computedValue, initialValue));
        // If no other thread updated the running total, then 
        // totalValue and initialValue are equal when CompareExchange
        // compares them, and computedValue is stored in totalValue.
        // CompareExchange returns the value that was in totalValue
        // before the update, which is equal to initialValue, so the 
        // loop ends.

        // The function returns computedValue, not totalValue, because
        // totalValue could be changed by another thread between
        // the time the loop ends and the function returns.
        return computedValue;
    }
}

' This example demonstrates a thread-safe method that adds to a
' running total.  It cannot be run directly.  You can compile it
' as a library, or add the class to a project.
Imports System.Threading

Public Class ThreadSafe
    ' Field totalValue contains a running total that can be updated
    ' by multiple threads. It must be protected from unsynchronized 
    ' access.
    Private totalValue As Integer = 0

    ' The Total property returns the running total.
    Public ReadOnly Property Total As Integer
        Get
            Return totalValue
        End Get
    End Property

    ' AddToTotal safely adds a value to the running total.
    Public Function AddToTotal(ByVal addend As Integer) As Integer
        Dim initialValue, computedValue As Integer
        Do
            ' Save the current running total in a local variable.
            initialValue = totalValue

            ' Add the new value to the running total.
            computedValue = initialValue + addend

            ' CompareExchange compares totalValue to initialValue. If
            ' they are not equal, then another thread has updated the
            ' running total since this loop started. CompareExchange
            ' does not update totalValue. CompareExchange returns the
            ' contents of totalValue, which do not equal initialValue,
            ' so the loop executes again.
        Loop While initialValue <> Interlocked.CompareExchange( _
            totalValue, computedValue, initialValue)
        ' If no other thread updated the running total, then 
        ' totalValue and initialValue are equal when CompareExchange
        ' compares them, and computedValue is stored in totalValue.
        ' CompareExchange returns the value that was in totalValue
        ' before the update, which is equal to initialValue, so the 
        ' loop ends.

        ' The function returns computedValue, not totalValue, because
        ' totalValue could be changed by another thread between
        ' the time the loop ends and the function returns.
        Return computedValue
    End Function
End Class

Keterangan

Jika comparand dan nilai di location1 sama, maka value disimpan dalam location1. Jika tidak, tidak ada operasi yang dilakukan. Operasi perbandingan dan pertukaran dilakukan sebagai operasi atomik. Nilai yang dikembalikan adalah CompareExchange nilai asli dalam location1, apakah pertukaran terjadi atau tidak.

Lihat juga

• Pengaluran Terkelola
• Ringkasan primitif sinkronisasi

CompareExchange(Double, Double, Double)

Sumber:

Interlocked.cs

Membandingkan dua angka titik float presisi ganda untuk kesetaraan dan, jika sama, menggantikan nilai pertama.

public:
 static double CompareExchange(double % location1, double value, double comparand);

public static double CompareExchange (ref double location1, double value, double comparand);

static member CompareExchange : double * double * double -> double

Public Shared Function CompareExchange (ByRef location1 As Double, value As Double, comparand As Double) As Double

Parameter

location1

Double

Tujuan, yang nilainya dibandingkan dengan comparand dan mungkin diganti.

value

Double

Nilai yang menggantikan nilai tujuan jika perbandingan menghasilkan kesetaraan.

comparand

Double

Nilai yang dibandingkan dengan nilai di location1.

Mengembalikan

Double

Nilai asli dalam location1.

Pengecualian

NullReferenceException

Alamat adalah location1 penunjuk null.

Contoh

Contoh kode berikut menunjukkan metode thread-safe yang mengumpulkan total Double nilai yang sedang berjalan. Dua utas menambahkan serangkaian Double nilai menggunakan metode aman utas dan penambahan biasa, dan ketika utas menyelesaikan total dibandingkan. Pada komputer prosesor ganda, ada perbedaan signifikan dalam total.

Dalam metode thread-safe, nilai awal dari total yang berjalan disimpan, dan kemudian CompareExchange metode digunakan untuk menukar total yang baru dihitung dengan total lama. Jika nilai yang dikembalikan tidak sama dengan nilai tersimpan dari total yang berjalan, maka utas lain telah memperbarui total sementara itu. Dalam hal ini, upaya untuk memperbarui total yang sedang berjalan harus diulang.

// This example demonstrates a thread-safe method that adds to a
// running total.  
using System;
using System.Threading;

public class ThreadSafe
{
    // Field totalValue contains a running total that can be updated
    // by multiple threads. It must be protected from unsynchronized 
    // access.
    private double totalValue = 0.0;

    // The Total property returns the running total.
    public double Total { get { return totalValue; }}

    // AddToTotal safely adds a value to the running total.
    public double AddToTotal(double addend)
    {
        double initialValue, computedValue;
        do
        {
            // Save the current running total in a local variable.
            initialValue = totalValue;

            // Add the new value to the running total.
            computedValue = initialValue + addend;

            // CompareExchange compares totalValue to initialValue. If
            // they are not equal, then another thread has updated the
            // running total since this loop started. CompareExchange
            // does not update totalValue. CompareExchange returns the
            // contents of totalValue, which do not equal initialValue,
            // so the loop executes again.
        }
        while (initialValue != Interlocked.CompareExchange(ref totalValue, 
            computedValue, initialValue));
        // If no other thread updated the running total, then 
        // totalValue and initialValue are equal when CompareExchange
        // compares them, and computedValue is stored in totalValue.
        // CompareExchange returns the value that was in totalValue
        // before the update, which is equal to initialValue, so the 
        // loop ends.

        // The function returns computedValue, not totalValue, because
        // totalValue could be changed by another thread between
        // the time the loop ends and the function returns.
        return computedValue;
    }
}

public class Test
{
    // Create an instance of the ThreadSafe class to test.
    private static ThreadSafe ts = new ThreadSafe();
    private static double control;

    private static Random r = new Random();
    private static ManualResetEvent mre = new ManualResetEvent(false);

    public static void Main()
    {
        // Create two threads, name them, and start them. The
        // thread will block on mre.
        Thread t1 = new Thread(TestThread);
        t1.Name = "Thread 1";
        t1.Start();
        Thread t2 = new Thread(TestThread);
        t2.Name = "Thread 2";
        t2.Start();

        // Now let the threads begin adding random numbers to 
        // the total.
        mre.Set();
        
        // Wait until all the threads are done.
        t1.Join();
        t2.Join();

        Console.WriteLine("Thread safe: {0}  Ordinary Double: {1}", 
            ts.Total, control);
    }

    private static void TestThread()
    {
        // Wait until the signal.
        mre.WaitOne();

        for(int i = 1; i <= 1000000; i++)
        {
            // Add to the running total in the ThreadSafe instance, and
            // to an ordinary double.
            //
            double testValue = r.NextDouble();
            control += testValue;
            ts.AddToTotal(testValue);
        }
    }
}

/* On a dual-processor computer, this code example produces output 
   similar to the following:

Thread safe: 998068.049623744  Ordinary Double: 759775.417190589
 */

' This example demonstrates a thread-safe method that adds to a
' running total.  
Imports System.Threading

Public Class ThreadSafe
    ' Field totalValue contains a running total that can be updated
    ' by multiple threads. It must be protected from unsynchronized 
    ' access.
    Private totalValue As Double = 0.0

    ' The Total property returns the running total.
    Public ReadOnly Property Total As Double
        Get
            Return totalValue
        End Get
    End Property

    ' AddToTotal safely adds a value to the running total.
    Public Function AddToTotal(ByVal addend As Double) As Double
        Dim initialValue, computedValue As Double
        Do
            ' Save the current running total in a local variable.
            initialValue = totalValue

            ' Add the new value to the running total.
            computedValue = initialValue + addend

            ' CompareExchange compares totalValue to initialValue. If
            ' they are not equal, then another thread has updated the
            ' running total since this loop started. CompareExchange
            ' does not update totalValue. CompareExchange returns the
            ' contents of totalValue, which do not equal initialValue,
            ' so the loop executes again.
        Loop While initialValue <> Interlocked.CompareExchange( _
            totalValue, computedValue, initialValue)
        ' If no other thread updated the running total, then 
        ' totalValue and initialValue are equal when CompareExchange
        ' compares them, and computedValue is stored in totalValue.
        ' CompareExchange returns the value that was in totalValue
        ' before the update, which is equal to initialValue, so the 
        ' loop ends.

        ' The function returns computedValue, not totalValue, because
        ' totalValue could be changed by another thread between
        ' the time the loop ends and the function returns.
        Return computedValue
    End Function
End Class

Public Class Test
    ' Create an instance of the ThreadSafe class to test.
    Private Shared ts As New ThreadSafe()
    Private Shared control As Double

    Private Shared r As New Random()
    Private Shared mre As New ManualResetEvent(false)

    <MTAThread> _
    Public Shared Sub Main()
        ' Create two threads, name them, and start them. The
        ' threads will block on mre.
        Dim t1 As New Thread(AddressOf TestThread)
        t1.Name = "Thread 1"
        t1.Start()
        Dim t2 As New Thread(AddressOf TestThread)
        t2.Name = "Thread 2"
        t2.Start()

        ' Now let the threads begin adding random numbers to 
        ' the total.
        mre.Set()
        
        ' Wait until all the threads are done.
        t1.Join()
        t2.Join()

        Console.WriteLine("Thread safe: {0}  Ordinary Double: {1}", ts.Total, control)
    End Sub

    Private Shared Sub TestThread()
        ' Wait until the signal.
        mre.WaitOne()

        For i As Integer = 1 to 1000000
            ' Add to the running total in the ThreadSafe instance, and
            ' to an ordinary double.
            '
            Dim testValue As Double = r.NextDouble
            control += testValue
            ts.AddToTotal(testValue)
        Next
    End Sub
End Class

' On a dual-processor computer, this code example produces output 
' similar to the following:
'
'Thread safe: 998068.049623744  Ordinary Double: 759775.417190589

Keterangan

Jika comparand dan nilai di location1 sama, maka value disimpan dalam location1. Jika tidak, tidak ada operasi yang dilakukan. Operasi perbandingan dan pertukaran dilakukan sebagai operasi atomik. Nilai yang dikembalikan adalah CompareExchange nilai asli dalam location1, apakah pertukaran terjadi atau tidak.

Lihat juga

• Pengaluran Terkelola
• Ringkasan primitif sinkronisasi

CompareExchange(IntPtr, IntPtr, IntPtr)

Sumber:

Interlocked.cs

Membandingkan dua handel atau pointer khusus platform untuk kesetaraan dan, jika sama, menggantikan yang pertama.

public:
 static IntPtr CompareExchange(IntPtr % location1, IntPtr value, IntPtr comparand);

public static IntPtr CompareExchange (ref IntPtr location1, IntPtr value, IntPtr comparand);

static member CompareExchange : nativeint * nativeint * nativeint -> nativeint

Public Shared Function CompareExchange (ByRef location1 As IntPtr, value As IntPtr, comparand As IntPtr) As IntPtr

Parameter

location1

IntPtr

nativeint

Tujuan IntPtr, yang nilainya dibandingkan dengan nilai comparand dan mungkin digantikan oleh value.

value

IntPtr

nativeint

IntPtr yang menggantikan nilai tujuan jika perbandingan menghasilkan kesetaraan.

comparand

IntPtr

nativeint

IntPtr yang dibandingkan dengan nilai di location1.

Mengembalikan

IntPtr

nativeint

Nilai asli dalam location1.

Pengecualian

NullReferenceException

Alamat adalah location1 penunjuk null.

Keterangan

Jika comparand dan nilai di location1 sama, maka value disimpan dalam location1. Jika tidak, tidak ada operasi yang dilakukan. Operasi perbandingan dan pertukaran dilakukan sebagai operasi atomik. Nilai yang dikembalikan dari metode ini adalah nilai asli dalam location1, apakah pertukaran terjadi atau tidak.

Catatan

IntPtr adalah jenis khusus platform.

Lihat juga

• Pengaluran Terkelola
• Ringkasan primitif sinkronisasi

CompareExchange<T>(T, T, T)

Sumber:

Interlocked.CoreCLR.cs

Membandingkan dua instans dari jenis T referensi yang ditentukan untuk kesetaraan referensi dan, jika sama, menggantikan yang pertama.

public:
generic <typename T>
 where T : class static T CompareExchange(T % location1, T value, T comparand);

public static T CompareExchange<T> (ref T location1, T value, T comparand) where T : class;

static member CompareExchange : 'T * 'T * 'T -> 'T (requires 'T : null)

Public Shared Function CompareExchange(Of T As Class) (ByRef location1 As T, value As T, comparand As T) As T

Jenis parameter

T

Jenis yang akan digunakan untuk location1, , valuedan comparand. Jenis ini harus berupa tipe referensi.

Parameter

location1

T

Tujuan, yang nilainya dibandingkan dengan referensi dengan comparand dan mungkin diganti. Ini adalah parameter referensi (ref dalam C#, ByRef di Visual Basic).

value

T

Nilai yang menggantikan nilai tujuan jika perbandingan dengan referensi menghasilkan kesetaraan.

comparand

T

Nilai yang dibandingkan dengan referensi ke nilai di location1.

Mengembalikan

T

Nilai asli dalam location1.

Pengecualian

NullReferenceException

Alamat adalah location1 penunjuk null.

Keterangan

Jika comparand dan nilai di location1 sama dengan referensi, maka value disimpan dalam location1. Jika tidak, tidak ada operasi yang dilakukan. Perbandingan dan pertukaran dilakukan sebagai operasi atomik. Nilai yang dikembalikan dari metode ini adalah nilai asli dalam location1, apakah pertukaran terjadi atau tidak.

Metode ini hanya mendukung jenis referensi. Ada kelebihan beban CompareExchange metode untuk jenis Int32nilai , , Int64, IntPtr, Singledan Double, tetapi tidak ada dukungan untuk jenis nilai lainnya.

Catatan

Metode ini kelebihan beban lebih disukai daripada CompareExchange(Object, Object, Object) metode kelebihan beban, karena yang terakhir mengharuskan objek tujuan diakses terlambat terikat.