Interlocked.Decrement 方法

參考

定義

命名空間:: System.Threading

組件:: System.Threading.dll

組件:: mscorlib.dll

組件:: netstandard.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

遞減特定變數並將結果儲存起來，成為不可部分完成的作業。

多載

Decrement(Int64)	遞減特定變數並將結果儲存起來，成為不可部分完成的作業。
Decrement(Int32)	遞減特定變數並將結果儲存起來，成為不可部分完成的作業。
Decrement(UInt32)	遞減特定變數並將結果儲存起來，成為不可部分完成的作業。
Decrement(UInt64)	遞減特定變數並將結果儲存起來，成為不可部分完成的作業。

Decrement(Int64)

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

遞減特定變數並將結果儲存起來，成為不可部分完成的作業。

public:
 static long Decrement(long % location);

public static long Decrement (ref long location);

static member Decrement : int64 -> int64

Public Shared Function Decrement (ByRef location As Long) As Long

參數

location: Int64

值會被遞減的變數。

傳回

Int64

在遞減作業完成之後，變數的值。

例外狀況

ArgumentNullException

location 的位址為 null 指標。

NullReferenceException

location 的位址為 null 指標。

備註

這個方法會包裝來處理溢位條件：如果 location = Int64.MinValue， location - 1 = 。 Int64.MaxValue 不會擲回任何例外狀況。

另請參閱

適用於

Decrement(Int32)

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

遞減特定變數並將結果儲存起來，成為不可部分完成的作業。

public:
 static int Decrement(int % location);

public static int Decrement (ref int location);

static member Decrement : int -> int

Public Shared Function Decrement (ByRef location As Integer) As Integer

參數

location: Int32

值會被遞減的變數。

傳回

Int32

在遞減作業完成之後，變數的值。

例外狀況

ArgumentNullException

location 的位址為 null 指標。

NullReferenceException

location 的位址為 null 指標。

範例

下列範例會決定從 0 到 1,000 的隨機數數目，才能產生具有中間點值的 1,000 個隨機數。為了追蹤中間點值的數目，變數 midpointCount會設定為等於1,000，並在每次隨機數產生器傳回中間點值時遞減。由於三個線程會產生隨機數， Decrement(Int32) 因此會呼叫方法，以確保多個線程不會同時更新 midpointCount 。請注意，鎖定也用來保護隨機數產生器，而且對象用來確保Main方法不會在三個CountdownEvent線程之前完成執行。

using System;
using System.Threading;

public class Example
{
   const int LOWERBOUND = 0;
   const int UPPERBOUND = 1001;
   
   static Object lockObj = new Object();
   static Random rnd = new Random();
   static CountdownEvent cte;
   
   static int totalCount = 0;
   static int totalMidpoint = 0;
   static int midpointCount = 10000;

   public static void Main()
   {
      cte = new CountdownEvent(1);
      // Start three threads. 
      for (int ctr = 0; ctr <= 2; ctr++) {
         cte.AddCount();
         Thread th = new Thread(GenerateNumbers);
         th.Name = "Thread" + ctr.ToString();
         th.Start();
      }
      cte.Signal();
      cte.Wait();
      Console.WriteLine();
      Console.WriteLine("Total midpoint values:  {0,10:N0} ({1:P3})",
                        totalMidpoint, totalMidpoint/((double)totalCount));
      Console.WriteLine("Total number of values: {0,10:N0}", 
                        totalCount);                  
   }

   private static void GenerateNumbers()
   {
      int midpoint = (UPPERBOUND - LOWERBOUND) / 2;
      int value = 0;
      int total = 0;
      int midpt = 0;
      
      do {
         lock (lockObj) {
            value = rnd.Next(LOWERBOUND, UPPERBOUND);
         }
         if (value == midpoint) { 
            Interlocked.Decrement(ref midpointCount);
            midpt++;
         }
         total++;    
      } while (Volatile.Read(ref midpointCount) > 0);
      
      Interlocked.Add(ref totalCount, total);
      Interlocked.Add(ref totalMidpoint, midpt);
      
      string s = String.Format("Thread {0}:\n", Thread.CurrentThread.Name) +
                 String.Format("   Random Numbers: {0:N0}\n", total) + 
                 String.Format("   Midpoint values: {0:N0} ({1:P3})", midpt, 
                               ((double) midpt)/total);
      Console.WriteLine(s);
      cte.Signal();
   }
}
// The example displays output like the following:
//       Thread Thread2:
//          Random Numbers: 3,204,021
//          Midpoint values: 3,156 (0.099 %)
//       Thread Thread0:
//          Random Numbers: 4,073,592
//          Midpoint values: 4,015 (0.099 %)
//       Thread Thread1:
//          Random Numbers: 2,828,192
//          Midpoint values: 2,829 (0.100 %)
//       
//       Total midpoint values:      10,000 (0.099 %)
//       Total number of values: 10,105,805

Imports System.Threading

Module Example
   Const LOWERBOUND As Integer = 0
   Const UPPERBOUND As Integer = 1001
   
   Dim lockObj As New Object()
   Dim rnd As New Random()
   Dim cte As CountdownEvent
   
   Dim totalCount As Integer = 0
   Dim totalMidpoint As Integer = 0
   Dim midpointCount As Integer = 10000

   Public Sub Main()
      cte = New CountdownEvent(1)
      ' Start three threads. 
      For ctr As Integer = 0 To 2
         cte.AddCount()
         Dim th As New Thread(AddressOf GenerateNumbers)
         th.Name = "Thread" + ctr.ToString()
         th.Start()
      Next
      cte.Signal()
      cte.Wait()
      Console.WriteLine()
      Console.WriteLine("Total midpoint values:  {0,10:N0} ({1:P3})",
                        totalMidpoint, totalMidpoint/totalCount)
      Console.WriteLine("Total number of values: {0,10:N0}", 
                        totalCount)                  
   End Sub
   
   Private Sub GenerateNumbers()
      Dim midpoint As Integer = (upperBound - lowerBound) \ 2
      Dim value As Integer = 0
      Dim total As Integer = 0
      Dim midpt As Integer = 0
      Do
         SyncLock lockObj
            value = rnd.Next(lowerBound, upperBound)
         End SyncLock
         If value = midpoint Then 
            Interlocked.Decrement(midpointCount)
            midpt += 1
         End If
         total += 1    
      Loop While midpointCount > 0
      
      Interlocked.Add(totalCount, total)
      Interlocked.Add(totalMidpoint, midpt)
      
      Dim s As String = String.Format("Thread {0}:", Thread.CurrentThread.Name) + vbCrLf +
                        String.Format("   Random Numbers: {0:N0}", total) + vbCrLf +
                        String.Format("   Midpoint values: {0:N0} ({1:P3})", midpt, midpt/total)
      Console.WriteLine(s)
      cte.Signal()
   End Sub
End Module
' The example displays output like the following:
'       Thread Thread2:
'          Random Numbers: 3,204,021
'          Midpoint values: 3,156 (0.099 %)
'       Thread Thread0:
'          Random Numbers: 4,073,592
'          Midpoint values: 4,015 (0.099 %)
'       Thread Thread1:
'          Random Numbers: 2,828,192
'          Midpoint values: 2,829 (0.100 %)
'       
'       Total midpoint values:      10,000 (0.099 %)
'       Total number of values: 10,105,805

下列範例與上一個範例類似，不同之處在於它會使用 Task 類別而非線程程式來產生 50,000 個隨機中間點整數。在此範例中，Lambda 表達式會 GenerateNumbers 取代線程程式，而對方法的 Task.WaitAll 呼叫則 CountdownEvent 不需要物件。

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   const int LOWERBOUND = 0;
   const int UPPERBOUND = 1001;
   
   static Object lockObj = new Object();
   static Random rnd = new Random();
   
   static int totalCount = 0;
   static int totalMidpoint = 0;
   static int midpointCount = 50000;

   public static async Task Main()
   {
      List<Task> tasks = new List<Task>();

      // Start three tasks. 
      for (int ctr = 0; ctr <= 2; ctr++) 
         tasks.Add(Task.Run( () => { int midpoint = (UPPERBOUND - LOWERBOUND) / 2;
                                     int value = 0;
                                     int total = 0;
                                     int midpt = 0;
      
                                     do {
                                        lock (lockObj) {
                                           value = rnd.Next(LOWERBOUND, UPPERBOUND);
                                        }
                                        if (value == midpoint) { 
                                           Interlocked.Decrement(ref midpointCount);
                                           midpt++;
                                        }
                                        total++;    
                                     } while (Volatile.Read(ref midpointCount) > 0);
                                          
                                     Interlocked.Add(ref totalCount, total);
                                     Interlocked.Add(ref totalMidpoint, midpt);
                                          
                                     string s = String.Format("Task {0}:\n", Task.CurrentId) +
                                                String.Format("   Random Numbers: {0:N0}\n", total) + 
                                                String.Format("   Midpoint values: {0:N0} ({1:P3})", midpt, 
                                                              ((double) midpt)/total);
                                     Console.WriteLine(s); 
                                   } ));

      await Task.WhenAll(tasks.ToArray());

      Console.WriteLine();
      Console.WriteLine("Total midpoint values:  {0,10:N0} ({1:P3})",
                        totalMidpoint, totalMidpoint/((double)totalCount));
      Console.WriteLine("Total number of values: {0,10:N0}", 
                        totalCount);                  
   }
}
// The example displays output like the following:
//       Task 1:
//          Random Numbers: 24,530,624
//          Midpoint values: 24,675 (0.101 %)
//       Task 2:
//          Random Numbers: 7,079,718
//          Midpoint values: 7,093 (0.100 %)
//       Task 3:
//          Random Numbers: 18,284,617
//          Midpoint values: 18,232 (0.100 %)
//       
//       Total midpoint values:      50,000 (0.100 %)
//       Total number of values: 49,894,959

Imports System.Collections.Generic
Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Const LOWERBOUND As Integer = 0
   Const UPPERBOUND As Integer = 1001
   
   Dim lockObj As New Object()
   Dim rnd As New Random()
   
   Dim totalCount As Integer = 0
   Dim totalMidpoint As Integer = 0
   Dim midpointCount As Integer = 50000

   Public Sub Main()
      Dim tasks As New List(Of Task)()

      ' Start three tasks. 
      For ctr As Integer = 0 To 2
         tasks.Add( Task.Run(Sub() 
                                Dim midpoint As Integer = (upperBound - lowerBound) \ 2
                                Dim value As Integer = 0
                                Dim total As Integer = 0
                                Dim midpt As Integer = 0
                                Do
                                   SyncLock lockObj
                                      value = rnd.Next(lowerBound, upperBound)
                                   End SyncLock
                                   If value = midpoint Then 
                                      Interlocked.Decrement(midpointCount)
                                      midpt += 1
                                   End If
                                   total += 1    
                                Loop While midpointCount > 0
                              
                                Interlocked.Add(totalCount, total)
                                Interlocked.Add(totalMidpoint, midpt)
                              
                                Dim s As String = String.Format("Task {0}:", Task.CurrentId) + vbCrLf +
                                                  String.Format("   Random Numbers: {0:N0}", total) + vbCrLf +
                                                  String.Format("   Midpoint values: {0:N0} ({1:P3})", midpt, midpt/total)
                                Console.WriteLine(s)
                             End Sub ))
      Next
      Task.WaitAll(tasks.ToArray())
      Console.WriteLine()
      Console.WriteLine("Total midpoint values:  {0,10:N0} ({1:P3})",
                        totalMidpoint, totalMidpoint/totalCount)
      Console.WriteLine("Total number of values: {0,10:N0}", 
                        totalCount)                  
   End Sub
End Module
' The example displays output like the following:
'       Task 1:
'          Random Numbers: 24,530,624
'          Midpoint values: 24,675 (0.101 %)
'       Task 2:
'          Random Numbers: 7,079,718
'          Midpoint values: 7,093 (0.100 %)
'       Task 3:
'          Random Numbers: 18,284,617
'          Midpoint values: 18,232 (0.100 %)
'       
'       Total midpoint values:      50,000 (0.100 %)
'       Total number of values: 49,894,959

備註

此方法會包裝來處理溢位條件：如果 location = Int32.MinValue， location - 1 = Int32.MaxValue 不會擲回任何例外狀況。

另請參閱

適用於

Decrement(UInt32)

來源:: Interlocked.cs

來源:: Interlocked.cs

來源:: Interlocked.cs

重要

此 API 不符合 CLS 規範。

遞減特定變數並將結果儲存起來，成為不可部分完成的作業。

public:
 static System::UInt32 Decrement(System::UInt32 % location);

[System.CLSCompliant(false)]
public static uint Decrement (ref uint location);

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

Public Shared Function Decrement (ByRef location As UInteger) As UInteger

參數

location: UInt32

值會被遞減的變數。

傳回

UInt32

在遞減作業完成之後，變數的值。

屬性: CLSCompliantAttribute

例外狀況

NullReferenceException

location 的位址為 null 指標。

適用於

Decrement(UInt64)

來源:: Interlocked.cs

來源:: Interlocked.cs

來源:: Interlocked.cs

重要

此 API 不符合 CLS 規範。

遞減特定變數並將結果儲存起來，成為不可部分完成的作業。

public:
 static System::UInt64 Decrement(System::UInt64 % location);

[System.CLSCompliant(false)]
public static ulong Decrement (ref ulong location);

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

Public Shared Function Decrement (ByRef location As ULong) As ULong

參數

location: UInt64

值會被遞減的變數。

傳回

UInt64

在遞減作業完成之後，變數的值。

屬性: CLSCompliantAttribute

例外狀況

NullReferenceException

location 的位址為 null 指標。

適用於

共用方式為

Interlocked.Decrement 方法

定義

多載

Decrement(Int64)

參數

傳回

例外狀況

備註

另請參閱

適用於

Decrement(Int32)

參數

傳回

例外狀況

範例

備註

另請參閱

適用於

Decrement(UInt32)

參數

傳回

例外狀況

適用於

Decrement(UInt64)

參數

傳回

例外狀況

適用於

其他資源