Interlocked.Decrement 方法

定義

命名空間:: System.Threading

組件:: mscorlib.dll, System.Threading.dll

組件:: netstandard.dll, System.Threading.dll

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。

遞減指定變數並儲存結果，作為原子操作。

多載

名稱	Description
Decrement(Int64)	遞減指定的變數並將結果儲存為原子操作。
Decrement(Int32)	遞減指定變數並儲存結果，作為原子操作。
Decrement(UInt32)	遞減指定變數並儲存結果，作為原子操作。
Decrement(UInt64)	遞減指定變數並儲存結果，作為原子操作。

Decrement(Int64)

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

遞減指定的變數並將結果儲存為原子操作。

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

該變數的值要遞減。

傳回

Int64

遞減操作結束後，變數的值會立即出現。

例外狀況

ArgumentNullException

的 location 位址是一個 null 指標。

NullReferenceException

的 location 位址是一個 null 指標。

備註

此方法處理溢位條件時，會將包裹為：如果 location = Int64.MinValue， - location 1 = Int64.MaxValue。沒例外拋出。

另請參閱

適用於

Decrement(Int32)

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

來源:: Interlocked.CoreCLR.cs

遞減指定變數並儲存結果，作為原子操作。

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

該變數的值要遞減。

傳回

Int32

遞減操作結束後，變數的值會立即出現。

例外狀況

ArgumentNullException

的 location 位址是一個 null 指標。

NullReferenceException

的 location 位址是一個 null 指標。

範例

以下範例決定產生1,000個中點數的隨機數，需要多少個介於0到1,000的隨機數。為了記錄中點數的數量，會設定一個變數 midpointCount，等於 1,000，並在隨機數產生器回傳中點值時，變數會遞減。由於三個執行緒會產生隨機數，因此呼叫此 Decrement(Int32) 方法以確保多個執行緒不會同時更新 midpointCount 。請注意，鎖同時用於保護隨機數產生器，並 CountdownEvent 使用物件確保 Main 方法不會在三個執行緒完成前完成執行。

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

以下範例與前一個相似，但使用 Task 類別而非執行緒程序，產生 50,000 個隨機中點整數。在此範例中，lambda 運算式取代 GenerateNumbers 了執行緒程序，而呼叫該 Task.WaitAll 方法則消除了對物件 CountdownEvent 的需求。

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

此方法處理溢位條件時，會將：如果 location = Int32.MinValue， - location 1 = 。 Int32.MaxValue 沒例外拋出。

另請參閱

管理的執行緒
同步處理基本概觀

適用於

Decrement(UInt32)

來源:: Interlocked.cs

來源:: Interlocked.cs

來源:: Interlocked.cs

來源:: Interlocked.cs

來源:: Interlocked.cs

重要

此 API 不符合 CLS 規範。

遞減指定變數並儲存結果，作為原子操作。

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

該變數的值要遞減。

傳回

UInt32

遞減操作結束後，變數的值會立即出現。

屬性: CLSCompliantAttribute

例外狀況

NullReferenceException

的 location 位址是一個 null 指標。

適用於

Decrement(UInt64)

來源:: Interlocked.cs

來源:: Interlocked.cs

來源:: Interlocked.cs

來源:: Interlocked.cs

來源:: Interlocked.cs

重要

此 API 不符合 CLS 規範。

遞減指定變數並儲存結果，作為原子操作。

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

該變數的值要遞減。

傳回

UInt64

遞減操作結束後，變數的值會立即出現。

屬性: CLSCompliantAttribute

例外狀況

NullReferenceException

的 location 位址是一個 null 指標。

適用於

意見反應

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