Interlocked.Decrement メソッド

定義

分割不可能な操作として、指定した変数をデクリメントし、結果を格納します。Decrements a specified variable and stores the result, as an atomic operation.

オーバーロード

Decrement(Int32)

分割不可能な操作として、指定した変数をデクリメントし、結果を格納します。Decrements a specified variable and stores the result, as an atomic operation.

Decrement(Int64)

分割不可能な操作として、指定した変数をデクリメントしてその結果を格納します。Decrements the specified variable and stores the result, as an atomic operation.

Decrement(Int32)

分割不可能な操作として、指定した変数をデクリメントし、結果を格納します。Decrements a specified variable and stores the result, as an atomic operation.

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

パラメーター

location
Int32

値がデクリメントされる変数。The variable whose value is to be decremented.

戻り値

デクリメントされた値。The decremented value.

例外

location のアドレスは null ポインターです。The address of location is a null pointer.

次の例では、中間値を使用して1000の乱数を生成するために、0 ~ 1000 の範囲の乱数を指定する必要があるかどうかを判断します。The following example determines how many random numbers that range from 0 to 1,000 are required to generate 1,000 random numbers with a midpoint value. 中間値の数を追跡するために、変数 midpointCountは、ランダム数値ジェネレーターが中間値を返すたびに1000に設定され、デクリメントされます。To keep track of the number of midpoint values, a variable, midpointCount, is set equal to 1,000 and decremented each time the random number generator returns a midpoint value. 3つのスレッドが乱数を生成するため、Decrement(Int32) メソッドを呼び出して、複数のスレッドが同時に midpointCount 更新しないようにします。Because three threads generate the random numbers, the Decrement(Int32) method is called to ensure that multiple threads don't update midpointCount concurrently. また、ランダムな数値ジェネレーターを保護するためにロックが使用されています。また、CountdownEvent オブジェクトを使用して、Main メソッドが3つのスレッドの前に実行を終了しないようにしています。Note that a lock is also used to protect the random number generator, and that a CountdownEvent object is used to ensure that the Main method doesn't finish execution before the three threads.

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 (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

次の例は前の例と似ていますが、スレッドプロシージャの代わりに Task クラスを使用して、5万のランダムな中間整数を生成する点が異なります。The following example is similar to the previous one, except that it uses the Task class instead of a thread procedure to generate 50,000 random midpoint integers. この例では、ラムダ式によって GenerateNumbers のスレッドプロシージャが置き換えられ、Task.WaitAll メソッドを呼び出すと、CountdownEvent オブジェクトが不要になります。In this example, a lambda expression replaces the GenerateNumbers thread procedure, and the call to the Task.WaitAll method eliminates the need for the CountdownEvent object.

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 (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

注釈

このメソッドは、をラップすることによってオーバーフロー状態を処理します。 location = Int32.MinValuelocation-1 = Int32.MaxValueです。This method handles an overflow condition by wrapping: If location = Int32.MinValue, location - 1 = Int32.MaxValue. 例外をスローすることはありません。No exception is thrown.

こちらもご覧ください

Decrement(Int64)

分割不可能な操作として、指定した変数をデクリメントしてその結果を格納します。Decrements the specified variable and stores the result, as an atomic operation.

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

パラメーター

location
Int64

値がデクリメントされる変数。The variable whose value is to be decremented.

戻り値

デクリメントされた値。The decremented value.

例外

location のアドレスは null ポインターです。The address of location is a null pointer.

注釈

このメソッドは、をラップすることによってオーバーフロー状態を処理します。 location = Int64.MinValuelocation-1 = Int64.MaxValueです。This method handles an overflow condition by wrapping: if location = Int64.MinValue, location - 1 = Int64.MaxValue. 例外をスローすることはありません。No exception is thrown.

こちらもご覧ください

適用対象