使用 Vector 迭代器的多线程

发布于 2024-11-18 23:31:18 字数 664 浏览 3 评论 0原文

我已将向量声明为

typedef std::向量<无符号整数>样本列表；

并在类中声明了Samplist类型的成员变量。

我正在从另一个具有多个线程的类访问这个向量。

我正在添加、删除、读取来自不同线程的值。我经常阅读这个值，如下所示。

SampleList* listSample;
listSample= ptr->GetList();
while(true)
{   
    SampleList::iterator itrSample;
    itrSample = listSample->begin();

    unsigned int nId = 0;


    for ( ; itrSample < listRoundRobinSensor->end(); ++itrSample )
    {           
         nId =(unsigned int) *itrSample ;
    }

}

itrSample 的值变成垃圾值，如 4261281277。

我试图用关键部分来保护这个列表。我仍然遇到这个问题。您能提出建议和解决方案吗？这对我很有帮助。

原文

I 've declared a vector as

typedef std::vector< unsigned int > SampleList;

and declared Samplist type member variable in a class.

I am accessing this vector from another class with multiple threads.

I am adding , deleting , Reading values values from different threads. I am reading this value frequently like the following.

SampleList* listSample;
listSample= ptr->GetList();
while(true)
{   
    SampleList::iterator itrSample;
    itrSample = listSample->begin();

    unsigned int nId = 0;


    for ( ; itrSample < listRoundRobinSensor->end(); ++itrSample )
    {           
         nId =(unsigned int) *itrSample ;
    }

}

The value for itrSample becomes junk value like 4261281277.

I tried to guard this list with critical secion. Still I got this issue. Can you suggest and solution. It will be very helpful to me.

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凉风有信 2024-11-25 23:31:18

一旦有人添加或删除向量的成员，你的迭代器就会变得无效。

特别是如果添加元素，可能必须重新分配内部缓冲区。但如果对象被删除，end() 也会移动，您可能会错过它。

您必须有一个锁来在迭代向量时保护它。

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半世晨晓 2024-11-25 23:31:18

您能向我们展示您如何处理关键部分吗？因为 Mutex 绝对可以解决你的问题

然后，猜测一下，如果即使关键部分仍然存在问题，这可能是因为插入和删除使迭代器无效而发生的。

如果你这样做：

  ...
  {
    for ( ; itrSample < listRoundRobinSensor->end(); ++itrSample )
    {        
      MutexLocker m(mutex);   
      nId =(unsigned int) *itrSample ;
      // Do horrible stuff like insertion/deletion
    } // m dies at the end of the scope (cf RAII)
  }

那么，这会导致并发错误。 itrSample 变得无效。

解决方案是：

  ...
  {
    MutexLocker m(mutex);   
    for ( ; itrSample < listRoundRobinSensor->end(); ++itrSample )
    {   
      nId =(unsigned int) *itrSample ;
      // Do horrible stuff like insertion/deletion
    } 
  } // m dies at the end of the scope (cf RAII)

Can you show us how you do your critical sections? Because Mutex can definitely solve your problem

Then, a bit of guessing, if you still have issues even with critical sections, this might happen because insertion and deletion invalidates iterators.

if you do :

  ...
  {
    for ( ; itrSample < listRoundRobinSensor->end(); ++itrSample )
    {        
      MutexLocker m(mutex);   
      nId =(unsigned int) *itrSample ;
      // Do horrible stuff like insertion/deletion
    } // m dies at the end of the scope (cf RAII)
  }

then, this cause concurrent errors. itrSample becomes invalid.

A solution would be :

  ...
  {
    MutexLocker m(mutex);   
    for ( ; itrSample < listRoundRobinSensor->end(); ++itrSample )
    {   
      nId =(unsigned int) *itrSample ;
      // Do horrible stuff like insertion/deletion
    } 
  } // m dies at the end of the scope (cf RAII)

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