0

我想模拟同时写入条件下stl map的异常行为。在这里，我使用单个映射并同时从多个线程插入数据。由于我们只使用一个地图对象，因此它不应该允许。请通过以下示例代码

    #include <iostream>
    #include <map>
    #include <iterator>
    #include <algorithm>

    extern "C"
    {
    #include <pthread.h>
    #include <string.h>
    #include <stdlib.h>
    }

    using namespace std;

//functor to print map
    struct PrintMp
    {
       void operator()(pair<int,int> pr)
       {
          cout<<pr.first<<" => "<<pr.second<<endl;
       }
    };
//thread 1
//inserts continuous no from 0 to 4999    
    void* ins_th1(void *arg)
    {
       map<int, int> *mp = static_cast<map<int, int>* >(arg);
       for(int i =0 ; i<5000; i++)
          mp->insert(pair<int,int>(i, i+1000));

       return NULL;
    }

//thread 1
//inserts continuous no from 0 to 4999    
    void* ins_th2(void *arg)
    {
       map<int, int> *mp = static_cast<map<int,int>* >(arg);
       for(int i=5000; i<10000; i++)
          mp->insert(pair<int, int>(i, i+2000));
       return NULL;
    }


    int main()
    {
       typedef map<int, int> IntMapType;

       IntMapType mp;
       PrintMp MpPrintObj;
       int rc;

       pthread_t th1, th2;
    //thread 1 creation
       rc = pthread_create(&th1, NULL, ins_th1, static_cast<void*>(&mp));
       if ( rc != 0)
       {
          cerr<<strerror(rc)<<"in thread1"<<endl;
          exit(EXIT_FAILURE);
       }
    //thread 2 creation
       rc = pthread_create(&th2, NULL, ins_th2, static_cast<void*>(&mp));
       if(rc!=0)
       {
          cerr<<strerror(rc)<<"in thread2"<<endl;
          exit(EXIT_FAILURE);
       }
    //lets wait for the thread to finish
       rc = pthread_join(th1, NULL);
       if ( rc != 0)
       {
          cerr<<strerror(rc)<<"join failure for thread1"<<endl;
          exit(EXIT_FAILURE);
       }

       rc = pthread_join(th2, NULL);
       if ( rc != 0)
       {
          cerr<<strerror(rc)<<"join failure for thread2"<<endl;
          exit(EXIT_FAILURE);
       }

       cout<<"Map data"<<endl;
    //now print it
       for_each(mp.begin(), mp.end(), MpPrintObj);
       cout<<endl;

       return 0;
    }

但它不起作用。谁能建议我一些方法？

4

2 回答 2

1

You are only testing insertion, which may or may not be implemented in a thread safe fashion, for all you know. But, your test is not complete. Allow the threads to write the same key into the map, and you will likely experience an error that would not happen without multiple threads.

   // ins_th1
   for(int i =0 ; i<10000; i++)
      mp->insert(pair<int,int>(i, i+1000));

   // ins_th2
   for(int i=0; i<10000; i++)
      mp->insert(pair<int, int>(i, i+2000));

You should test deletion from the map as well. When I modified your program to populate the map, before launching the threads, and only had the threads remove things from the map, the program live-locked.

   // ins_th1
   for(int i =0 ; i<5000; i++)
      mp->erase(i);

   // ins_th2
   for(int i=5000; i<10000; i++)
      mp->erase(i);

   // near top of main
   for(int i =0 ; i<5000; i++)
      mp.insert(pair<int,int>(i, i+1000));
   for(int i=5000; i<10000; i++)
      mp.insert(pair<int, int>(i, i+2000));
   //... launch threads
于 2012-07-20T21:56:14.703 回答
0

我试着按照你说的实施。

但是尽管没有使用任何同步机制，但我得到了完美的结果。

于 2012-07-27T21:21:19.317 回答