C++ 11线程：将向量传递给线程函数时出错

Question

我正在将多线程中值函数作为大型项目的一部分工作。我有一点C++经验。下面的中值函数应该采用3维向量的向量，并返回一个3维向量，其中每个条目是输入向量中该索引中所有条目的中值。所以如果输入是< < 3,2,1>，< 1,2,3>，< 2,2,2 >>，则返回< 2,2,2>。该代码将用于实现实时视频中的中值模糊，因此希望对其进行多线程处理。

#include <thread> 
#include <iostream> 
#include <mutex> 
#include <vector> 
#include <algorithm> 
#include "median.h" 

// mutex to protect bgrPixel (possibly not needed) 
std::mutex mtx; 


std::vector<int> median(const std::vector<std::vector<int> >& input) 
{ 
    std::vector<int> bgrPixel;    // Vector to store median BGR value 
    std::thread first(thread_function, bgrPixel, input, 0); // thread for each colour channel 
    std::thread second(thread_function, bgrPixel, input, 1); 
    std::thread third(thread_function, bgrPixel, input, 2); 
    first.join(); 
    second.join(); 
    third.join(); 
    return bgrPixel; 
} 

void thread_function(std::vector<int>& bgrPixel, const std::vector<std::vector<int> >&     input1, int channel) 
{ 

    std::vector<int> input = input1[channel]; // copy the colour channel 
    std::sort(input.begin(), input.end()); 
    int size = input.size(); 
    if (size %2 == 0) // get the median 
    { 
     mtx.lock(); 
     bgrPixel[channel] = (input[size/2] + input[size/2 + 1])/2; 
     mtx.unlock(); 
    } else 
    { 
     mtx.lock(); 
     bgrPixel[channel] = input[(size-1)/2]; 
     mtx.unlock(); 
    } 
} 

我遇到的问题是，在编译时，G ++（和铛也）给出一个相当难以理解的错误：

g++ -std=c++11 -pthread -o median median.cpp 

In file included from /usr/include/c++/4.8.2/thread:39:0, 
        from median.cpp:1: 
/usr/include/c++/4.8.2/functional: In instantiation of ‘struct std::_Bind_simple<void   (*(std::vector<int>, std::vector<std::vector<int> >, int))(std::vector<int>&, const  std::vector<std::vector<int> >&, int)>’: 
/usr/include/c++/4.8.2/thread:137:47: required from ‘std::thread::thread(_Callable&&,   _Args&& ...) [with _Callable = void (&)(std::vector<int>&, const  std::vector<std::vector<int> >&, int); _Args = {std::vector<int, std::allocator<int> >&,  const std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int,  std::allocator<int> > > >&, int}]’ 
median.cpp:15:58: required from here 
/usr/include/c++/4.8.2/functional:1697:61: error: no type named ‘type’ in ‘class    std::result_of<void (*(std::vector<int>, std::vector<std::vector<int> >, int))  (std::vector<int>&, const std::vector<std::vector<int> >&, int)>’ 
     typedef typename result_of<_Callable(_Args...)>::type result_type; 
                 ^
/usr/include/c++/4.8.2/functional:1727:9: error: no type named ‘type’ in ‘class  std::result_of<void (*(std::vector<int>, std::vector<std::vector<int> >, int))  (std::vector<int>&, const std::vector<std::vector<int> >&, int)>’ 
      _M_invoke(_Index_tuple<_Indices...>) 
     ^

我已发现类似的错误消息c++11 Thread class how to use a class member function，但它不会特别处理我的问题。 任何帮助将不胜感激，我完全期待这是因为我不知道我在做什么：P

编辑：线程函数和中位数的原型包含在头文件median.h中。

Answer 1

更换

std::thread first(thread_function, bgrPixel, input, 0); 

通过

std::thread first(thread_function, std::ref(bgrPixel), std::ref(input), 0); 

活生生的例子：http://coliru.stacked-crooked.com/a/630775aafc3d4642