c++ - 等待线程直到另一个线程结束 C++ linux OS

Question

我的项目中有三个用 C++ 编写的函数，在同一个 .cpp 文件中，我有两个 .h 文件。现在，我有三个相应的线程，第二个线程从第一个线程获取输出，最后一个线程等待第二个线程结束它的操作。注意线程处于“永远循环”中，即 while(1 ){..}

//source.cpp 看起来像这样:

#include <iostream>
#include "source.h"
#include "glob_variables.h"
#include "armadillo"
#include <vector>
using namespace arma;
using namespace std;

void source::first_function(int size)
{
  for(int i=0;i<size;i++)
  {
   container.push_back(i);//container is global variable vector of type int declared in glob_variables.h
  }
}
//~~~~~~~~~~~~~~~~~~~~~~
void source::second_function()
{
   //sleep until the first function fills the the vector to set set its size to matrix.n_rows 
  matrix.set_size(container.size(),33);
   for(int i=0;i<container.size();i++)
   {
    for(int j=0;j<50;j++)
     {
       matrix(i,j)=i+j;//matrix is also a global variable in glob_variables.h
     }
   }
}
//~~~~~~~~~~~~~~~~~~~~~~
void source::third_function()
{
//sleep untill the second function fills the matrix, then print
cout<<matrix;//print out the matrix
}

//源代码.h

#include "glob_variables.h"
#include "armadillo"
#include <vector>
using namespace arma;
using namespace std;
class source
{
public:
 void first_function(int size);
 void second_function();
 void third_function();
};

//glob_variables.h

#include "armadillo"
#include <vector>
using namespace arma;
using namespace std;

extern mat matrix;
extern vector<int> container;

//主程序.cpp

    #include <iostream>
    #include <stdio.h>
    #include <pthread.h>
    #include "source.h"
    #include "glob_variables.h"
    #include "armadillo"
    #include <vector>
    using namespace arma;
    using namespace std;

//thread functions
     void* first_reader(void* id1)
     {
       source mysource;
       while(1)
       {
         mysource.first_function(80);
       }
     }

     void* second_reader(void* id2)
     {
       source mysource;
       while(1)
       {
         mysource.second_function();
       }
     }

     void* third_reader(void* id3)
     {
       source mysource;
       while(1)
       {
        mysource.third_function();
       }
     }

   int main()
   {
    pthread_t first;
    pthread_t second;
    pthread_t third;

    int hndl_first;
    int hndl_second;
    int hndl_third;

    hndl_first = pthread_create(&first, NULL, first_reader, NULL);
    hndl_second= pthread_create(&second, NULL, second_thread, NULL);
    hndl_third;= pthread_create(&third, NULL,third_thread, NULL);

   pthread_exit(NULL);
   return 0; 
   }

我有什么技巧可以做到这一点，或者任何简单的例子。谢谢。

Answer 1

来自documentation

attributes

.n_rows           number of rows; present in Mat, Col, Row, Cube, field and SpMat
.n_cols           number of columns; present in Mat, Col, Row, Cube, field and SpMat
.n_elem           total number of elements; present in Mat, Col, Row, Cube, field and SpMat
.n_slices             number of slices; present in Cube
.n_nonzero            number of non-zero elements; present in SpMat

Member variables which are read-only; to change the size, use .set_size(), .copy_size(), .zeros(), .ones(), or .reset()

所以，照他们说的去做，使用

matrix.set_size(container.size(),50);