[英]printing duplications when using threads c++
I'm trying to write a basic code for my bigger program.我正在尝试为我的更大程序编写基本代码。 The original code suppose to write on a txt file some results of my calculations but here I changed it to write the numer 1 (to simplify the code).
原始代码假设在 txt 文件上写入我的一些计算结果,但在这里我将其更改为写入数字 1(以简化代码)。 The problem is that I dont get the number of ones I suppose to get... instede of 1000 prints of 1 I get a bigger and random number of 1 each running...
问题是我没有得到我想得到的数量……而不是 1000 次打印,我每次运行都会得到一个更大的随机数 1……
What is the problem with my code?我的代码有什么问题?
(I'm using windows 10, codeblock workspace, I'm writing the code in c++) (我使用的是 Windows 10,代码块工作区,我正在用 C++ 编写代码)
The code:编码:
#include <iostream>
#include <thread>
#include <vector>
#include <fstream>
using namespace std;
ofstream myfile;
void doTask()
{
myfile << "1\n";
}
void f()
{
vector<thread> threads;
for(int i = 0; i < 10; ++i)
{
threads.push_back(thread(doTask));
}
for(int j=0; j<10; j++) threads[j].join();
threads.erase(threads.begin(), threads.end());
}
int main()
{
myfile.open("a.txt");
for(int i=0; i<100; i++) f();
myfile.close();
return 0;
}
Thank you all!谢谢你们!
Make ofstream thread safe.使 ofstream 线程安全。 Following will do.
以下会做。
#include <iostream>
#include <thread>
#include <vector>
#include <fstream>
#include <mutex>
using namespace std;
ofstream myfile;
std::mutex myMutex;
void doTask()
{
myMutex.lock();
myfile << "1\n";
myMutex.unlock();
}
void f()
{
vector<thread> threads;
for(int i = 0; i < 10; ++i)
{
threads.push_back(thread(doTask));
}
for(int j=0; j<10; j++) threads[j].join();
threads.erase(threads.begin(), threads.end());
}
int main()
{
myfile.open("a.txt");
for(int i=0; i<100; i++) f();
myfile.close();
return 0;
}
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