How can I use std::map in C++11 with multithreading?

How can I use std::map in C++11 with multithreading?

You can use std::map in C++11 with multithreading, but you need to ensure thread safety. One way to do this is by using mutexes to protect access to the map.

Can you show me a code example of that?

Sure! Here's a simple example:

#include <iostream>
#include <map>
#include <thread>
#include <mutex>

std::map<int, int> myMap;
std::mutex mapMutex;

void threadFunction(int id) {
    std::lock_guard<std::mutex> lock(mapMutex);
    myMap[id] = id * 10;
}

int main() {
    std::thread t1(threadFunction, 1);
    std::thread t2(threadFunction, 2);
    t1.join();
    t2.join();
    for (const auto& pair : myMap) {
        std::cout << pair.first << " : " << pair.second << '\n';
    }
    return 0;
}

This code uses a mutex to ensure that only one thread can modify the map at a time.

What happens if I don't use a mutex?

If you don't use a mutex, you may encounter data races, which can lead to undefined behavior. This means that your program might crash or produce incorrect results.

Are there any alternatives to std::map for multithreading?

Yes, you could consider using concurrent data structures like concurrent_hash_map from Intel's Threading Building Blocks or other libraries designed for thread safety.