- Previously, we talked about threads

- What is a mutex?

- Mutual exclusion (venn diagram, where the 2 circles don't meet)

- Why do we need mutex?

- Prevent race conditions + data corruption

- Show how threads can overwrite data

- How does mutex fix it?

- Lock/unlock outside the for-loop

- Why you need to be careful with mutexes?

- Lock/unlock inside the for-loop

- What is a C++ Mutex and How Does it?

- ChatGPT and Gemini

#include <iostream>

#include <mutex>

#include <thread>

using namespace std;

std::mutex counter_mtx;

int counter = 0;

void increment_counter() {

counter_mtx.lock();

for (size_t i = 0; i < 1000000; i++) {

counter++;

}

counter_mtx.unlock();

}

int main() {

// cout << "start count: " << counter << endl;

// std::thread t1(increment_counter);

// std::thread t2(increment_counter);

// t1.join();

// t2.join();

// cout << "end count: " << counter << endl;

cout << "start count: " << counter << endl;

auto start = std::chrono::high_resolution_clock::now();

std::thread t1(increment_counter);

std::thread t2(increment_counter);

t1.join();

t2.join();

auto end = std::chrono::high_resolution_clock::now();

cout << "end count: " << counter << endl;

std::chrono::duration<double, std::milli> elapsed = end - start;

cout << "Function took: " << elapsed.count() << " ms" << endl;

return 0;

}