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Multithreading in C++
Multithreading is the concurrent execution of multiple threads within a single process or program. It improves the performance and efficiency of an application by allowing multiple tasks to be executed in parallel.
In C++, multithreading support is available through the thread library introduced in the C++11 standard.
Basic Thread Creation
To create a new thread, include the <thread> header file and create an instance of std::thread that takes a function as an argument. The function will be executed in a new thread.
#include <iostream>
#include <thread>
void my_function() {
std::cout << "This function is executing in a separate thread" << std::endl;
}
int main() {
std::thread t(my_function);
t.join(); // waits for the thread to complete
return 0;
}
Thread with Arguments
You can pass arguments to the thread function by providing them as additional arguments to the std::thread constructor.
#include <iostream>
#include <thread>
void print_sum(int a, int b) {
std::cout << "The sum is: " << a + b << std::endl;
}
int main() {
std::thread t(print_sum, 3, 5);
t.join();
return 0;
}
Mutex and Locks
When multiple threads access shared resources, there is a possibility of a data race. To avoid this, use mutex and locks to synchronize shared resource access.
#include <iostream>
#include <mutex>
#include <thread>
std::mutex mtx;
void print_block(int n, char c) {
{
std::unique_lock<std::mutex> locker(mtx);
for (int i = 0; i < n; ++i) {
std::cout << c;
}
std::cout << std::endl;
}
}
int main() {
std::thread t1(print_block, 50, '*');
std::thread t2(print_block, 50, '$');
t1.join();
t2.join();
return 0;
}
This short introduction should help you get started with basic multithreading techniques in C++. There is a lot more to learn, such as thread pools, condition variables, and atomic operations for advanced synchronization and performance tuning.