Concurrency is a fundamental concept in programming that allows multiple tasks to be executed simultaneously. This tutorial will guide you through the basics of concurrency and how it can be implemented in various programming languages.

Concurrency refers to the ability of a computer to execute multiple tasks simultaneously. This is different from parallelism, which refers to the actual execution of multiple tasks at the same time on multiple processors.

Types of Concurrency

There are several types of concurrency models:

  • Thread-based: Using threads to execute tasks concurrently.
  • Process-based: Using processes to execute tasks concurrently.
  • Event-driven: Using events to trigger the execution of tasks.

Thread-based Concurrency

Thread-based concurrency is the most common model in modern programming. It allows multiple threads to run concurrently within the same process.

Creating Threads

To create a thread, you typically use a language-specific API. For example, in Python, you can use the threading module:

import threading

def print_numbers():
    for i in range(1, 6):
        print(i)

t = threading.Thread(target=print_numbers)
t.start()
t.join()

Synchronization

When multiple threads access shared resources, synchronization mechanisms are used to prevent race conditions and ensure data consistency.

Locks

Locks are a common synchronization mechanism. They ensure that only one thread can access a shared resource at a time.

import threading

lock = threading.Lock()

def print_numbers():
    for i in range(1, 6):
        with lock:
            print(i)

t = threading.Thread(target=print_numbers)
t.start()
t.join()

Process-based Concurrency

Process-based concurrency is another common model, where each process runs in its own address space.

Creating Processes

To create a process, you typically use a language-specific API. For example, in Python, you can use the multiprocessing module:

from multiprocessing import Process

def print_numbers():
    for i in range(1, 6):
        print(i)

p = Process(target=print_numbers)
p.start()
p.join()

Event-driven Concurrency

Event-driven concurrency is often used in web applications and GUIs, where tasks are triggered by events.

Callbacks

Callbacks are functions that are executed when an event occurs. They are commonly used in event-driven programming.

def on_click():
    print("Button clicked!")

# Bind the callback to the event
button.on_click(on_click)

Conclusion

Concurrency is a powerful concept that allows you to write more efficient and responsive applications. By understanding the different concurrency models and their implementation details, you can make informed decisions when designing your applications.

For more information on concurrency, check out our Concurrency Deep Dive.

Concurrency Concept