What are the basic concurrency concepts?

Here are the basic concurrency concepts that are essential to understanding how concurrency works in programming:

1. Threads

A thread is the smallest unit of execution within a program. Multiple threads can run concurrently within a process, sharing the same memory but performing different tasks. Threads allow multitasking within a single program.

2. Processes

A process is an instance of a running program, which can contain multiple threads. Each process has its own memory space. In contrast to threads, processes do not share memory, which makes inter-process communication more complex than communication between threads.

3. Synchronization

Synchronization ensures that multiple threads or processes do not interfere with each other when accessing shared resources. Common synchronization mechanisms include:

• Locks/Mutexes: Ensure that only one thread can access a resource at a time.
• Semaphores: Limit the number of threads that can access a resource concurrently.
• Monitors/Condition Variables: Used to coordinate access between threads that share resources.

4. Race Condition

A race condition occurs when the outcome of a program depends on the relative timing of events in different threads or processes. This typically happens when multiple threads access shared resources without proper synchronization, leading to unpredictable behavior.

5. Deadlock

A deadlock occurs when two or more threads or processes are blocked forever, each waiting for the other to release a resource. It typically happens when there are circular dependencies between resources that the threads need to acquire.

6. Parallelism

Parallelism refers to executing multiple tasks at the same time, typically on multiple CPU cores. It's a subset of concurrency where tasks are actually run simultaneously, taking advantage of multi-core processors.

7. Asynchronous Programming

Asynchronous programming allows a program to initiate an operation and continue with other tasks without waiting for that operation to complete. This is useful for handling input/output operations or network requests that can take time to complete without blocking the entire program.

8. Context Switching

Context switching occurs when the CPU switches between different threads or processes. The state of the currently running thread is saved, and the state of the new thread is loaded. While context switching allows multiple tasks to run seemingly concurrently on a single core, it introduces some overhead.

9. Locks and Mutexes

A lock or mutex ensures that only one thread or process can access a shared resource at a time. When a thread locks a resource, other threads that need the same resource must wait until the lock is released.

10. Atomicity

An atomic operation is one that is completed in a single step without the possibility of interruption. Atomic operations are critical in concurrency to ensure that complex updates to shared data do not lead to inconsistent or incorrect states.

11. Livelock

A livelock is similar to deadlock, but in this case, the threads or processes involved continuously change their state in response to each other without making progress. The system appears active, but no useful work is done.

Conclusion

Understanding these fundamental concurrency concepts is crucial for developing programs that efficiently use resources, avoid conflicts, and run multiple tasks smoothly. Properly handling synchronization, managing threads, and avoiding common pitfalls like race conditions and deadlocks are essential for writing concurrent programs effectively.