Concurrency vs Parallelism

Concurrency and parallelism are two concepts that are often used in the context of computer programming and software development.

Concurrency

Concurrency refers to the ability of a system to perform multiple tasks or processes simultaneously, without necessarily executing them at the same time.

In other words, a concurrent system may appear to be executing multiple tasks at the same time, but in reality, it is switching rapidly between different tasks to give the impression of parallelism.

Example

In a multi-threaded program, multiple threads may be running concurrently on the same processor, but only one thread can execute at a time.

The operating system scheduler switches rapidly between different threads, giving the impression that they are all executing in parallel.

Parallelism

Parallelism, on the other hand, refers to the ability of a system to execute multiple tasks or processes at the same time, using multiple processors or cores.

In a parallel system, each processor or core can execute a different task simultaneously, allowing for true parallelism.

Example

In a parallel computing system, a single computation can be broken down into smaller sub-tasks, which can be executed simultaneously on different processors or cores, allowing the computation to be completed much faster than it would be on a single processor.