Compare concurrency and parallelism.

Concurrency and parallelism are two terms often used in computing to describe the execution of tasks.

1. Concurrency: Concurrency is when two or more tasks can start, run, and complete in overlapping time periods. It doesn't necessarily mean they'll be running at the same instant. For example, multitasking on a single-core machine.

2. Parallelism: Parallelism is when tasks literally run at the same time, e.g., on a multicore processor.

Comparison:

• Concurrency is about dealing with lots of things at once. Parallelism is about doing lots of things at once.
• Not all concurrent programming is parallel, though, e.g., multitasking on a single-core machine.
• Parallelism is a subset of concurrency. It is the situation where concurrency is achieved with independent execution processes.
• Concurrency is a property of systems in which several independent tasks are executing at the same time. The tasks may be executing on multiple cores, multiple processors, or even distributed systems.
• Parallelism is a type of concurrent execution where tasks are broken down into smaller subtasks that can be processed simultaneously. This is particularly useful in situations where a task can be divided into independent subtasks.

In summary, while these terms are related, they describe different concepts. Concurrency is a broader term that includes the concept of parallelism as a subset.