# Introduce Types of Concurrency in 3 Minutes


<!--more-->

# Concurrency
## Parallelism
* One task in multiprocessor, map the task to the multiple nodes and reduce the results into one node after the computation
* Usually is used on the complex computation or large simulation
## Asynchronous
### Coroutine
* Why we need coroutine?
	* If we handle the IO bound through the multiple blocking system call directly, we would increase the frequency of the context switch
	* A lightweight mechanism to switch between the IO operation in single thread at programmer perspective
	* Avoid the overhead of the context switch caused by OS
* What does coroutine do?
	* Hang on the IO bound task with non-blocking system call
	* While we waiting on the gathered hang on tasks,  we check the status in event loop continuously
### Publisher Subscriber
* Use event broker to decouple the publisher and subscriber
### Producer Consumer
* The communication between producer and consumer is not restrict in message queue, it also could be just a in-memory buffer to exchange the event message for increasing the performance