Types of Concurrency Models

Concurrency vs Parallelism

Concurrency is about dealing with lots of things at once
Parallelism is about doing lots of things at once

Levels of Parallelism

Bit-level: i.e. 16, 32, 64-bit architectures.
Instruction-level
Data parallelism
Task-level

A Big Question

What is the bottleneck between Parallel-Multi-Core-Fast & need to your code to go Non-Blocking?

Answer: Shared Mutable State

Why so many concurrency models

Concurrency Models help eliminate complexities which rises when one have to choose to move the code execution in concurrent mode. They try to imply mechanisms to somehow manage/eliminate Shared Mutable State.

One can achieve concurrency without a worry if they can

Eliminate Shared Mutable State
OR
Make the data share transactional. (ACID Properties)

Features of Concurrency Models

All the models which exists till date sort of tries to eliminate one of (shared/mutable/state) or make things transactional.

Types of Concurrency Models

Threads & Locks
Atomics Condition Variables & Timeouts (beyond locks)
Functional Programming
Actors
Communicating Sequential Process
Software Transaction Memory
Data Parallelism
Lambda Approach
Event-based System