Actor-Model Computation

1. Overview

Definition: Actor-model computation is an abstraction used in computer science to model computation as a collection of "actors."
Actors: The fundamental units of computation in this model that encapsulate state and behavior, interact with each other through asynchronous message passing.
Concurrency: Supports concurrent computation by allowing actors to operate independently and in a non-blocking manner.
Location Transparency: Actors can communicate regardless of their physical location in a system, enabling distributed computing.
Fault Tolerance: The model encourages building systems that can gracefully handle failures by isolating actors.

Message Passing: Actors communicate by sending messages, ensuring that interactions are loosely coupled.
State Management: Each actor maintains its own state and is responsible for managing it, thus simplifying reasoning about state changes.
Supervisor Hierarchy: An organizational structure where actors can supervise other actors, enabling a robust fault recovery mechanism.

The actor model contrasts with shared-state concurrency models, where threads share memory and require synchronization, leading to complexities like deadlocks and race conditions.
Applications: Widely used in systems requiring high concurrency, such as telecommunications (e.g., Erlang), distributed systems, and real-time applications.
It has influenced various programming languages and frameworks, promoting a paradigm centered on concurrency and parallelism, most notably in languages like Scala and Akka.