Ractor for true parallelism in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Ractor in Ruby?

A Ractor is a Ruby feature that allows true parallel execution by running code in separate, isolated threads with their own memory.

intermediate

How do Ractors communicate with each other?

Ractors communicate by sending messages through channels using methods like send and take, ensuring thread safety without shared memory.

intermediate

Why can't Ractors share mutable objects directly?

Because Ractors have isolated memory to avoid race conditions, mutable objects cannot be shared directly; they must be copied or sent as immutable data.

beginner

Show a simple example of creating a Ractor that returns a value.

r = Ractor.new { 5 * 5 } result = r.take puts result # Outputs 25

intermediate

What is the benefit of using Ractors over traditional threads in Ruby?

Ractors provide true parallelism by running on multiple CPU cores safely, avoiding the Global Interpreter Lock (GIL) limitations of traditional Ruby threads.

What does a Ractor in Ruby provide?

A Shared memory multithreading

B Single-threaded execution

C True parallelism with isolated memory

D Synchronous blocking calls only

Ractors run code in parallel with isolated memory to avoid conflicts.

How do Ractors exchange data safely?

A By sending messages through channels

B By accessing the same object directly

C By sharing global variables

D By using locks and mutexes

Ractors use message passing to communicate safely without shared memory.

Which Ruby version introduced Ractors?

A Ruby 3.0

B Ruby 2.7

C Ruby 3.1

D Ruby 3.2

Ractors were introduced in Ruby 3.0 to enable parallelism.

What happens if you try to share a mutable object between Ractors?

A It works normally

B Ruby raises an error or copies the object

C The object becomes frozen automatically

D The program crashes

Mutable objects cannot be shared directly; Ruby copies or raises an error to maintain safety.

Which method retrieves a value sent from a Ractor?

A get

B send

C receive

D take

The take method receives a message from a Ractor.

Explain how Ractors achieve true parallelism in Ruby and why this is important.

Think about how Ractors run code separately and communicate.

Describe the steps to create a Ractor that calculates a value and returns it to the main program.

Focus on creation, execution, and getting the result.