Thread creation and execution in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a thread in Ruby?

A thread is a lightweight unit of execution within a Ruby program that allows multiple tasks to run at the same time.

beginner

How do you create a new thread in Ruby?

Use Thread.new { ... } to create and start a new thread that runs the code inside the block.

beginner

What does thread.join do in Ruby?

It makes the main program wait until the thread finishes its work before continuing.

intermediate

Can Ruby threads run truly in parallel?

MRI Ruby threads are native threads and run concurrently but not truly in parallel because of the Global Interpreter Lock (GIL).

intermediate

What happens if you don't join a thread in Ruby?

The main program may finish before the thread completes, causing the thread to be killed prematurely.

How do you start a new thread in Ruby?

A start_thread()

B Thread.start()

C Thread.new { code }

D new Thread()

In Ruby, Thread.new { ... } creates and starts a new thread running the code inside the block.

What method waits for a thread to finish before continuing?

A wait()

B join()

C sleep()

D stop()

join() pauses the main thread until the called thread completes.

Which Ruby implementation has a Global Interpreter Lock (GIL) affecting threads?

A MRI Ruby

B Rubinius

C JRuby

D TruffleRuby

MRI Ruby uses a GIL, so threads run concurrently but not in true parallel.

What happens if the main program ends before a thread finishes?

A Thread is killed

B Thread is paused

C Thread continues running in background

D Thread restarts

If the main program ends, any running threads are killed immediately.

Which of these is a correct way to create and run a thread that prints 'Hello'?

A Thread.run { print 'Hello' }

B Thread.start { puts 'Hello' }

C Thread.create { echo 'Hello' }

D Thread.new { puts 'Hello' }

Thread.new { puts 'Hello' } creates and runs a thread that prints 'Hello'.

Explain how to create and execute a thread in Ruby and why you might want to use join.

Think about starting a task in the background and waiting for it to finish.

Describe the effect of the Global Interpreter Lock (GIL) on Ruby threads and how it impacts parallel execution.

Consider how threads share the CPU in MRI Ruby.