Fiber for cooperative concurrency in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new Fiber that prints a message.

Ruby

fiber = Fiber.new do
  puts [1]
end
fiber.resume

Drag options to blanks, or click blank then click option'

A"Hello from Fiber!"

BFiber.yield

Cresume

Dputs

Attempts:

3 left

💡 Hint

Common Mistakes

Using Fiber.yield instead of a string to print.

Forgetting to put the message inside quotes.

Trying to call resume inside the Fiber block.

The Fiber block should print the string "Hello from Fiber!" using puts.

2fill in blank

medium

Complete the code to yield control back from the Fiber.

Ruby

fiber = Fiber.new do
  puts "Step 1"
  [1]
  puts "Step 2"
end
fiber.resume
fiber.resume

Drag options to blanks, or click blank then click option'

Ayield

BFiber.resume

CFiber.yield

Dresume

Attempts:

3 left

💡 Hint

Common Mistakes

Using yield instead of Fiber.yield inside the Fiber block.

Calling Fiber.resume inside the Fiber block.

Using resume without Fiber prefix.

Fiber.yield pauses the Fiber and returns control to the caller.

3fill in blank

hard

Fix the error in the code to resume the Fiber correctly.

Ruby

fiber = Fiber.new do
  puts "Inside Fiber"
end
[1]

Drag options to blanks, or click blank then click option'

Afiber.start

BFiber.resume

Cfiber.run

Dfiber.resume

Attempts:

3 left

💡 Hint

Common Mistakes

Using fiber.start which does not exist.

Calling Fiber.resume as a class method.

Using fiber.run which is not a Fiber method.

To start or resume a Fiber, call fiber.resume.

4fill in blank

hard

Fill both blanks to create a Fiber that yields a value and resumes with a parameter.

Ruby

fiber = Fiber.new do
  value = Fiber.yield [1]
  puts "Received: #{value}"
end
fiber.resume
fiber.resume([2])

Drag options to blanks, or click blank then click option'

A"yielded value"

B"hello"

C"world"

D42

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a number instead of a string to resume.

Not yielding any value from the Fiber.

Using Fiber.resume instead of fiber.resume.

The Fiber yields the string "yielded value" and resumes receiving "hello".

5fill in blank

hard

Fill all three blanks to create a Fiber that counts and yields each number, then resumes with a message.

Ruby

fiber = Fiber.new do
  (1..3).each do |i|
    message = Fiber.yield [1]
    puts "Count: #{i}, Message: #[2]"
  end
end
fiber.resume
fiber.resume([3])
fiber.resume("Hi")
fiber.resume("Bye")

Drag options to blanks, or click blank then click option'

Ai

Bmessage

C"Hello"

D"Start"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of the variable i to yield.

Printing i instead of the received message.

Passing wrong values to resume.

The Fiber yields the current count i, prints the received message, and resumes with "Start" first.

Practice

1. What is the main purpose of using Fiber in Ruby?

easy

A. To pause and resume tasks manually for cooperative multitasking

B. To create multiple threads that run in parallel automatically

C. To speed up code by running it on multiple CPU cores

D. To handle database connections asynchronously

Solution

1. Step 1: Understand Fiber's role

   Fibers allow manual pausing and resuming of code execution, enabling cooperative multitasking.

2. Step 2: Differentiate from threads

   Unlike threads, Fibers do not run in parallel automatically; they require explicit control.

3. Final Answer:

   To pause and resume tasks manually for cooperative multitasking -> Option A

4. Quick Check:

   Fiber = manual pause/resume [OK]

Hint: Fibers pause and resume tasks manually, not parallel threads [OK]

Common Mistakes:

• Confusing Fibers with threads or parallelism
• Thinking Fibers run automatically in background
• Assuming Fibers speed up CPU usage

2. Which of the following is the correct way to create a Fiber in Ruby?

easy

A. fiber = Fiber.start { puts 'Hello' }

B. fiber = Fiber.new { puts 'Hello' }

C. fiber = Fiber.create { puts 'Hello' }

D. fiber = Fiber.run { puts 'Hello' }

Solution

1. Step 1: Recall Fiber creation syntax

   Ruby uses Fiber.new with a block to create a new Fiber.

2. Step 2: Check other options

   Methods like create, start, or run do not exist for Fiber creation.

3. Final Answer:

   fiber = Fiber.new { puts 'Hello' } -> Option B

4. Quick Check:

   Fiber creation = Fiber.new [OK]

Hint: Use Fiber.new with a block to create a Fiber [OK]

Common Mistakes:

• Using non-existent Fiber methods like create or start
• Forgetting to pass a block to Fiber.new
• Confusing Fiber with Thread syntax

3. What will be the output of the following Ruby code?

fiber = Fiber.new do
  puts 'Step 1'
  Fiber.yield
  puts 'Step 2'
end

fiber.resume
puts 'Between'
fiber.resume

medium

A. Step 2
Between
Step 1

B. Step 1
Step 2
Between

C. Between
Step 1
Step 2

D. Step 1
Between
Step 2

Solution

1. Step 1: Trace first resume call

   Calling fiber.resume runs until Fiber.yield, printing 'Step 1'.

2. Step 2: Trace code after first resume

   After yield, control returns to main, printing 'Between'.

3. Step 3: Trace second resume call

   Second fiber.resume resumes after yield, printing 'Step 2'.

4. Final Answer:

   Step 1 Between Step 2 -> Option D

5. Quick Check:

   Fiber.yield pauses, resume continues [OK]

Hint: Fiber.yield pauses; resume continues after yield [OK]

Common Mistakes:

• Assuming all code runs at first resume
• Confusing order of prints around yield
• Thinking yield stops Fiber permanently

4. Identify the error in this Fiber usage:

fiber = Fiber.new do
  puts 'Start'
  Fiber.yield
  puts 'End'
end

fiber.yield
fiber.resume

medium

A. Calling Fiber.yield outside a Fiber block causes an error

B. Fiber.resume must be called before Fiber.yield

C. Fiber.new requires a parameter for yield count

D. Fiber cannot print inside its block

Solution

1. Step 1: Check where Fiber.yield is called

   The code calls fiber.yield outside the Fiber block, which is invalid.

2. Step 2: Understand Fiber.yield usage

   Fiber.yield is a class method to pause current Fiber, not an instance method on Fiber objects.

3. Final Answer:

   Calling Fiber.yield outside a Fiber block causes an error -> Option A

4. Quick Check:

   Fiber.yield only inside Fiber block [OK]

Hint: Fiber.yield is called inside Fiber block only [OK]

Common Mistakes:

• Calling fiber.yield instead of Fiber.yield
• Expecting Fiber.resume before yield call
• Thinking Fiber.new needs parameters for yield

5. Given two Fibers that alternate printing numbers, what is the output of this code?

fiber1 = Fiber.new do
  3.times do |i|
    puts "Fiber1: #{i}"
    Fiber.yield
  end
end

fiber2 = Fiber.new do
  3.times do |i|
    puts "Fiber2: #{i}"
    Fiber.yield
  end
end

while fiber1.alive? || fiber2.alive?
  fiber1.resume if fiber1.alive?
  fiber2.resume if fiber2.alive?
end

hard

A. Fiber2: 0
Fiber1: 0
Fiber2: 1
Fiber1: 1
Fiber2: 2
Fiber1: 2

B. Fiber1: 0
Fiber1: 1
Fiber1: 2
Fiber2: 0
Fiber2: 1
Fiber2: 2

C. Fiber1: 0
Fiber2: 0
Fiber1: 1
Fiber2: 1
Fiber1: 2
Fiber2: 2

D. Fiber1: 0
Fiber2: 0
Fiber2: 1
Fiber1: 1
Fiber1: 2
Fiber2: 2

Solution

1. Step 1: Understand Fiber alternation

   Each Fiber prints a number then yields, pausing itself.

2. Step 2: Trace the while loop

   The loop resumes fiber1 then fiber2 alternately while they are alive.

3. Step 3: Follow output order

   Output alternates: Fiber1:0, Fiber2:0, Fiber1:1, Fiber2:1, Fiber1:2, Fiber2:2.

4. Final Answer:

   Fiber1: 0 Fiber2: 0 Fiber1: 1 Fiber2: 1 Fiber1: 2 Fiber2: 2 -> Option C

5. Quick Check:

   Fibers alternate resume and yield [OK]

Hint: Fibers alternate resume and yield to interleave output [OK]

Common Mistakes:

• Assuming one Fiber runs completely before the other
• Mixing order of Fiber resumes
• Forgetting Fiber.yield pauses execution