[Solved] What will be the output of this Ruby code? require 'thread' mutex = Mutex.new counter = 0 threads = 5.times.map do Thread.new do 10.times do mutex.... What will be the output of this Ruby code? | Ruby

Ruby - Concurrent Programming

What will be the output of this Ruby code?

require 'thread'
mutex = Mutex.new
counter = 0
threads = 5.times.map do
  Thread.new do
    10.times do
      mutex.synchronize { counter += 1 }
    end
  end
end
threads.each(&:join)
puts counter

A10

B0

C5

D50

Step-by-Step Solution

Solution:

Step 1: Analyze thread and loop counts
There are 5 threads, each incrementing counter 10 times, total increments = 5 * 10 = 50.
Step 2: Understand Mutex protection
Mutex ensures increments happen safely without lost updates, so counter will be exactly 50.
Final Answer:
50 -> Option D
Quick Check:
5 threads * 10 increments = 50 [OK]

Quick Trick: Multiply threads by increments with Mutex [OK]

Common Mistakes:

Ignoring Mutex and expecting less than 50
Confusing thread count with increments
Assuming race conditions reduce count

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What will be the output of this Ruby code?

Step 1: Analyze thread and loop counts

Step 2: Understand Mutex protection

Final Answer:

Quick Check:

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