[Solved] What will be the output of this Ruby code? require 'thread' mutex = Mutex.new counter = 0 threads = 3.times.map do Thread.new do 2.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 = 3.times.map do
  Thread.new do
    2.times do
      mutex.synchronize { counter += 1 }
    end
  end
end
threads.each(&:join)
puts counter

A2

B3

C6

D0

Step-by-Step Solution

Solution:

Step 1: Count total increments
There are 3 threads, each increments counter 2 times, total 3*2=6 increments.
Step 2: Understand mutex effect
Mutex ensures increments happen safely without losing counts, so final counter is 6.
Final Answer:
6 -> Option C
Quick Check:
3 threads * 2 increments each = 6 [OK]

Quick Trick: Multiply threads by increments inside synchronize block [OK]

Common Mistakes:

Ignoring mutex and expecting wrong count
Counting only one thread's increments
Confusing thread join effect

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What will be the output of this Ruby code?

Step 1: Count total increments

Step 2: Understand mutex effect

Final Answer:

Quick Check:

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