MRI Multi-threading

fibonacci.rb

# frozen_string_literal: true

def fibonacci(n)
  return n if n <= 1
  fibonacci(n - 1) + fibonacci(n - 2)
end

def calculate(id: 1, n: 40)
  start = Time.now
  puts "Start ##{id}: #{start}"
  puts fibonacci(n)
  finish = Time.now
  puts "Finish ##{id}: #{finish} (#{finish - start} seconds)"
end

puts 'One thread:'
calculate id: 0

puts 'Two threads:'

threads = 2.times.with_object([]) do |i, arr|
  arr << Thread.new { calculate id: i + 1 }
end

threads.each(&:join)

# $ ruby fibonacci.rb 
# One thread:
# Start #0: 2017-05-02 01:05:14 +0300
# 102334155
# Finish #0: 2017-05-02 01:05:24 +0300 (9.72420595 seconds)
# Two threads:
# Start #1: 2017-05-02 01:05:24 +0300
# Start #2: 2017-05-02 01:05:24 +0300
# 102334155
# Finish #1: 2017-05-02 01:05:43 +0300 (18.78237694 seconds)
# 102334155
# Finish #2: 2017-05-02 01:05:43 +0300 (19.151724752 seconds)