thread_sum.rb

#!/usr/bin/env ruby

threads = 100.times.map do |n|
  Thread.new n do |m|
    base = 1 + (m * 100)
    100.times.map do |i|
      base + i
    end
  end
end

result = threads.reduce(0) do |sum, thread|
  sum + thread.join.value.reduce(:+)
end

puts "The multi-threaded result is: #{result}"