thread_pool.rb

# pool_size: number of threads
# jobs: A queue (See: https://rubyapi.org/3.0/o/queue)
def thread_pool(pool_size: 4, jobs:, &block)
  threads = []
  results = []
  mutex = Mutex.new

  pool_size.times do
    threads << Thread.new do
      while !jobs.empty? do
        job = jobs.pop(true)
        result = block.call(job)
        mutex.synchronize { results << result }
      end
    end
  end
  threads.map(&:join)
  results
end