sample.rb

  def self.set_threads(num_threads)
    # puts "Creating thread pool with #{num_threads} threads"
    @thread_pool = Concurrent::FixedThreadPool.new(num_threads)
  end
...
    for index in 0..(samples.size - samples_to_mix) do
      futures.push Concurrent::Future.new(
        # arguments for Future construction
        {
          # @thread_pool must already be set
          :executor => @thread_pool,
          # these args will be passed to the Proc upon execution
          #   failure to properly pass the args will result in the Proc sharing
          #   values between multple Futures
          :args => [index, samples_to_mix, samples[index]]
        }
      ) { |index, samples_to_mix, sample|
          MixtureMaker.mix_and_count_recursive( \
            index + 1, \
            samples_to_mix - 1, \
            sample
          )
        }.execute
    end

    futures.each_with_index { |future, index|

      temp_allele_counts_by_locus, temp_max_alleles_total, temp_different_maxes, temp_dropin_total = future.value
      ...
    }