class Concurrent::RubyThreadPoolExecutor

def ns_initialize(opts)
  @min_length      = opts.fetch(:min_threads, DEFAULT_MIN_POOL_SIZE).to_i
  @max_length      = opts.fetch(:max_threads, DEFAULT_MAX_POOL_SIZE).to_i
  @idletime        = opts.fetch(:idletime, DEFAULT_THREAD_IDLETIMEOUT).to_i
  @max_queue       = opts.fetch(:max_queue, DEFAULT_MAX_QUEUE_SIZE).to_i
  @synchronous     = opts.fetch(:synchronous, DEFAULT_SYNCHRONOUS)
  @fallback_policy = opts.fetch(:fallback_policy, :abort)
  raise ArgumentError.new("`synchronous` cannot be set unless `max_queue` is 0") if @synchronous && @max_queue > 0
  raise ArgumentError.new("#{@fallback_policy} is not a valid fallback policy") unless FALLBACK_POLICIES.include?(@fallback_policy)
  raise ArgumentError.new("`max_threads` cannot be less than #{DEFAULT_MIN_POOL_SIZE}") if @max_length < DEFAULT_MIN_POOL_SIZE
  raise ArgumentError.new("`max_threads` cannot be greater than #{DEFAULT_MAX_POOL_SIZE}") if @max_length > DEFAULT_MAX_POOL_SIZE
  raise ArgumentError.new("`min_threads` cannot be less than #{DEFAULT_MIN_POOL_SIZE}") if @min_length < DEFAULT_MIN_POOL_SIZE
  raise ArgumentError.new("`min_threads` cannot be more than `max_threads`") if min_length > max_length
  @pool                 = [] # all workers
  @ready                = [] # used as a stash (most idle worker is at the start)
  @queue                = [] # used as queue
  # @ready or @queue is empty at all times
  @scheduled_task_count = 0
  @completed_task_count = 0
  @largest_length       = 0
  @workers_counter      = 0
  @ruby_pid             = $$ # detects if Ruby has forked
  @gc_interval  = opts.fetch(:gc_interval, @idletime / 2.0).to_i # undocumented
  @next_gc_time = Concurrent.monotonic_time + @gc_interval
end