class Concurrent::CyclicBarrier

A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point. @example

barrier = Concurrent::CyclicBarrier.new(3)
jobs    = Array.new(3) { |i| -> { sleep i; p done: i } }
process = -> (i) do
  # waiting to start at the same time
  barrier.wait
  # execute job
  jobs[i].call
  # wait for others to finish
  barrier.wait
end
threads = 2.times.map do |i|
  Thread.new(i, &process)
end

# use main as well
process.call 2

# here we can be sure that all jobs are processed

Constants

Generation

@!visibility private

Public Class Methods

new(parties, &block) click to toggle source

Create a new ‘CyclicBarrier` that waits for `parties` threads

@param [Fixnum] parties the number of parties @yield an optional block that will be executed that will be executed after

the last thread arrives and before the others are released

@raise [ArgumentError] if ‘parties` is not an integer or is less than zero

Calls superclass method
# File lib/concurrent-ruby/concurrent/atomic/cyclic_barrier.rb, line 40
def initialize(parties, &block)
  Utility::NativeInteger.ensure_integer_and_bounds parties
  Utility::NativeInteger.ensure_positive_and_no_zero parties

  super(&nil)
  synchronize { ns_initialize parties, &block }
end

Public Instance Methods

broken?() click to toggle source

A barrier can be broken when:

  • a thread called the ‘reset` method while at least one other thread was waiting

  • at least one thread timed out on ‘wait` method

A broken barrier can be restored using ‘reset` it’s safer to create a new one @return [Boolean] true if the barrier is broken otherwise false

# File lib/concurrent-ruby/concurrent/atomic/cyclic_barrier.rb, line 105
def broken?
  synchronize { @generation.status != :waiting }
end
number_waiting() click to toggle source

@return [Fixnum] the number of threads currently waiting on the barrier

# File lib/concurrent-ruby/concurrent/atomic/cyclic_barrier.rb, line 54
def number_waiting
  synchronize { @number_waiting }
end
parties() click to toggle source

@return [Fixnum] the number of threads needed to pass the barrier

# File lib/concurrent-ruby/concurrent/atomic/cyclic_barrier.rb, line 49
def parties
  synchronize { @parties }
end
reset() click to toggle source

resets the barrier to its initial state If there is at least one waiting thread, it will be woken up, the ‘wait` method will return false and the barrier will be broken If the barrier is broken, this method restores it to the original state

@return [nil]

# File lib/concurrent-ruby/concurrent/atomic/cyclic_barrier.rb, line 95
def reset
  synchronize { ns_generation_done @generation, :reset }
end
wait(timeout = nil) click to toggle source

Blocks on the barrier until the number of waiting threads is equal to ‘parties` or until `timeout` is reached or `reset` is called If a block has been passed to the constructor, it will be executed once by

the last arrived thread before releasing the others

@param [Fixnum] timeout the number of seconds to wait for the counter or

`nil` to block indefinitely

@return [Boolean] ‘true` if the `count` reaches zero else false on

`timeout` or on `reset` or if the barrier is broken
# File lib/concurrent-ruby/concurrent/atomic/cyclic_barrier.rb, line 66
def wait(timeout = nil)
  synchronize do

    return false unless @generation.status == :waiting

    @number_waiting += 1

    if @number_waiting == @parties
      @action.call if @action
      ns_generation_done @generation, :fulfilled
      true
    else
      generation = @generation
      if ns_wait_until(timeout) { generation.status != :waiting }
        generation.status == :fulfilled
      else
        ns_generation_done generation, :broken, false
        false
      end
    end
  end
end

Protected Instance Methods

ns_generation_done(generation, status, continue = true) click to toggle source
# File lib/concurrent-ruby/concurrent/atomic/cyclic_barrier.rb, line 111
def ns_generation_done(generation, status, continue = true)
  generation.status = status
  ns_next_generation if continue
  ns_broadcast
end
ns_initialize(parties, &block) click to toggle source
# File lib/concurrent-ruby/concurrent/atomic/cyclic_barrier.rb, line 122
def ns_initialize(parties, &block)
  @parties = parties
  @action  = block
  ns_next_generation
end
ns_next_generation() click to toggle source
# File lib/concurrent-ruby/concurrent/atomic/cyclic_barrier.rb, line 117
def ns_next_generation
  @generation     = Generation.new(:waiting)
  @number_waiting = 0
end