Class: Concurrent::CountDownLatch

Inherits:

CountDownLatchImplementation

Object
Concurrent::CountDownLatch

show all

Defined in:: lib/concurrent/atomic/count_down_latch.rb

Overview

A synchronization object that allows one thread to wait on multiple other threads. The thread that will wait creates a CountDownLatch and sets the initial value (normally equal to the number of other threads). The initiating thread passes the latch to the other threads then waits for the other threads by calling the #wait method. Each of the other threads calls #count_down when done with its work. When the latch counter reaches zero the waiting thread is unblocked and continues with its work. A CountDownLatch can be used only once. Its value cannot be reset.

Examples:

Waiter and Decrementer

latch = Concurrent::CountDownLatch.new(3)

waiter = Thread.new do
  latch.wait()
  puts ("Waiter released")
end

decrementer = Thread.new do
  sleep(1)
  latch.count_down
  puts latch.count

  sleep(1)
  latch.count_down
  puts latch.count

  sleep(1)
  latch.count_down
  puts latch.count
end

[waiter, decrementer].each(&:join)

Instance Method Summary collapse

#count ⇒ Fixnum
The current value of the counter.
#count_down ⇒ undocumented
Signal the latch to decrement the counter.
#initialize(count = 1) ⇒ undocumented constructor
Create a new CountDownLatch with the initial count.
#wait(timeout = nil) ⇒ Boolean
Block on the latch until the counter reaches zero or until timeout is reached.

Constructor Details

#initialize(count = 1) ⇒ `undocumented`

Create a new CountDownLatch with the initial count.

Parameters:

count (new) (defaults to: 1) —
the initial count

Raises:

(ArgumentError) —
if count is not an integer or is less than zero



98
99

# File 'lib/concurrent/atomic/count_down_latch.rb', line 98

class CountDownLatch < CountDownLatchImplementation
end

Instance Method Details

#count ⇒ `Fixnum`

The current value of the counter.

Returns:

(Fixnum) —
the current value of the counter



98
99

# File 'lib/concurrent/atomic/count_down_latch.rb', line 98

class CountDownLatch < CountDownLatchImplementation
end

#count_down ⇒ `undocumented`

Signal the latch to decrement the counter. Will signal all blocked threads when the count reaches zero.



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99

# File 'lib/concurrent/atomic/count_down_latch.rb', line 98

class CountDownLatch < CountDownLatchImplementation
end

#wait(timeout = nil) ⇒ `Boolean`

Block on the latch until the counter reaches zero or until timeout is reached.