class Fiber::ExecutionContext::Concurrent

• Fiber::ExecutionContext::Concurrent
• Reference
• Object

Overview

Concurrent-only execution context.

Fibers running in the same context can only run concurrently and never in parallel to each others. However, they still run in parallel to fibers running in other execution contexts.

Fibers in this context can use simpler and faster synchronization primitives between themselves (for example no atomics or thread safety required), but data shared with other contexts needs to be protected (e.g. Mutex), and communication with fibers in other contexts requires safe primitives, for example Channel.

A blocking fiber blocks the entire context, and thus all the other fibers in the context.

For example: we can start a concurrent context to run consumer fibers, while the default context produces values. Because the consumer fibers will never run in parallel and don't yield between reading result then writing it, we are not required to synchronize accesses to the value:

require "wait_group"

consumers = Fiber::ExecutionContext::Concurrent.new("consumers")
channel = Channel(Int32).new(64)
wg = WaitGroup.new(32)

result = 0

32.times do
  consumers.spawn do
    while value = channel.receive?
      # safe, but only for this example:
      result = result + value
    end
  ensure
    wg.done
  end
end

1024.times { |i| channel.send(i) }
channel.close

# wait for all workers to be done
wg.wait

p result # => 523776

In practice, we still recommended to always protect shared accesses to a variable, for example using Atomic#add to increment result or a Mutex for more complex operations.

Included Modules

• Fiber::ExecutionContext
• Fiber::ExecutionContext::Scheduler

Defined in:

Constructors

• .new(name : String) : self

Instance Method Summary

• #inspect(io : IO) : Nil

  Appends a String representation of this object which includes its class name, its object address and the values of all instance variables.

• #name : String
• #status : String

  Returns the current status of the scheduler.

• #to_s(io : IO) : Nil

  Appends a short String representation of this object which includes its class name and its object address.

Constructor Detail

Instance Method Detail

class Person
  def initialize(@name : String, @age : Int32)
  end
end

Person.new("John", 32).inspect # => #<Person:0x10fd31f20 @name="John", @age=32>

class Person
  def initialize(@name : String, @age : Int32)
  end
end

Person.new("John", 32).to_s # => #<Person:0x10a199f20>