In order to decide what thread to start or resume a coroutine on, a coroutine dispatcher is used. All coroutine dispatchers must implement the CoroutineDispatcher interface:

• DefaultDispatcher: Currently it is the same as CommonPool. In the future, this may change.
• CommonPool: Executes and resumes the coroutines in a pool of shared background threads. Its default size makes it optimal for use in CPU-bound operations.
• Unconfined: Starts the coroutine in the current thread (the thread from which the coroutine was invoked), but will resume the coroutine in any thread. No thread policy is used by this dispatcher.

Along with these dispatchers, there are a couple of builders that can be used to define pools or threads as needed:

• newSingleThreadContext() to build a dispatcher with a single thread; the coroutines executed here will be started and resumed in the same thread, always.
• newFixedThreadPoolContext() creates a dispatcher with a pool of threads of the given size. The runtime will decide which thread to use when starting and resuming the coroutines executed in the dispatcher.