| package kotlinx.coroutines.experimental |
| |
| import java.util.concurrent.Executor |
| import java.util.concurrent.Executors |
| import java.util.concurrent.ForkJoinPool |
| import java.util.concurrent.atomic.AtomicInteger |
| import kotlin.coroutines.CoroutineContext |
| |
| /** |
| * Represents common pool of shared threads as coroutine dispatcher for compute-intensive tasks. |
| * It uses [ForkJoinPool] when available, which implements efficient work-stealing algorithm for its queues, so every |
| * coroutine resumption is dispatched as a separate task even when it already executes inside the pool. |
| * When available, it wraps [ForkJoinPool.commonPool] and provides a similar shared pool where not. |
| */ |
| object CommonPool : CoroutineDispatcher() { |
| private val pool: Executor = findPool() |
| |
| private inline fun <T> Try(block: () -> T) = try { block() } catch (e: Throwable) { null } |
| |
| private fun findPool(): Executor { |
| val fjpClass = Try { Class.forName("java.util.concurrent.ForkJoinPool") } |
| ?: return createPlainPool() |
| Try { fjpClass.getMethod("commonPool")?.invoke(null) as? Executor } |
| ?. let { return it } |
| Try { fjpClass.getConstructor(Int::class.java).newInstance(defaultParallelism()) as? Executor } |
| ?. let { return it } |
| return createPlainPool() |
| } |
| |
| private fun createPlainPool(): Executor { |
| val threadId = AtomicInteger() |
| return Executors.newFixedThreadPool(defaultParallelism()) { |
| Thread(it, "CommonPool-worker-${threadId.incrementAndGet()}").apply { isDaemon = true } |
| } |
| } |
| |
| private fun defaultParallelism() = (Runtime.getRuntime().availableProcessors() - 1).coerceAtLeast(1) |
| |
| override fun isDispatchNeeded(context: CoroutineContext): Boolean = true |
| override fun dispatch(context: CoroutineContext, block: Runnable) = pool.execute(block) |
| } |