Basic usage and principle of fork/join framework

ForkJoin Thread pool framework review

ForkJoin A framework is actually a thread pool ExecutorService The implementation of the , Steal... Through work (work-stealing) Algorithm , Get unfinished tasks from other threads to execute .

Can make full use of the machine's multiprocessor advantages , Use idle threads to quickly complete a large task that can be divided into small tasks in parallel , Similar to divide and conquer algorithm .

ForkJoin The goal of , Is to use all available processing power to improve program response and performance . This article will introduce ForkJoin frame , Source analysis .

ForkJoinPool Core class implementation

ForkJoin The core of the framework is ForkJoinPool class , be based on AbstractExecutorService Expand .

ForkJoinPool A queue array is maintained in WorkQueue[], Every WorkQueue Maintain a ForkJoinTask Array and current worker thread .

ForkJoinPool Work theft is realized (work-stealing) Algorithm and execute ForkJoinTask.

ForkJoinPool, All threads and WorkQueue share , For work theft 、 Task status and work status are synchronized .

Introduction to core attributes

ADD_WORKER: 100000000000000000000000000000000000000000000000 -> 1000 0000 0000 0000, To cooperate with ctl Use... When controlling the number of threads

ctl： control ForkJoinPool Number of threads created ,(ctl & ADD_WORKER) != 0L Create thread when , That is to say ctl Of the 16 Not for 0 when , You can continue to create threads

defaultForkJoinWorkerThreadFactory: Default thread factory