Work stealing is a technique used by modern thread-pools in order to decrease contention on the work queue. A classical threadpool has one queue, and each thread-pool-thread locks the queue, dequeue a task and then unlocks the queue. If the tasks are short and there are many of them, there is a lot of contention … Read more
You need to import operators that are not loaded by default. That’s what EXCEPTION Observable.xxxx is not a function usually means. You can either import all operators by adding complete rxjs to your bootstrap, for example: import ‘rxjs/Rx’ or by importing specific operators, in your case: import ‘rxjs/add/observable/forkJoin’ Another observation/suggestion about your code: try to … Read more
One key difference is that F-J seems to be designed to work on a single Java VM, while M-R is explicitly designed to work on a large cluster of machines. These are very different scenarios. F-J offers facilities to partition a task into several subtasks, in a recursive-looking fashion; more tiers, possibility of ‘inter-fork’ communication … Read more
There’re related questions on stackoverflow: ForkJoinPool stalls during invokeAll/join ForkJoinPool seems to waste a thread I made a runnable stripped down version of what is happening (jvm arguments i used: -Xms256m -Xmx1024m -Xss8m): import java.util.ArrayList; import java.util.List; import java.util.concurrent.ForkJoinPool; import java.util.concurrent.RecursiveAction; import java.util.concurrent.RecursiveTask; import java.util.concurrent.TimeUnit; public class Test1 { private static ForkJoinPool pool = new … Read more
Nothing is truly parallel in node.js since it is single threaded. However, multiple events can be scheduled and run in a sequence you can’t determine beforehand. And some things like database access are actually “parallel” in that the database queries themselves are run in separate threads but are re-integrated into the event stream when completed. … Read more
Fork-join allows you to easily execute divide and conquer jobs, which have to be implemented manually if you want to execute it in ExecutorService. In practice ExecutorService is usually used to process many independent requests (aka transaction) concurrently, and fork-join when you want to accelerate one coherent job.
I found a bug report of a very similar case (JDK-8143380) which was closed as “Not an Issue” by Stuart Marks: This is a class initialization deadlock. The test program’s main thread executes the class static initializer, which sets the initialization in-progress flag for the class; this flag remains set until the static initializer completes. … Read more
I think the basic misunderstanding is, that the Fork/Join examples do NOT show work stealing but only some kind of standard divide and conquer. Work stealing would be like this: Worker B has finished his work. He is a kind one, so he looks around and sees Worker A still working very hard. He strolls … Read more