I have a simple question on using the fork join thread pool. Here is a short example of what I'm using: executor = "fork-join-executor" # Configuration for the fork join pool fork-join-executor...

I'm new to Java and is trying to learn the concept of high level concurrency. I saw this code at Java Tutorial Oracle. However, when I run the code, the IDE output an image that is entire black. Wh...

I came across a strange situation where using a parallel stream with a lambda in a static initializer takes seemingly forever with no CPU utilization. Here's the code: class Deadlock { static { ...

Is it possible to configure ForkJoinPool to use 1 execution thread? I am executing code that invokes Random inside a ForkJoinPool. Every time it runs, I end up with different runtime behavior, mak...

What does Async mode of ForkJoinPool mean? Javadoc mentions that it makes queues (is it per-thread queue?) FIFO instead of LIFO. What does it mean in practice?

I was reading Java ForkJoin framework. What extra benefits are there by not directly call invoke() on an implementation of ForkJoinTask (e.g. RecursiveTask), but to instantiate ForkJoinPool and cal...

The event-driven programming model of node.js makes it somewhat tricky to coordinate the program flow. Simple sequential execution gets turned into nested callbacks, which is easy enough (though a...

In a ForkJoinPool ForkJoinTask, does the current worker thread participate in work stealing? I have read implications that a fork join pool can work steal from blocked or waiting threads. The curr...

Normally when one uses Java 8's parallelStream(), the result is execution via the default, common fork-join pool (i.e. ForkJoinPool.commonPool()). That is clearly undesirable, however, if one has ...

Question As Fork-Join seems to be the current hype and recommended in many answers, I thought: why not do some research on how fast it actually is? To measure this, I wrote a small program (see c...

I understand that there is overhead in setting up the processing of a parallel Stream, and that processing in a single thread is faster if there are few items or the processing of each item is fast...

Here's my understanding of the Stream framework of Java 8: Something creates a source Stream The implementation is responsible for providing a BaseStream#parallel() method, which in turns returns...

In Scala you can use a global ExecutionContext if you don't need to define your own by importing scala.concurrent.ExecutionContext.Implicits.global. My question is why ForkJoinPool was chosen for ...

I have a custom ForkJoinPool created with parallelism of 25. customForkJoinPool = new ForkJoinPool(25); I have a list of 700 file names and I used code like this to download the files from S3 in...

I want to submit Runnable tasks into ForkJoinPool via a method: forkJoinPool.submit(Runnable task) Note, I use JDK 7. Under the hood, they are transformed into ForkJoinTask objects. I know tha...

I need to block threads on ForkJoinPool when its queue is full. This can be done in the standard ThreadPoolExecutor, e.g.: private static ExecutorService newFixedThreadPoolWithQueueSize(int nThrea...

I read a great article about the fork-join framework in Java 7, and the idea is that, with ForkJoinPool and ForkJoinTask, the threads in the pool can get the sub tasks from other tasks, so it's abl...

I'm procesing data using latest Java 8 lambdas with parallel streams. My code is following: ForkJoinPool forkJoinPool = new ForkJoinPool(10); List<String> files = Arrays.asList(new String[]{...

My program searches for a solution (any solution) to a problem through a divide-and-conquer approach, implemented using recursion and RecursiveTasks's: I fork a task for the first branch of the div...

I have a recursive divide and conquer algorithm that requires two computationally intensive base case tasks before starting the dividing. The initial base cases are independent tasks, so I want to ...

What I want I want to work on optimization of fork/join algorithm. By optimization I mean just calculation of optimal number of threads, or if you want - calculation of SEQUENTIAL_THRESHOLD (see c...

After looking the Fork/Join Tutorial, I created a class for computing large factorials: public class ForkFactorial extends RecursiveTask<BigInteger> { final int end; final int start; pri...

We're making some good progress in load testing and scaling an akka application but we're seeing scala.concurrent.forkjoin.ForkJoinPool.scan() coming up as the second highest hotspot around 20% of ...

What is the key difference between Fork/Join and Map/Reduce? Do they differ in the kind of decomposition and distribution (data vs. computation)?

I have got the following class which runs and compiles (you can try it out). The only thing puzzles me a little is that at the end in the main it works fine with fj.invoke(task) but it does not wit...