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Questions tagged [multithreading]

For questions regarding multi-threading, the ability of a computer or a program to perform work concurrently or asynchronously by utilizing multiple concurrent streams of execution (generally referred to as threads).

Multi-threading is a common model to implement SM in multi-cored machines, where threads share memory through shared variables. In this model in parallel programming a processor can create multiple threads that will be executed in parallel. Each thread has its own stack, variables and ID, considered private state. For every thread there is a unique heap shared by all, then considered shared memory.

In order to allow a volume of work to be most effectively and safely divided into multiple concurrent streams of execution, a number of critical areas need to be addressed.

  • Scheduling: ensure worker tasks are able to progress independently and effectively (e.g. deadlock/livelock avoidance)
  • Publication: ensure data altered in one thread is only visible to others as expected
  • Synchronization: ensure critical regions are protected from multiple concurrent updates causing data loss/corruption.

The underlying tenet of concurrent processing is Amdahl's law (graph). This law governs the diminishing amount of throughput that can be achieved by greater numbers of concurrent processors/cores. Therefore the overall aim of multi-threading is to minimize the amount of serial execution (exclusive locking) within any concurrent system.

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139166 questions
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C# equivalent to Java's Thread.setDaemon?

How do I set a thread to a daemon thread in C#?
Epaga
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How to cleanly exit a threaded C++ program?

I am creating multiple threads in my program. On pressing Ctrl-C, a signal handler is called. Inside a signal handler, I have put exit(0) at last. The thing is that sometimes the program terminates safely but the other times, I get runtime error…
rjlion795
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Java ExecutorService: awaitTermination of all recursively created tasks

I use an ExecutorService to execute a task. This task can recursively create other tasks which are submitted to the same ExecutorService and those child tasks can do that, too. I now have the problem that I want to wait until all the tasks are done…
Christoph
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How do the C++ STL (ExecutionPolicy) algorithms determine how many parallel threads to use?

C++17 upgraded 69 STL algorithms to support parallelism, by the use of an optional ExecutionPolicy parameter (as the 1st argument). eg. std::sort(std::execution::par, begin(v), end(v)); I suspect the C++17 standard deliberately says nothing about…
Scott Smedley
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Is Ruby's stdlib Logger class thread-safe?

In short, is the standard library Logger class in Ruby thread-safe? Only useful info Google turned up was someone on a forum saying it "seems" thread-safe. And I don't feel like spending time testing a logger to try to figure out if it is or…
jimeh
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C++: Static variables in multithreaded program

What is the problem with having static variables (especially within functions) in multithreaded programs? Thanks.
user542687
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5 answers

Using string as a lock to do thread synchronization

While i was looking at some legacy application code i noticed it is using a string object to do thread synchronization. I'm trying to resolve some thread contention issues in this program and was wondering if this could lead so some strange…
Illuminati
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Do mutexes guarantee ordering of acquisition? Unlocking thread takes it again while others are still waiting

A coworker had an issue recently that boiled down to what we believe was the following sequence of events in a C++ application with two threads: Thread A holds a mutex. While thread A is holding the mutex, thread B attempts to lock it. Since it is…
Jason R
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How to properly release an AVCaptureSession

I'm using the AVFoundation classes to capture the live video stream from the camera and to process the video samples. This works nicely. However, I do have problems properly releasing the AVFoundation instances (capture session, preview layer, input…
Codo
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Nvidia graphics driver causing noticeable frame stuttering

Ok I've been researching this issue for a few days now so let me go over what I know so far which leads me to believe this might be an issue with NVidia's driver and not my code. Basically my game starts stuttering after running a few seconds…
TylerGlaiel
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Android Instrumentation Testing - UI Thread Issues

I am trying to write an Instrumentation Test for my Android app. I'm running into some weird threading issues and I can't seem to find a solution. My Original Test: @RunWith(AndroidJUnit4.class) public class WorkOrderDetailsTest { @Rule …
Khalos
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Thread.Sleep(0) : What is the normal behavior?

To my understanding a Thread.Sleep(0) force a context switch on the OS. I wanted to check what was the maximum amount of time that could pass in an application before to receive some CPU time. So I built an application that does Thread.Sleep(0) in a…
Benoittr
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difference between Thread and Handler

Can somebody tell me the deference between Thread and Handler? When we use Thread and when we use Handler? I have two code in my project , But I can't understand them. final Handler handler = new Handler() { @Override public void…
Khodayar
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Threading error when using `ActiveRecord with_connection do` & ActionController::Live

Major edit: Since originally finding this issue I have whittled it down to the below. I think this is now a marginally more precise description of the problem. Comments on the OP may therefore not correlate entirely. Edit lightly modified version…
button
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What is the Java Equivalent of C# "Logical Call Context"

In .net, there is an "uber" thread-local-storage (TLS) which allows arbitrary TLS data to auto-magically "jump" from one thread to another. It is based on the CallContext class. In other words, a logical request can spawn a hierarchy of new…
Brent Arias
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