Questions tagged [multithreading]
Multi-threading related questions including technique, structure, and safety issues.
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Multithreaded processing of single REST requests
Background:
We're prodiving an API that provides information about all users within a given group. Our API is a high level fascade over another low-level REST API.
To gather those information we first ...
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4
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3
answers
301
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N threads enter, one and only one should do extra processing that others wait for
My task is, I think, pretty interesting, if a bit unusual. Any number of threads can call function f(). They add some data to a buffer and begin waiting (the function is blocking). Eventually some ...
- 284
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8
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What causes unpredictability when doing multi threading
Multi threading could cause a racing condition if two threads are accessing the same memory slot, but why is that? From a HW point of view, if the two cores are designed the same, internal pipelines ...
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2
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127
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Low-Latency Data Sharing Between Threads in C++: Options and Considerations
What are the most efficient and low-latency approaches for sharing data between threads in a C++ system, and why? My primary concern is minimizing latency and maximizing performance, as I have two ...
6
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1
answer
286
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Can functional programming languages have deadlock conditions?
I am reading through "Clean Architecture: A Craftsman's Guide to Software Structure and Design" and it says that:
All race conditions, deadlock conditions, and concurrent update problems are ...
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Difference between outcome of using mutex/spinlock/semaphore in this deadlock situation?
I'm not sure if my answers to the following exercise is correct:
Suppose the program is run with two threads. Further suppose that the
following sequence of events occurs:
Time Thread 0 ...
- 11
0
votes
1
answer
122
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Reducing contention/locking in a job system involving read/write dependencies?
I have a job system that has two different types of dependencies per-job:
Jobs can rely on other jobs to be completed first, but this is optional
Jobs have read/write dependencies (shared/exclusive) ...
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0
answers
434
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How does Spring boot and Postgres handle the concurrent updates?
I want to understand how does Spring Boot and Postgresql DB handle the concurrent requests for updating a value in DB. Consider this example of facebook likes, if there are multiple instances of ...
3
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2
answers
766
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When should one utilize Atomic Operations?
I have never used atomic operations, and remain largely ignorant of how to utilize them. And yet, I often come across objects like this when peering into Qt's backend:
https://doc.qt.io/qt-6/...
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77
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If you run a function in a different thread, but you wait for it to finish in your main thread, is that function asynchronous?
Backstory
Probably a stupid question, but I just have a sneaking suspicion that "asynchronous" is the wrong terminology to us for naming my template function here:
template <class T>
...
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1
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119
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Design of A Multithreaded Simulator
When designing my simulator, I have gotten stuck on 2 main design choices.
The simulator can be described as having X number of nodes (between 50 - 2000) that each need to independently do some ...
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2
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88
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Multi-threaded design for continuous messages analysis
Since I don't have much knowledge of multi-threaded design and English is not my native language, I don't know how to exactly describe my problem.
Let's say I have a mini-program in school, which has ...
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1
answer
200
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Best way to accept a lot of user input from command line
I have a program that accepts computer names and then will perform CIM session tasks. The computer names are passed in from the user input and separated by "," (ex: program.exe -computers ...
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33
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7
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7k
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Why do modern operating systems *ever* have perceptible input (keyboard/mouse) lag?
Sometimes computers stutter a bit when they're working hard, to the point where the mouse location freezes for a fraction of a second, or stutters intermittently for a few seconds. This sometimes ...
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Do I really need TaskManager class? [duplicate]
Background:
I'm coding an app, the core idea is simple - I can choose a 'Task' (consists of name, code to perform aka Runnable, progress) through GUI, start it, stop it, start all 'Task's and stop all ...
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2
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165
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Accessing Hardware-based resources from multiple worker threads
I have a technical application that interacts with different hardware components: measurement devices, sensors, custom hardware. These use dedicated interfaces like USB, serial ports, TCP/IP ...
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1
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1
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202
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Shared mutable object in Multithreading
I have a class like this. (My actual class is different. I am using this to explain the problem). This class instance is shared between 2 threads.
However those 2 threads (thread1 and thread2), call ...
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1
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What is the benefit of equipping a computer or smartphone with multiple CPU cores that differ in clock speed? [closed]
I've bought a samsung galaxy s21 ultra about a year ago. Today i was looking at the specs again and i noticed that the Samsung Exynos 2100 processor consists out of 1 single CPU core of 2.9 GHz, three ...
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Do datacenters have conditions that might throttle component clock speed (either intentionally or automatically)?
Here is the question.
On a 2.2 GHz processor with 6 physical threads and 6 hyperthreads, I see performance on the order of 3-10s for a particular job involving OpenCV.
I do not specify that the ...
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2
answers
434
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What happens when one thread is waiting to be executed while another is waiting for input?
Suppose I have two threads, A and B. A is waiting for input, while B is waiting to be executed. All other CPU cores are busy with CPU-bound tasks.
What will happen to A?
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4
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1
answer
245
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One producer - multiple consumers queue, best way to guard against rare duplicates?
I have a classical one producer - multiple consumers queue, each item can be processed independently. On rare occasions (<1%) there can be multiple queue items related to the same object the ...
1
vote
3
answers
332
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Lockfree customer producer problem
We have following class:
class ProcessStore
{
ConcurrentDictionary<int, MyDisposableClass> _processes = new();
bool _disposed;
void Store(int Id)
{
if(_disposed) { throw; }
...
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2
votes
1
answer
102
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Design for deduplicating concurrent tasks in flight simultaneously
I have 1-20 agents that issue requests over time with roughly ~50 in total in flight at any given time. Many of these requests are identical. The tasks are idempotent, but if two identical requests ...
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1
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840
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Run lambda inside a separate thread with a member variable caught by reference
So, I have the following two functions in THE SAME class:
void start()
{
...
m_pRunnable = createRunnable(
[spDiskManager = m_spDiskManager,
path = m_path,
&success =...
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0
votes
1
answer
754
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C# Kafka Consumer design
I have a C#-based system that works relatively well. It reads data from kafka, processes the data and then writes it out to MSSQL.
The kafka topic has been partitioned into 10 partitions - and after 2 ...
10
votes
8
answers
2k
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Why is there a shift towards asynchronous and event driven programming?
My question will be mostly about Linux and contemporary X86 hardware.
Clarifying the terms
async event based programming: spawning fixed amount of threads and using some user space scheduling ...
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3
answers
175
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Critical section with two different "rights of way" [closed]
In C#, how do I handle critical section with two different "rights of way"?
Theoretical use case: imagine a swimming pool (the resource). Many individual swimmers (worker threads A, B, C, ...
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2
votes
1
answer
208
views
Make multiple data structures thread safe without multiple mutexes
In my application, I have a class which I call a "Signal" (Think Qt signals if you are familiar with that) that represents a one-to-many connection. Objects can register handlers to the ...
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18
votes
3
answers
3k
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How do you test and demonstrate that you have properly prevented a race condition? [duplicate]
Suppose I'm building a web application using Django. Some of the views need to touch multiple database tables or rows, and there is some kind of state consistency that I need to ensure among the ...
- 335
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159
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Multi-threading optimization in-depth
A time ago I participated in an interview process where I was tasked with a simple requirement. I created the best solution I could, using some lock-free implementation.
I didn't pass the code ...
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vote
2
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364
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Event ordering/ race condition
Here's a scenario I need help with.
Say you have a dating app (distributed, multiple instances), that has a table likes
| id | user_id | liked_id |notification_sent|
If User A likes User B
Insert ...
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3
votes
2
answers
316
views
Does creating one thread per event subscriber scale well?
I'm working on an application implemented in different microservices, which uses a message broker (event bus) to consume events (simple pub/sub).
As for now, in a given microservice, we are spawning 1 ...
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4
answers
2k
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What will you do if multiple users access your application at the same time?
I'm an experienced Software Engineer but very weak in concurrency because of no prior experience in that. I've been interviewing with several companies in which I was asked similar kind of questions ...
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1
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214
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Does it make sense to spawn request driven jobs in a thread or process?
I've developed a large application that performs jobs, such that it receives input x and outputs y. For this application, speed is the top priority. The application is capable of running concurrently. ...
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1
answer
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Does native async implementation in languages like Python and C# Solve the "Free Lunch is Over" problem? [closed]
A while ago Herb Sutter wrote The Free Lunch Is Over: A Fundamental Turn Toward Concurrency in Software which I basically interpret to mean that, in order to improve performance, software engineers ...
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1
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307
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Asynchronous Server in C++
We are looking to develop an asynchronous server in C++. We are coming from C#, which has built-in support for async-await networking. However, with C++ it appears as if it is basically mandatory to ...
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designing high throughout system for storing hundred thousands incoming records per second in SQL server database
In our company we have a requirement where we would like to store hundred thousands incoming records per seconds. we currently a pub-sub model for processing many records(100/sec) from many system(~...
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5
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1k
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How can you ensure order of execution in concurrent tasks?
Here is what I am specifically doing:
I have a thread-safe queue
One 'write' thread constantly writes to the queue with data that comes from another service
Multiple 'read' threads take from the ...
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votes
1
answer
347
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Is Epoll/Multiplexing suitable to make network requests instead of "listen to" incoming requests?
I'm studying asynchronous IO, concurrent models for IO and how things works on windows, linux and most used web frameworks.
I'm struggling on understanding why single-threaded event loops like the one ...
1
vote
1
answer
251
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java threading model for scale up
I need some advice on the scale-up issue. we have a java application currently it works as below
the current system is using the Thread Per Request Model.
each client connection (long-running and ...
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2
answers
2k
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What is a "lock ordering inversion"?
I am looking into Eric Lippert's answer to this Stack Overflow question.
In his answer, he uses the phrase "lock ordering inversions" in regard to deadlocks. I've searched the web and have ...
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3
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109
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Is it better (or preferred) to initialize allocate and free structures used by a thread, "inside the thread"
Let's say we are building a threaded program in C, for example a message queue system where a thread is spawned to manage one end of the queue, and (re)connect sockets.
This can roughly be set up in ...
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How should a client handle receiving data from a separate thread?
There are plenty of tutorials on the internet on how to build a server that handles its clients through the creation of separate threads, but there is no tutorials (at least I couldn't find any) on ...
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141
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Is background long running thread a good choice for disk IO?
I am building a storage engine software that allows concurrent data writing, now I have two different choices here:
Method 1. Background Long-Running Thread
Multiple user threads write to their own ...
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2
answers
536
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Approaches of splitting the same type of work among multiple threads in C++
I have a reinforcement learning project.
For this I created a vectorized environment in C++, which is a handler for multiple instances of a simple game.
It is highly parallelizable. Each worker can ...
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3
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284
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Do multiple software-threads on a single hardware-thread system execute sequentially?
I understand that if a system consists of multiple hardware-threads the scheduler
assigns software-threads to hardware-threads.
However, hypothetically, let's imagine a system that does only consist ...
0
votes
1
answer
137
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Thread-Safety with Enumerable collections and copies
Imagine I have an interface IHeapObject:
interface IHeapObject
{
string Id {get;}
SomeEnum Type {get;}
}
and it's implementation HeapObject:
class HeapObject : IHeapObject
{
public string ...
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2
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356
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"Threads should only block on one thing" - is this a common best practice?
Context:
Recently I was discussing the design of a small programme with a new team member (I am the product manager). The programme is essentially a protocol converter that reads data from a number of ...
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How do social media platforms stay up-to-date with messages and posts? [closed]
This is a question I have always wondered
Is it as simple as repetitive pinging of a server in a seperate thread or is it more complicated than that?
I am only talking about the app version not the ...
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4
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2
answers
679
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Hexagonal/Clean Architecture - threads, locks, synchronization
All the examples across the internet try to pretend that every application is run on a single thread. There is no problem with synchronization, multithreading etc. Uncle Bob, in his "Clean ...
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