Questions tagged [multithreading]
Multi-threading related questions including technique, structure, and safety issues.
637
questions
1
vote
2answers
40 views
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 ...
3
votes
2answers
168 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 ...
4
votes
4answers
369 views
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 ...
0
votes
1answer
37 views
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. ...
-4
votes
1answer
60 views
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 ...
0
votes
1answer
84 views
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 ...
0
votes
1answer
96 views
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(~...
4
votes
5answers
286 views
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 ...
0
votes
0answers
76 views
Multithreading vs Asynchronous game loop for multiplayer online game?
I'm trying to create a turn based multiplayer online game where players can be grouped in a room/lobby and play (similar to Ludo but number of players can be more than 4). There can be multiple such ...
0
votes
1answer
41 views
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 ...
0
votes
1answer
114 views
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 ...
7
votes
2answers
335 views
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 ...
0
votes
3answers
90 views
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 ...
-1
votes
1answer
58 views
How should a client handle receiving data from a seperate thread?
There are plenty of tutorials on the internet on how to build a server that handles its clients through the creation of seperate threads, but there is no tutorials (at least I couldn't find any) on ...
0
votes
1answer
58 views
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 ...
0
votes
2answers
132 views
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 ...
1
vote
3answers
144 views
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
1answer
66 views
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 ...
4
votes
2answers
232 views
“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 ...
-1
votes
1answer
109 views
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 ...
4
votes
2answers
289 views
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 ...
1
vote
1answer
62 views
In an MVC-patterned app, how should one build the interface between model and user interface layers to work nicely with threading?
I am wondering about this. This is a sort of follow-up to my last question here:
In the MVC pattern, what has the responsibility for creating the view?
because now I've run into the question of how to ...
0
votes
2answers
209 views
My aproach to lockless concurrency
this is a highly theoretical question about my parallelization approach.
First of all, I want to inform everybody that I do not claim that I am the 'inventor' of that approach but I couldn't find any ...
-3
votes
1answer
65 views
Will this time duration measurement in two threads give correct result?
A program I'm developing has two threads running similar but different task:
thread1:
timer1.start()
writeToExternalDB1(consumedData)
timer1.end()
thread2:
timer2.start()
writeToExternalDB2(...
4
votes
4answers
353 views
How to understand the first and second readers-writers problems?
Computer Systems: a Programmer's Perspective says
The readers-writers problem has several variations, each based on the priorities of readers and writers.
The first readers-writers problem, which ...
-2
votes
1answer
79 views
How should functions that keep state across multiple invocations be made safe?
In Computer Systems: a Programmer's Perspective,
12.7.1 Thread Safety
When we program with threads, we must be careful to write functions
that have a property called thread safety. A function is said ...
2
votes
0answers
93 views
Why does the Java CompletableFuture API uses long + TimeUnit instead of Duration?
Java 9 introduced many new methods in the CompletableFuture API that support execution timeouts.
For example:
public CompletableFuture<T> orTimeout(long timeout, TimeUnit unit);
public ...
0
votes
1answer
77 views
How to subscribe to collection edits happening in a different thread?
I'll be using C# for my example since this is what I am using, but the problem is sort of generic.
My app code takes a collection of Foos (externally populated and edited) to do some processing, and ...
2
votes
1answer
91 views
Effective thread usage under blocking scenario
I have the following scenario:
I am listening file requests and when one arrives, I am starting download task in a new thread. After download task ends, a process task starts but this is important, ...
1
vote
1answer
69 views
Multi threading a database driven service
First some background on the problem, we have a windows service (C Sharp) that receives new messages and processes them.It is database driven so it checks a table for unprocessed records, processes ...
59
votes
10answers
21k views
Does it ever make sense to use more concurrent processes than processor cores?
I've got some process in Go. Here's an example counting lines in text, though the question is meant to be far more general than this particular example:
func lineCount(s string) int {
count := 0
...
0
votes
1answer
46 views
System design to store pieces of data with specific ttyl to then refetch
I have a system which generates pieces of data that needs to be tracked and assigned a specific TTYL value (a value in seconds) for how long they are supposed to live before being re-processed.
I ...
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votes
1answer
105 views
How to do achieve parallelism in a console application
I have a .net web application, let's say A and a .net console application, let's say B.In A, I have a queue with multiple jobs to be done by B.Once I select the jobs from A, a queue gets created. Each ...
0
votes
0answers
29 views
Is JTA appropriate for concurrent loads to a single database and transaction?
I have a Java process that loads data from a file in to an RDBMS - basically a CSV import with some logic around updating and deleting records in addition to the inserts. It's important that it ...
2
votes
1answer
123 views
What is the best way to decouple and define the orchestration (coordination) of concurrent tasks?
I have a data synchronisation concurrent algorithm. It does the following: get data and files from server, send data and files to server, save them to database / filesystem. Imagine the system like ...
7
votes
9answers
4k views
Why is multithreading not used everywhere?
Not almost, but all modern CPUs have multiple cores, yet multithreading isn't really that common. Why to have these cores then? To execute several sequential programs at the same time? Well, when ...
1
vote
2answers
252 views
RxJava and race conditions
I have seen some RxJava projects using multithreading with .subscribeOn(Schedulers.io()), and their .subscribe(() -> {...}) code is manipulating some data structures that are also processed by ...
0
votes
0answers
132 views
How can you multithread an html parser [ in C++ and similar languages ]?
Ive done two HTML parsers.
Done with Regular Expressions [that accounted for nesting]. It was quick, but error prone.
Done by evaluating Character by Character through switches. Here was the basic ...
1
vote
1answer
77 views
How to represent this multithread application?
I am having trouble trying to represent some multithread process and I would appreciate some advice.
Please let me explain this with code. (in C++'ish because that is what I am familiar but ...
-2
votes
2answers
915 views
Generating unique numeric ids in multiple thread application without locking
Multi Threaded application with n threads implemented using ExecutorService.
There are x (tens of millions) tasks submitted to the ExecutorService.
Each task needs to generate millions (number of ...
-1
votes
1answer
207 views
Do other languages have variables shared between threads?
I guess it would be too complex for Node.js / JavaScript to leverage, but I've been working with clusters in node to break big tasks down so all cores can work at once but the inter-process messaging ...
-2
votes
1answer
364 views
How can I represent with UML a process that involves queues?
I would like to use UML diagrams to show some processes I am designing and would like to implement.
The processes involve using a queue, and adding and taking out elements from it.
In one of this ...
1
vote
2answers
385 views
Which UML diagram is more adequate to represent a multithread process with loops
I have a process that I have been able to drawn somehow with a flowchart.
This process involves several classes, loops and several threads of execution.
However I am unsure which (if any) UML ...
-3
votes
1answer
83 views
Methods for reliably benchmarking own program's run time
I'm writing a basic password cracker in C as an introduction to multithreaded programming. I've implemented this already using a 'parallelization' approach that spins up a set number of threads and ...
2
votes
3answers
240 views
Should services in a service layer be thread safe?
This is for an Android app, but I think the question applies to any software designed with a service layer.
Our app is structured with a presentation layer that handles the UI and a service layer ...
3
votes
3answers
447 views
How can I improve the speed of scanning multiple directories recursively at the same?
So I am trying to speed up my program by using concurrency and/or multi-threading and/or process parallelism. The topics are pretty complex and I am sort of new to them so I am still trying to figure ...
0
votes
1answer
72 views
Handling background tasks that may not be relevant when they are completed
Imagine the following pattern: you have a window with information that needs to be updated asynchronously. You launch and detach a thread to handle fetching the information, but while the information ...
2
votes
1answer
278 views
Long running REST API in PHP, async?
I have a RESTful API built with PHP. In POST request saving to DB is triggered. The problem is that now I have to support long running tasks. For example a user triggers POST request that is going to ...
0
votes
2answers
157 views
Worker pool running tasks of the same kind serially
I would like to run tasks in parallel. At this time, I am using a very simple
worker pool using a single concurrent queue shared by all the threads.
Every task has a non unique "tag" (an integer in ...
6
votes
5answers
1k views
Performance: Is There a Reason to Use Processes over Threads?
This is a general question but I work in the .NET world so I'd like to know if there any specific quirks about the .NET Framework / Core platforms that I should be concerned about here.
I think it's ...
