Questions tagged [concurrency]

In computer science, concurrency is a property of systems in which multiple computations can be performed in overlapping time periods. The computations may be executing on multiple cores in the same chip, preemptively time-shared threads on the same processor, or executed on physically separated processors.

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A ktor/Kotlin server which generates Discord profile banner images

I wrote my first project with ktor, it generate a nicely layout image with your Discord account information and current activity on Discord - in real time. I mainly write Python code and rarely any ...
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Is my non-blocking collection actually thread-safe?

I've implemented this out of curiosity, and I'd like to know if I've implemented everything correctly, and/or see if anyone has suggestions. This caches some metadata for a game, so: Infrequent ...
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"streaming" messages to a broker from a batch-like source (eg sql database), optionally acknowledge back to the source

I am writing library code to help other developers send messages to a pub-sub event broker. In many cases, the message source will not be "stream-like". Specifically, most messages are ...
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Correct synchronization of reads and writes to ConcurrentHashMap and ConcurrentLinkedQueue

I am writing a web application (Servlets, JDBC, no Spring - for learning purposes) that accepts orders from customers, while registered couriers can choose which one of these orders they want to ...
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Rust program to create mail.tm accounts

I have created a rust program to create https://mail.tm accounts, but I think there are things I could have done better. Are there things I can do to improve performance? Are there any unnecessary ...
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Are nested calls to `asyncio.gather()` dangerous?

I wrote this ~100 line script recently, where I tried out Python's asyncio library. When it comes to asynchronous programming in Python, I just have 2 days of ...
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2answers
99 views

Write deduplicated 9-digit numbers from concurrent clients to a log

Problem Statement: Write a server (“Application”) in Java that opens a socket and restricts input to at most 5 concurrent clients. Clients will connect to the Application and write any number of 9 ...
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109 views

PyQt load images in background process

I am building an application that needs to load 100-200 images (really only limited by performance) and display them to the user in a sort of gallery. A good analogy would simply be Google Images. In ...
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1answer
80 views

Intersect channels in Go

I have a simple golang app in which I have two background tasks that produce data,each of them use it's own channel to signal it produced another unit of data. I have a single consumer that needs the ...
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2answers
107 views

Generic concurrent bounded buffer in C

I just implemented a generic concurrent queue in C, and I'd like some feedback on my implementation, as well as the logic in handling generic data and concurrency. buffer.h ...
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154 views

Fixed-width non-FIFO DispatchQueue

I have implemented a custom concurrent queue on top of GCD which offers two additional pieces of functionality: Limit the maximum number of concurrently executing tasks. Give manual control over ...
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1answer
90 views

A tiny threads pool in C

I'm a newbie in C, and currently following Stanford CS107 - Programming Paradigms. For assignment 6, I find it'd be better to isolate the threads management from the service logic. The following code ...
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393 views

Single Producer Single Consumer lockless ring buffer implementation

I am writing a simple ring buffer for my own education. Below is a crack at a strategy described in http://www.cse.cuhk.edu.hk/~pclee/www/pubs/ancs09poster.pdf : Producer and Consumer keep local ...
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Parallelizing identical long-running tasks with Go channels

I have written a program in Go to compute the discrete logarithm mod primes (find \$x\$ such that \$h=g^x\mod p\$), and the algorithm I am using can be easily parallelized. Essentially, I am trying to ...
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2 Weeks into Go: Golang Tour WebCrawler Exercise

I'm on week 2 of learning go. I just completed the golang.org exercise on creating web crawler (https://tour.golang.org/concurrency/10) and I would please like feedback on my code. It feels overly ...
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1answer
77 views

Barging lock in Java

I found myself in need of a lock that allows my server to barge the write lock that might be acquired by my users. It would never interrupt them, but it would jump the line so the next time the write ...
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277 views

Parallelized web crawler using goroutines and channels

As part of the "a tour of Go" section on golang.org, I was trying to make a (formerly singlethreaded) web crawler parallelized using goroutines. I got it working but it doesn't seem to "...
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162 views

Thread-safe LFU Cache

I am trying to implement a thread-safe LFU cache algorithm, please review my code and would really appreciate some criticism or suggestion. (on naming, design, data structures used, anything) Some ...
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1answer
251 views

Thread-safe LRU Cache Implementation in Java

I am trying to implement a thread-safe LRU cache algorithm, please review my code and would really appreciate some criticism or suggestion. Some assumptions: capacity will be larger than 0 Some ...
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1answer
51 views

SHA256 password cracker - v2 with concurrency

I have updated my previous code with the suggestions. I have also implemented concurrency to speed up the results. I'd be interested for comments on a more efficient use on concurrency / parallel ...
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263 views

SO golang example with infinite for / channel workers

I whipped this up as an example of how infinite loops can often be used to great effect in golang, and also to discuss closing channels and worker communications. It was strictly off the cuff, but I ...
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Waiting for goroutines to finish

I have a program that starts a bunch of goroutines, feeds them data and when there is no more data, waits for the goroutines to finish. I use sync.WaitGroup. I am unsure if I am using correctly, in an ...
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1answer
128 views

Speeding up I/O bound python program

I have the following program. I have 90 million domain names split between 87 files. I need to resolve the IP of all. Right now I feel like this is super slow. ...
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1answer
68 views

A Concurrent Tree implementation with consistent snapshot capability

I have a tree in my application from which I need to periodically take a snapshot. I've been using locks so far, but after running into a few deadlock issues I decided to create a lock-free ...
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154 views

Concurrent Web Crawler

Description As an exercise of learning go concurrency patterns, I decided too build a concurrent web crawler. I made use of the argparse module I put up for review a while back. I'm looking for ...
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1answer
65 views

Concurrent dependant routines in a gui application

The idea is that, in my application I have 5 routines named long_process_1, long_process_2, ...
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1answer
59 views

Keep reading user keyboard input if available, while echoing back the latest available

On StackOverflow I have asked a question a few minutes ago, but then by trying a bit more, I found the answer myself, and I'm posting the resulting working code here for review. What the code does, is ...
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Game of Life, thread per cell

In an effort to learn Java's support for concurrency I solved a self-imposed exercise to write a Game of Life simulator in Java, running a separate thread for each cell. Here is my code: ...
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35 views

Orchestrating an unknown number of goroutines

I recently wrote a piece of code to parallelise some code with goroutines and I was wondering if I could get some feedback. It looks overly complex... but I'm not sure how I could make it simpler. It'...
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1answer
158 views

A concurrent lock-free Linked Queue implementation

Recently I've been learning about concurrency/parallelism and I decided to implement the Michael&Scott lock-free Linked queue (PDF) as practice. I'm not entirely sure how to test this data ...
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253 views

Dining philosophers problem in Go

I'm new in Golang and haven't done concurrency in a bit. I would love to hear your opinion on my Dining problem Go solution. Description here, with a tl;dr below: Five silent philosophers sit at a ...
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37 views

n executions of a periodic goroutine

I'm new to Go and have a use-case for periodically executing an async work-function. I want the interval between work-function executions to be constant (not the time between one finishing and the ...
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110 views

Implementing GSL synchronized_value

Core Guidelines mention a type synchronized_value<T>, which supposedly pairs std::mutex with the internal value. I couldn'...
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1answer
47 views

Concurrency mechanism for ensuring repeated threads are executed in a given order

Inspired by the following leet-code Suppose you are given the following code: ...
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1answer
464 views

Reading one source Stream by multiple consumers asynchronously

The problem was using single Stream from the HTTP response in multiple consumers simultaneously. For example: while data is loading, I want write it to the some ...
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52 views

Why is my Python thread pool faster than my Go worker pool?

I have recently been digging into understanding Golang concurrency, in particular the use of channels and worker pools. I wanted to compare performance between Go and Python (as many have done) ...
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39 views

Run non overlapped periodical tasks on user specified executor

I have concurrency tasks in my module: user code is able to instantiate my object and specify Executor service, then user can submit requests to this object which ...
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1answer
349 views

Concurrent Queue with enqueue and dequeue using Stack as underlying data structure

This is a mix of data structure and multi threading concept based question. (This is only for understanding and learning purpose) The language for the solution : Java A Queue with FIFO behavior needs ...
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1answer
364 views

C++ latch implementation

Since std::latch is not in many standard C++ libraries, I tried implementing my own, is it OK from memory ordering perspective or ...
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1answer
67 views

Command line dictionary tool, using webscraping

This is my first proper Go program, after completing Go by Example and https://tour.golang.org. I have a background in Python. This program scrapes definitions from Wordnik, then prints them nicely ...
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42 views

infinite generator with eviction

I made a struct that will loop through a list, and return the next element on calls to the Get() method. It also allows to remove elements from the list by calling the Evict() method, and is safe for ...
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1answer
371 views

Banking application - Optimizing java multi-threading code

I created a simple Bank application to make multiple transactions between multiple accounts. It is working as expected. But I want to know can I make the code more optimized. ...
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1answer
243 views

One consumer and two producers using threads

I have based this code on Producer-Consumer Threading on Real Python. The idea is that I have 2 producers: One producer will give result every 0.4 to 0.7 seconds, depending on REST call. The second ...
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28 views

Executing two database queries concurrently in Go [closed]

I would like to execute two database queries concurrently for quicker response time. Since channels seemed to be too verbose, I came up with the solution below. However, I'm not very confident about ...
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2answers
203 views

Simple multiple producer and single consumer concurrency pattern

Anyone please review and share your feedback for the following code. Multiple producers generate random integer numbers and a single consumer receives it to display only odd numbers out of it. ...
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1answer
437 views

A multi-thread Producer Consumer, where a Consumer has multiple Producers (C++17) - Part 2

This post is based on A multi-thread Producer Consumer, where a Consumer has multiple Producers (C++17). I am trying to build a Consumer that consumes data from ...
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3answers
2k views

A multi-thread Producer Consumer, where a Consumer has multiple Producers (C++17)

EDID: Thank you very much for your feedback. I updated the code and opened a new post for the updated version. See here. This post is loosely based on A multi-threaded Producer Consumer with C++11. ...
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Multi Threaded High Performance txt file parsing

EDIT A port of Björn's answer to C++ with further improvements at bottom achieving up to 2.4GB/s on the reference machine. Text file parsing and processing continues to be a common task. Often it's ...
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Hosted service for queuing and running tasks in parallel in ASP.NET Core

I am attempting to construct a background service for an IIS-hosted ASP.NET Core project that basically queues tasks and runs them, and I decided to go with the ...
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2answers
200 views

Recursive Mergesort using goroutines

When learning a new language, one of my first tasks I like to go through is writing a few different sorting algorithms in that language to help familiarize myself with the syntax and see if there are ...

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