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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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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Pseudo-parallel depth-first search
I'm writing a small program that generates a file containing an adjancency matrix, it then reads from that file, constructs a graph and does something like a parallel depth-first search (dfs) on it.
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Concurrent Queue using Ada SPARK with the Ravenscar profile
See here: https://gitlab.com/linted/linted/blob/162b5e9fba53a90b3c6d78e214776e069c3c722b/src/ada-core/src/linted-queues.adb
The code implements a concurrent queue.
It can't allocate memory or use ...
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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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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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Drawing the Mandelbrot with multiple threads in rust
The code below draws the mandelbrot set for { z | z∈ ℂ, -2.2 ≤ Re(z) ≤ 0.6, -1.4 ≤ Im(z) ≤ 1.4} into a 300×300px png image. For each pixel,
if the sequence {zi} is found to ...
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An in-memory copy of the GDAX order book for an arbitrary cryptocurrency, updated in real time
GDAX is the cryptocurrency exchange owned and operated by Coinbase.
This code is intended to be the basis for an order-book-strategy trading bot.
I'd love feedback on my use of data structures, my ...
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ConcurrentLinkedQueue Object Pool implementation
I have implemented this simple unbounded ObjectPool based on a ConcurrentLinkedQueue of WeakReferences. I have a thread-unsafe object that is pretty expensive to create, and most of the time it will ...
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Custom ThreadPoolExecutor/ThreadFactory in order to submiting callables upon incoming ActiveMQ messages
I have a service that is subscribed to a specific channel of ActiveMQ.
Every time a message arrives the service has to start a "job" (submit instances of Callables)...
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Fast lock implementation using pipes only
For fun I wanted to create a lock implementation that was about as fast as one using futexes but that used used pipes instead and that queues waiters in user space instead of in-kernel. For the queue ...
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A mutex that can detect certain types of programming error
This mutex prevents concurrent access to a target resource. One key requirement is the ability to be acquired
in a (scheduler) thread and released in a different (worker) thread. Unfortunately this ...
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Golang function that reads S3 files and populates maps with strings as keys
I have a below read function which is called by multiple go routines to read s3 files and it populates two concurrent map as ...
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Order guaranteed recursive_transform template function implementation with execution policy in C++
This is a follow-up question for A recursive_transform Template Function with Execution Policy, A recursive_transform Template Function Implementation with std::invocable Concept and Execution Policy ...
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synchronized access to HttpSession attribute vs static ConcurrentMap with HttpSessionListener
As a part of library implementing websocket Guice scopes I need to maintain an object related to each HttpSession called ...
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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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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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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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Concurrency control between a non-blocking and a blocking methods
In this program, there is a list of Holders that is managed by a singleton class. Each of the Holders keeps a copy of the ...
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Linked list with hand-over-hand locking
Follow-up to this question: after reading the comments, I decided to redesign my linked list to have a cursor that only contains one node and implement the interface similar to the one of forward_list ...
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Override prototype inside of constructor of ES6 class for dependency injection
We implemented a small dependency injection mechanism which we use in our project. Now after 2 years of developing our project we need our classes to know who instantiated them via dependency ...
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Python coroutines to write files
I'm refactoring a monster 176-line function into something more sensible and more testable. The function as it stands fails the 'one thing and thing well' test by doing many things:
Indexing through ...
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Concurrency using immutability
I was watching the following video about software transactional memory(using a package that maintains an access log). At the moment I am trying to learn about concurrency with shared memory and ...
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Implementing non-blocking Executor.map
I wanted to extend concurrent.futures.Executor to make the map method non-blocking. It seems to work fine, but I would be very ...
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Concurrent AWS S3 copying of images listed in MySQL
I created the following one off script and it did the task quite well (1000s of requests / second with low CPU usage - outperformed the previous python script in every aspect). But I am wondering if ...
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Creating an observable stream of clicks and converting it to an iterator
Problem 1
StratifiedJS allows people to cleanly create observable streams using the Stream class from sjs:sequence:
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Golang: reading and writing files in parallel
I am trying to read a big file line by line, inspect and cleanse each row and write to either of two output files depending on the outcome. I am using channels for this. I am still quite new to this ...
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Methods to add and check elements in a Bloom Filter
I have a working Java implementation of Bloom Filter.
These are the methods to addElement and check for an element.
...
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Concurrent resizable ring buffer
I'm trying to find the fastest way to enqueue and dequeue items concurrently in Go.
There are some restrictions:
it needs to be unbounded
Memory allocation should be low
Multiple producers
(Single ...
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3
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TimeoutManager: check whether a task has been finished within a given time
I want to make a helper class, which raises an event whenever something is not finished in a certain time.
Example: my program sends out multiple network messages concurrently. After a random delay, ...
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Parallelized Web Crawler
Exercise is here:
https://go.dev/tour/concurrency/10
Prompt:
In this exercise you'll use Go's concurrency features to parallelize a web crawler.
Modify the Crawl function to fetch URLs in parallel ...
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508
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Parallel Breadth First Traversal in Rust
Overview
I have been writing my own graph API for Rust and one thorny problem I wished to tackle was a
parallel breadth first traversal of the graph. The API itself will have different graph
flavours, ...
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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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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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Concurrent execution and coordination of C# tasks
I have a class, 'TaskCoordinator' which has 'BaseTask's applied to it.
The BaseTasks have OnStarted, OnFinished and OnCancelled events which are triggered to notify the calling class of their events....
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Comparing Java Semaphore versus ReentrantReadWriteLock
In this post, I attempted to compare the performance of two concurrency constructs:
java.util.concurrent.Semaphore,
...
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Many-readers-one-writer with semaphores and multithreading
I've been looking for a solution to the may readers one writer in Java.
I was intrigued by this question posted here and I read the Wikipedia entry about it.
So far, I've reached a fine solution, or ...
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Golang gRPC context to check if cancelled or if deadline is exceeded while running function code
I am writing a gRPC Golang application and am looking for the best way to check if the deadline is exceeded or if the client cancelled the call.
On the server side I created a channel called ...
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Comparing performance of multi- and single - thread search of a maximum number
I have a class that compares the performance of two methods (multi- and single- thread) that searches for maximum number in the string of numbers. I want to improve the performance of a multithreaded ...
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668
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Concurrent hash map implementation with Go's channels
I've implemented a concurrent hash map in Go. I'm fairly new to this language as I have mostly Python background so I'm looking for suggestions how to improve my code. I've ran the tests with ...
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Pub/Sub Broker Subscriber Interface
I'm working to build out a Subscriber interface for handling at-least-once messaging semantics, so I can produce different brokers. Here's my interface thus far:
<...
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Golang: Improving communication between workers
Came back to the software side of my night vision security camera project after taking some time to learn about electronics and I found it a bit hard to retrace the logic of my program.
I have a ...
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Using blocking queue to calculate data stream - Generalized
A followup on my previous question Using blocking queue to calculate data stream. This time suppose we have a list of blocking queues as stated in the following manner:
Suppose you have a list of ...
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637
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Producer / consumer pattern with limits on .NET
For a project that I'm developing, I need to implement the producer/consumer pattern, but the quantity of consumers cannot be higher than some number (say 40).
I created a concept project on GitHub ...
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Concurrent ObjectPool using ConcurrentLinkedQueue
Main ObjectPool Class: It uses atomic operations and a concurrent linked queue to achieve the best performance compared to Apache commons pool. I want to make sure there are no concurrency issues even ...
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RCU in C++11 using std::shared_ptr and a little more
Here's some code I wrote to solve a problem at the server I'm working on. Is this valid? I've tested it, and it works, but I would like some opinions on this.
It's basically a ...
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Frequency of words in all files of a directory using Future - Scala
I created a program to get frequency of word in all files in a directory using Future API
...
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Implementing a long-running entity lock
Requirement
I have an entity named ImportData which can be processed once in order to extract data from a file fed to the application.
I need to make sure that, in ...
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Parallelized image transformations using GraphicsMagick
This is part of a script that I use for porting a TWRP theme from one resolution to another, respectively portrait to portrait and landscape to landscape. In this function entirely, it focuses on the ...
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Porting Java semaphore to MacOSX
I wanted to write some more JNI code and decided to (re)implement a semaphore for MacOSX. In order to assert somehow correctness of my implementation I hereby supply a (multi)consumer/(multi)producer ...
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