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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Java Concurrent Multimap
I've implemented a concurrent multimap that support concurrent put and remove but I'm unsure of its correctness. I would appreciate your feedback.
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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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Pausing and resuming a concurrent database update queue
I have a class DatabaseQueue which asynchronously runs SQLite updates that it takes from a LinkedBlockingQueue.
I implemented a ...
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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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Thread-safe BitArray
Notes:
supports 64-bit platforms only
ulong used where negative values make no sense
library functions are assumed to be correct (whether they actually do what I ...
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Dynamically extensible threadpool implementation in C
Purpose
For my recent project, I needed a thread pool. I saw a lot of implementations at GitHub, but most of them were quite complicated. With complication comes performance penalty. Most importantly,...
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Thread safe ConcurrentDictionary wrapper
I needed some features that ConcurrentDictionary doesn't have (such as a maximum number of items) so I created a wrapper around it.
This is my first time working ...
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Answering Master Clojure for the Brave and True - concurrency exercises
I recently answered the two exercises at the end of this chapter of Clojure for the Brave and True (see the end of the page).
First exercise: count words in random quotes (in parallel)
This is my ...
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Limiting the maximum amount of goroutines run simultaneously
Here is my code which helps me to contol the maximum amount of goroutines run simultaneously.
In example below maximum is 5.
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HackerRank challenge to count ways to climb a staircase, solved using Java Fork Join
I'm trying to solve Stair case recursion problem on HackerRank. The problem is to find all possible ways for a child to climb a stair case with height n given that ...
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ConcurrentHashQueue in C#
The ConcurrentHashQueue data structure is a FIFO queue that at the same time allows look-ups of items based on a key in O(1) like a dictionary. It can be used as a ...
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Work stealing queue
I implemented work stealing queue inspired by Sean Parent's talk on code::dive 2016. Full implementation is here. I am looking to get feedback on improvements to make code more effective and common ...
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Golang concurrent writer
I wrote a program that concurrently reads multiple files and makes a request to an API for each line of each file. The JSON response is then parsed and the "available_filters" field is extracted. The ...
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Sum and stock size concurrent code using Executor
The code should parse the input values and calculate the sum and size of particular stocks, using Executor thread pool by dynamically adding the thread count.
Please review the following code for ...
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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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Find pairs of consecutive numbers fetched from blocking queues
I was coding for the following programming question:
Suppose you have two independent blocking queues that will keep getting new data, the new data will always be greater than the last element of ...
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Matrix multiplication with OpenMP parallel for loop
I tried implementing matrix multiplication with parallel for loop in OpenMP as follows. It runs correctly but I want to make sure if I'm missing anything. How does this determine the number of threads ...
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Concurrency-safe stack implementation in Go
As Go doesn't come with a lot of collection structures, I've implemented stacks myself, building off some sample code I found floating around. I've then tried to extend it further by:
Making a "...
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Recur-ratively resolve dependencies and summarize all results
I've been tasked with resolving all dependencies to a project. Because it couldn't be simple (it never is, right?), the requirements include a few different dependency management tools. For a first ...
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Task Wrappers for starting operation only if previous task has finished
I've written these two wrappers around Tasks, to help with common scenarios in our code where methods are called repeatedly, even if the previous operation hasn't completed yet. There are two common ...
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Blocking queue implementation with std::unique_ptr
I implemented, somewhat closely based on this implementation, a blocking queue with emphasis on filling up first. So if one producer and one consumer thread are using the queue, the producing queue ...
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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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The dumbest (futex-based) mutex
After reading Ulrich Drepper's "Futexes are Tricky", I have written the following "dumbest mutex" in C++14 using the Linux futex primitives. This mutex is simpler ...
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Producer - multiple consumer implementation using futures
I've tried to implement a producer-multiple consumer pattern using futures and I was wondering should it ever deadlock, and if it should, why?
I have this method ...
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Delegating ExecutorService implementation requiring only an Executor
I occasionally find myself needing to run code on some arbitrary thread or pass a Runnable to some arbitrary consumer, and missing the full functionality of java.util.concurrent -- for instance, ...
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Polling an API endpoint with timeout using channels
I have written a simple API client for my app in Go.
The client is very simple, it wraps http.Client and has some convenience methods.
The one method I am trying to get some feedback on, does ...
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Thread-safety based on object value
I need to create thread-safety on a Web-API method, but only when two requests containing the same property value are ran simultaneously.
I have created a mix of WaitHandles and a ...
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Java Matrix multiplication using Multithreading
I am trying to achieve matrix multiplication using the concept of concurrency and cyclic barrier.
Here is the code snippet:-
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Send multiple broadcast to multiple listeners
I want to send multiple broadcast to multiple listeners in go.
I can't send data through a channel, because only one listener will get it, except for the close ...
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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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Call third parties in parallel
I am trying to speed up some reporting on all employees but I am having difficulty determining where the "proper" place to parallelize my tasks. In order, this is what my code is currently doing.
Ask ...
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Thread-Safe Task Queue Implementation
Purpose:
This class exists to ensure actions created from other threads are executed in a synchronous manner. Additionally, it provides functionality to add actions that run after a delay.
Code: (...
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C++11 Blocking connection pool with auto release
Relatively new to C++. Please help me understand the potential issues with the following blocking object pool.
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Link checker using Go channels
I've started to learn Golang and channels in it.
I decided to write simple application - recursive link checker. Given some URL it tries to retrieve pages, parses them and goes deeper.
Here's a code ...
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Concurrently reading a Map while a single background thread regularly modifies it
I have a class in which I am populating a map liveSocketsByDatacenter from a single background thread every 30 seconds inside ...
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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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canonical pattern for transactional library state manipulation
In golang I am finding that there is a definite pressure in the language itself and built-in libraries to do things in a canonical way. Please can someone critically look at these two ways I am ...
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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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Simplified LogService (from concurrency in practice) with shutdown feature
Brian Goetz provided following code of LogService with shutdown feature:
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Repeat operation if signal is received
I have a data synchronisation operation that is observing a database. This is a fairly key piece of code for the system, so I want to make sure I handle the concurrency correctly.
The problem
The ...
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Concurrency and locking in a chat server
I've never done concurrent programming before, but I've written one using go channels and RWMutex, but I'm not sure if my approach is idiomatic. I feel like it could all use channels (Maybe).
The ...
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JUnit assertion for concurrency test
I'm learning Java concurrency by a TDD approach. Therefore I wrote a basic test case in JUnit to test the behaviour / expected results of 2 threads. I'm looking for feedback for this code. In ...
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Turn a non-blocking concurrent queue into a blocking concurrent queue
Microsoft Visual Studio offers a non-blocking concurrent queue class, concurrency::concurrent_queue, based on Intel's TBB. I am using this as a base for a blocking ...
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Concurrent Stack with blocking and non-blocking methods
I wrote it this just for learning. Is there holes at this code?
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Concurrent blocking stack
I just want to train before interview. I googled concurrency interview questions and one of the question was write concurrent ready stack.
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Running multiple producer and single consumer in a multithread environment
I have a below class in which add method will be called by multiple threads to populate messageByChannelReference concurrent ...
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Parallel brute-force solution for Project Euler 4 (Largest palindrome product)
The pe4Concurrent.go file given below is my first attempt at writing a concurrent programme, pe4.go is a non-concurrent implementation of the same algorithm for comparison purposes.
The algorithm ...
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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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Receiving messages from TCP socket and processing them
I would like someone to look at my class for reading messages from a network socket. In short, the whole app should behave like a regular ping command with some additional functionalities. The point ...
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