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 ...
3
votes
0answers
12 views
Java controller to farm out concurrent tasks
I've recently given a coding interview on a Java concurrency task and unfortunately didn't get the job. The worst part is I've given my best but now I'm not even sure where went wrong. Can anyone ...
5
votes
1answer
140 views
Concurrent for loop in C++
I have this easy to use facility that maps input elements to output elements concurrently by the means of a thread pool:
concurrent.h:
...
4
votes
4answers
111 views
Implemenation for concurrent file access (read/write)
I am developing an application that works with files and folder on a network share (similar to the windows explorer). The application is used by multiple users and provides some commands for modifying ...
1
vote
1answer
50 views
Multithreaded Producer-Consumer pattern
I have Producer Threads A, B and C producing 3 different types of events Events A, B and C respectively. The Consumer thread can ...
2
votes
1answer
38 views
Managing PostgreSQL transactions for concurrency
I have a situation where I need to use PostgreSQL's serializable isolation level for transactions. This is for a table shared among multiple concurrent PHP processes. If the database runs into any ...
8
votes
1answer
101 views
Naive parallel Sieve of Eratosthenes in Java
My naive version now is too slow. I think setting/accessing concurrent atomic bit is way slower compared to access/modify an array of boolean. Second, the parallel execution only happens on the ...
0
votes
0answers
72 views
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 ...
3
votes
1answer
102 views
Concurrent non-blocking update of cached list of on-line users
I have following problem: My server (ASP.MVC WebAPI) is tracking, when client application ("Agent") is on-line. It's storing this inf on following table:
...
-2
votes
1answer
24 views
Capture some state in Haskell
I want to capture some state in a Haskell function. For instance, I have many thread trying to print on the console and I want the to play nice with each other. So I want to have some XX to make the ...
2
votes
3answers
85 views
C++11 Blocking Queue learning exercise
As part of my own C++11 learning exercise I have implemented this Blocking Queue using the new C++11 thread API. One of the aspects I would like to improve is efficiency i.e. in the ...
1
vote
0answers
37 views
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.
...
4
votes
0answers
72 views
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 dfs on it.
How can I make the ...
3
votes
1answer
64 views
Reader-writers problem using semaphores in Java
I have written my own solution to the Reader-Writers problems using semaphores based on the psuedocode from Wikipedia. I would like to gauge the correctness and quality of the code.
...
2
votes
0answers
53 views
Concurrent resizable ring buffer Golang
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
(...
1
vote
1answer
118 views
Reading and processing a big CSV file
I am trying to write a script to read a CSV file containing 1 million domain names, look up these domain names and store the results in another CSV file. I am trying the following code, but the number ...
3
votes
0answers
62 views
Golang Tour Web Crawler Exercise
In the last few days I've played around with Go a little and took the language tour. The last exercise (text here) requires you to crawl a graph that simulates a set of Web pages with links, using ...
4
votes
1answer
56 views
Multiple Persons enter room simultaneously and exits after specific interval of time
Here is the link to git repo of my application I am currently implementing just to have better understanding of OOP as well as learning Concurrency (Atleast a try :D)
What is the whole ...
4
votes
2answers
88 views
Go lang Tour Webcrawler Exercise - Solution
I am new in Go and for study I have to hold a presentation about concurrency in Go. I think the Go lang Tour - Webcrawler exercise is a nice example to talk about that. Before I will do that, it would ...
0
votes
1answer
61 views
Design of thread pool reuse with Executors.newFixedThreadPool in Java
In my application I have code which should run every hour on a new items and execute some expensive operation with multithreading:
...
1
vote
1answer
147 views
Thread safe REST API
My assignment was to develop a REST service that will provide Airport information. This service is assumed to be used by multiple users, therefore data consistency (thread safety) and responding fast ...
2
votes
1answer
170 views
A very basic semaphore in Java
Here is is a fixed code, taking in to account Spurious wakeup issue.Thanks to Costa for bringing that up.
ISemaphore:
...
3
votes
1answer
52 views
A scalable lock-free channel
Here's my lock-free channel impl lfchan,
I didn't want to copy/paste the code here since it is multiple files.
I'm trying to get an idea of what can be improved or if there are any bugs in it.
chan....
0
votes
1answer
67 views
Processing files retrieved through FTP in parallel
I am busy creating a file processor that needs to get some files from an Ftp client download the file and save the data into the database. I have a two part question.
How can i refactor the code to ...
0
votes
2answers
32 views
Initialization lock for singleton
I'd like someone to double-check my use of Atomic primitives, because multi-threading is hard.
What I don't want to do is locking the whole get method, or having too many pre-checks per get() call.
<...
0
votes
0answers
9 views
Robustly send notifications from multiple processes
We have Notifications stored in a notifications table, which is worked on by multiple background workers. The notifications table has these relevant attributes:
id (primary key, unique)
send_at (...
6
votes
1answer
80 views
Can my cache be more thread safe?
I have been working on a cache that can handle multiple reads at the same time, but the write is blocking.
Is this code overkill by using both a ConcurrentHashMap ...
4
votes
1answer
47 views
Reporting the status of the actions of a group of SKSpriteNodes
Working on a little Sprite Kit game, I had the problem that I wanted a couple of things to wait until a group of sprite nodes had stopped their animation.
I decided to use a GCD dispatch group to ...
2
votes
1answer
29 views
Distributed (asynchronous) averaging
This code simulates a distributed averaging protocol. There is a network of nodes, and at the clicks of a Poisson process:
A random node wakes up
Transmits it's current average to all the nodes it ...
0
votes
1answer
45 views
Tree processing for series and parallel execution
I have a tree processing application where some of the nodes are "executed" in parallel and some in series. I managed to do this but I feel that the solution looks a bit "hacked up" and can be ...
1
vote
1answer
272 views
Executor Service with Blocking Queue
I did not find a single working implementation of using an Executor Service with a Blocking Queue. So , I have come with with a working sample. Thoughts?
...
2
votes
0answers
30 views
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
...
2
votes
1answer
240 views
Parallel Task Queue that runs in sequence
I'm in need of a solution that runs constantly incoming requests in a per-resource sequence, but parallel in general.
The use-case:
Many clients connect to a server and start issuing work. The work ...
1
vote
0answers
35 views
Purging elements from the map if it reaches a memory size limit
I have implemented a LRU cache using ConcurrentLinkedHashMap. In the same map, I am purging events if my map reaches a particular limit as shown below.
I have a ...
5
votes
3answers
176 views
Simple Java task scheduler
The task is pretty simple: implement a timer that executes tasks when the next event takes place. I created a task scheduler based on a priority queue.
A new thread is created for ...
7
votes
1answer
39 views
Refactoring a phantom server called Swayzee
I have made a tool that is pretty useful for me. I have made it open source on github. It is a server that listens for requests and returns an HTML static version of a single page app. It works with a ...
3
votes
0answers
47 views
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, ...
2
votes
1answer
104 views
Unfair semaphore in Java
I'm tutor for a university operating systems course, and part of my work is creating exercises for them. Those exercises are mostly about concurrency and synchronization issues. For the next exercise ...
4
votes
2answers
161 views
Parallel foreach with configurable level of concurrency
The purpose of this code is to let me loop over 100 items (up to MAX_CONCURRENT at a time), performing some action on them, and then return only once all items have ...
0
votes
0answers
81 views
RabbitMQ RPC client
I'm familiarising myself with RabbitMQ and Clojure, so I looked at the Get Started guide for the former and added the client and server parts for the RPC tutorial.
I already got the feedback that ...
10
votes
1answer
95 views
ConcurrentDecayingHashMap<K,V>, a concurrent decaying HashMap
I wrote a wrapper for Java's ConcurrentHashMap that enables you to add a decay time to inserted values, meaning they will be automatically removed after the given ...
3
votes
2answers
47 views
Visualize the runtimes of list algorithms
I wrote a small script to visualize the runtimes of list algorithms.
The script works by creating a list of lists with sampled lengths from 1 to max_size. Next, I ...
5
votes
1answer
62 views
Lock implementation using atomics
I was recently given an interview and was asked to write my own lock implementation using atomics, but not necessary reentrant.
I didn't answer the question, but at home, I wrote this code. Please ...
10
votes
1answer
226 views
“Barbershop”-esque Semaphore Implementation
Recently, I submitted a project that simulates a barbershop-style problem; the task was to create a Hotel that contained guests, front-desk employees, and bellhops. ...
7
votes
1answer
92 views
Fast non-fair semaphore
This is a simple non-fair semaphore implementation using Java atomic objects. It currently performs a little over twice as fast as java.util.concurrent.Semaphore on ...
1
vote
0answers
57 views
Self cancelling period tasks
I've got a piece of code that will run a period task to do a small bit of processing. The task depends on an externally managed connection resource, and if the resource goes away then the task should ...
0
votes
3answers
91 views
Implementing multiple Producer Consumer using custom Blocking queue [closed]
I am trying to implement multiple producer multiple consumer problem using a custom blocking queue. The requirement is that:
If the queue is not full, all the producers should be able to produce ...
6
votes
1answer
939 views
Printing even and odd using two concurrent threads
Please review the code below where thread Odd prints all odd numbers from 1 to 9 and thread Even prints all even numbers from 2 to 8. I tested it and it works but can we improve it from design or ...
4
votes
1answer
926 views
Canonical Implementation for a Concurrent Subclass of NSOperation in Swift 2
I would like to develop a kind of template or canonical implementation for a concurrent subclass of NSOperation in Swift.
See here for my previous request which is implemented in Objective-C.
In that ...
3
votes
3answers
112 views
SPSC Wait Free Ring Buffer for incoming messages
This is for a single producer and single consumer wait free ring buffer. The writes need to be wait free for sure. It pre-allocates messages slots and uses a claim strategy to capture a buffer for ...
0
votes
0answers
55 views
SQLite app for local storage
When I make an app using SQLite for local storage I've settled into a nice routine; create a contract class and a extended BaseColumns class to hold column names ...
