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 ...
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19 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
55 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
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0answers
25 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
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0answers
33 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
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1answer
46 views
Golang: reading and processing a big csv file
I am quite new to Golang. I am trying to write a script to read a CSV file containing 1 million domain names, lookup these domain names and store the results in another CSV file. I am trying the ...
3
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0answers
38 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 ...
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0answers
38 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
65 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 ...
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1answer
36 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:
...
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1answer
107 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
166 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
49 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.
...
0
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1answer
52 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
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2answers
30 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
8 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
77 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
46 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
28 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
43 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
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1answer
126 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
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0answers
28 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
111 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
34 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
136 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
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1answer
38 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
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0answers
45 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
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1answer
80 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
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2answers
132 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
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0answers
66 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
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1answer
89 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
3answers
46 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
61 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
214 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
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1answer
85 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
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0answers
56 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
81 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
606 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
643 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
104 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
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0answers
53 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 ...
0
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0answers
56 views
Having critical section for PHP using redis
Currently, I'm using redis to implement critical section for PHP code, to ensure there isn't more than one process/thread to execute the enclosed code block. I was wondering, is there any edge cases ...
4
votes
1answer
51 views
OutputStream class for use with subprocess.Popen
I've recently been writing an application which does a lot of work with the output of commands. To call the commands I've been using the subprocess module, and originally, was using ...
2
votes
1answer
61 views
Java “pulse” between threads
I have two threads. One runs a simulation and one runs a UI.
In the UI, it is possible to trigger a "tick" of the simulation. There are a few constraints:
Ticks run on the simulation thread
Each ...
4
votes
0answers
37 views
Baby Step Giant Step Discrete Log Solver
I've made a concurrent implementation of the Big Step Giant Step discrete log solver in Go. I'm pretty new to this branch of math, but it seems slow. Any way to speed it up or is this the limit of ...
3
votes
1answer
83 views
Parallel scheduler for running actions at designated times
I've been trying to learn Haskell on and off for a couple years. I had a project for building a parallel web scraper, and I figured I'd try to use Haskell for it. Here's the part used to schedule ...
6
votes
1answer
43 views
Class managing queuing updates from another thread, Version 2
This is an updated version of: Class to manage updates coming in from another thread
Managing updates from other threads into Swing is a hard problem. In MVC design, if you don't want to have the ...
1
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0answers
64 views
Batching using semaphores
I need to batch messages when pushing them, where multiple threads do the publishing. What could be a better way of doing this?
...
5
votes
2answers
63 views
Class to manage updates coming in from another thread
Managing updates from other threads into Swing is a hard problem. In MVC design, if you don't want to have the Presenter be responsible for Thread safety, you can end up with deadlock issues, and also ...
5
votes
1answer
87 views
Multi-threaded bitcoin vanity address generator written in Java
The application leverages the bitcoinj library to generate a vanity bitcoin address. A vanity address is simply a bitcoin address that contains a personalized string. I would like some critical ...
1
vote
1answer
72 views
ArrayBlockingQueue - blocking drainTo() method
This is a follow-up question to this question.
Is this a reasonable implementation for a blocking version of method ArrayBlockingQueue.drainTo(Collection)?
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