Concurrency is a property of systems in which several processes are executing at the same time.

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How do you solve issue of consistency in concurrent and distributed application (built around Bankers Dilemma)?

This is a classic problem which I'm sure has been solved many times by many different people. I don't have any formal training (I've not studied computer science or any other such academic subject) ...
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1answer
62 views

Coordinating a complicated data migration process

A project I'm involved in has suffered a change in scope, and before I set about trying to cook up some homegrown solution, I'm wondering if there is something out there -- some framework, for example ...
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1answer
37 views

Patterns for creating adaptive web crawler throttling

Im running a service that crawls many websites daily. The crawlers are run as jobs processed by a bunch of independent background worker processes, that picks up the jobs as they get enqueued. Now ...
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0answers
29 views

Semaphore : one for each shared resource?

Normally semaphores are implemented as integer variables. The value of a semaphore represents initially the number of processes that are allowed to access the shared resource at the same time, which ...
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1answer
47 views

Repurpose MySQL as a mutex

My application needs to perform an operation once every 10 minutes, but that operation is triggered many times more frequently. Occasionally it is triggered three or four times a second in different ...
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1answer
152 views

Error Handling Strategies in Multithreaded Environments

TL;DR What error generating and handling strategies do you use in Multithreaded code intended for use by others and why do you use them? If applicable, state what programming paradigm it's useful for. ...
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1answer
1k views

Is there a difference between fibers, coroutines and green threads and if that is so what is it?

Today I was reading several articles on the Internet about fibers, coroutines and green threads, and it seems like these concepts have very much in common, but there are slight differences, especially ...
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1answer
113 views

In C++, are acquire-release memory order semantics transitive?

According to cppreference, we can use release-acquire semantics to ensure write-read precedence between two threads as follows: // Thread A 1. Write to X 2. Atomic store to Y with ...
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1answer
66 views

Implementing distributed Semaphore for AWS workload

We have a messaging gateway in AWS (Amazon Cloud) that comprises of a number of nodes (Linux servers) responsible for receiving, routing, despatching and escalating messages (emails, SMS' and voice ...
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1answer
41 views

handling online payment for items with one quantity - design issue

I would like to implement a robust way to handle ecommerce payment for items with limited quantity, like for example exclusive paintings. Payment would ideally be accepted via PayPal and credit ...
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1answer
82 views

Locking database records

What I have right now: A table with lot of records. About 200 users can select a record according to some rules based on the data in each record. There is a high chance that 2 or more users will ...
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4answers
2k views

What prevents a race condition on a lock?

I understand the basics of what data races are, and how locks/mutexes/semaphores help prevent them. But what happens if you have a "race condition" on the lock itself? For example, two different ...
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1answer
126 views

How to avoid oscillation by async event based systems?

Imagine a system where there are data sources which need to be kept in sync. A simple example is model - view data binding by MVC. Now I intend to describe these kind of systems with data sources and ...
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0answers
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How can I make a universal construction more efficient?

A "universal construction" is a wrapper class for a sequential object that enables it to be linearized (a strong consistency condition for concurrent objects). For instance, here's an adapted ...
2
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1answer
156 views

Where to implement thread-safety logic for my queue data structure?

I will immediately confess that I do very little multithreading, so questions of style and organization in this domain a little fresh to me. I've written a data structure (in Python, if that matters) ...
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0answers
17 views

Is Resque appropriate for an evented application?

As the title says, is Resque appropriate for an evented application that requires a decent amount of speed? I'm working on a server application that emulates the default Minecraft server, and I was ...
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1answer
155 views

Can the possibility of a data race be ignored in some cases? (while having concurrent threads) [duplicate]

I am programming a game engine as a hobby project, and I would like to separate physics and drawing into two separate threads. The position vectors of entities are subject to modifications by the ...
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0answers
56 views

Cache concurrency: ensuring latest version in cache

We have a data service app working on object graphs. We place some complex graphs in a (memory) caching tier as a single data item, so as to avoid the length of time to retrieve every individual data ...
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2answers
234 views

Are all race conditions worth fixing? [closed]

I just wrote the following piece of code (in delphi): procedure Update(Value: Integer); begin // If the last update was yesterday, replace yesterday value if CompareDate(FLastUpdate,Now) <> ...
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4answers
3k views

Programs that claim they are not “multi-core” friendly

You see this phrase or similar kicked around from time to time, generally referring to a program that claims they were not designed to take full advantage of multi-core processors. This is common ...
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3answers
915 views

Super Fast File Storage Engine

I basically have one big gigantic table (about 1.000.000.000.000 records) in a database with these fields: id, block_id, record id is unique, block_id is not unique, it contains about 10k (max) ...
12
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1answer
256 views

What intermediate representations can be used to reason about concurrency?

I am trying to better understand what would be required for a compiler to be able to make intelligent choices regarding concurrency on behalf of the programmer. I realize that there are many difficult ...
9
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1answer
2k views

Are go-langs goroutine pools just green threads?

The commentator here offers the following criticism of green threads: I was initially sold on the N:M model as a means of having event driven programming without the callback hell. You can write ...
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3answers
171 views

If mutual exclusion is not implemented, how would we detect a race condition?

Suppose we are in a distributed environment, and mutual exclusion is not implemented yet. So how would we be able to detect race conditions? When I researched, use of non-blocking algorithms was ...
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1answer
173 views

Does Clojure borrow concurrency ideas from Haskell?

In code quarterly interview with Rich Hickey Michael Fogus hints that Clojure borrows a lot from Haskell: Fogus: As someone who only knows Haskell enough to read the papers, Clojure appears to be ...
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1answer
236 views

Editing files without race conditions?

I have a CSV file that needs to be edited by multiple processes at the same time. My question is, how can I do this without introducing race conditions? It's easy to write to the end of the file ...
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2answers
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SQLite with two python processes accessing it: one reading, one writing

I'm developing a small system with two components: one polls data from an internet resource and translates it into sql data to persist it locally; the second one reads that sql data from the local ...
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1k views

Is The Free Lunch Over? [closed]

In his famous The Free Lunch Is Over article from 2005, Herb Sutter predicted a Concurrent Programming Revolution as big as Object-Oriented Revolution. Has this revolution really happend in years 2005 ...
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1answer
337 views

What do goroutines, Ruby Fibers, etc. look like to the OS/Kernel?

In process concurrency and thread concurrency it's quite obvious how the kernel sees these as they map directly to real things that the kernel manages. When it comes to Golang goroutines and Ruby ...
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1answer
188 views

How do I find a good middle way to make this library safe for concurrent operations

I've made a little library called SignalR.EventAggregatorProxy Before I push it into 1.0 state I need to fix so it works safely with concurrent operations. Easiest way is lock all operations but ...
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1answer
299 views

Apple Dispatch Queue vs Threads

I've heard a lot about apple's famous dispatch queues and the GCD but today was the first time I decided to understand exactly what is going on, so I started reading Concurrency Programming Guide and ...
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1answer
239 views

Handling or preventing conflicts in a multi-user system

I have a web application that is accessed by multiple users from different locations worldwide. Let's say I have an "edit" form for a specific document and two (or more) users are editing the document ...
8
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1answer
2k views

Erlang and Go concurrent programming, objective differences between CSP and Actors?

I was looking into concurrent programming in Erlang and Go programming languages. As per my finding they are used Actor model and CSP respectively. But still I am confused with what are the objective ...
6
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1answer
399 views

Which parallel pattern to use?

I need to write a server application that fetches mails from different mail servers/mailboxes and then needs to process/analyze these mails. Traditionally, I would do this multi-threaded, launching a ...
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3answers
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How many threads should access the file system at the same time?

We have a module in an application which stores data in multiple files and multilevel directories and access them from multiple threads (both reads and writes). The directory structure is based on a ...
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743 views

Uses of persistent data structures in non-functional languages

Languages that are purely functional or near-purely functional benefit from persistent data structures because they are immutable and fit well with the stateless style of functional programming. But ...
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2answers
751 views

Would Task-based programming in C++ require new language standard features?

So I saw this video on Youtube with all these C++ masters on GoingNative 2012 : Interactive panel where everybody could ask the questions. This is the video I was talking about: GoingNative 2012 - ...
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1answer
310 views

How can I benchmark concurrent key-value stores?

I have some concurrent key-value store implementations that are implemented with hash tables and search trees that I would like to compare. I would like to benchmark them with a real world application ...
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4answers
1k views

Functional Programming: right ideas about concurrency and state?

FP proponents have claimed that concurrency is easy because their paradigm avoids mutable state. I don't get it. Imagine we're creating a multiplayer dungeon crawl (a roguelike) using FP where we ...
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3answers
514 views

Multiple threads and single output source

For the sake of an exercise, say you have an input file with a series of lines of text with the objective of reversing their respective character sequences. Now introduce 5 threads that will each do ...
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4answers
7k views

The difference between “concurrent” and “parallel” execution?

What is the difference between the terms concurrent and parallel execution? I've never quite been able to grasp the distinction. The tag defines concurrency as a manner of running two processes ...
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181 views

How bad would it be to obtain a lock on every object?

Imagine a hypothetical programming environment that is largely like Java or .NET, i.e. object-oriented, garbage-collected, etc., but with one small change: Every time you call a method on an object, ...
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1k views

Why five dining philosophers?

I was wondering why the Dining philosophers problem is based on a five philosophers case. Why not four? I guess that we can observe all unpleasant issues that can occur when discussing five ...
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2answers
379 views

What is a good script language for writing server administration tasks? [closed]

I am administering hundreds of RHEL servers. There are many daily tasks to perform. Right now I am working with bash scripting and python. I was wondering if other languages such as Erlang, Lua, Ruby, ...
7
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1answer
393 views

In what meaningful ways does Erlang prevent race conditions in concurrent programming?

Reading about concurrency in Erlang, reminds me of the Akka concurrency toolkit. Both give you tools to prevent or limit race conditions. But you can send links to mutable data to other processes ...
5
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1answer
978 views

Common Lisp Implementations - threading and multiplatform?

I'm learning Common Lisp, mostly as a "mind gym" hobby thing, but I want to end up with a set of skills that would also be usable "in real life", because when you learn a language you also accumulate ...
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1answer
127 views

Design question about a concurrent forking server

I'm in the early stages of designing a client/server application. The clients will be batch programs that read a file of customer contact data (name, address, email address, phone no's) and pass ...
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3answers
4k views

Why is multithreading often preferred for improving performance?

I have a question, it's about why programmers seems to love concurrency and multi-threaded programs in general. I'm considering 2 main approaches here: an async approach basically based on signals, ...
11
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2answers
4k views

Are these advanced/unfair interview questions regarding Java concurrency? [closed]

Here are some questions I've recently asked interviewees who say they know Java concurrency: Explain the hazard of "memory visibility" - the way the JVM can reorder certain operations on variables ...
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1answer
256 views

Concurrency checking with Last Change Time

I have an app with the following three tables Email (emailNumber, Address) Recipients (reportNumber, emailNumber, lastChangeTime, status) Report (reportNumber, reportName) I have a C# application ...