Multi-threading related questions including technique, structure, and safety issues.

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2
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3answers
154 views

Concurrent collections, should read methods allow multiple threads at one time?

I have custom collection and I want to add wrapper to allow concurrent access. public class MyConcurrentCollection<T> { private MyCollection _collection; // passed in constructor ...
3
votes
4answers
3k views

Can multiple CPU's / cores access the same RAM simutaneously?

This is what I guess would happen: If two cores tried to access the same address in RAM, one would have to wait for the other to access the RAM. The second time that each core would try to access ...
-1
votes
1answer
29 views

What's the best way to implement a real time show board to show results from concurrent result producers in Java?

I'm making a load test tool that launches multiple thread to simulate load on the target server. Each thread executes a predefined set of commands in the structure of TestSuite - TestCase- TestStep ...
0
votes
2answers
46 views

Why should we expect user-space coroutines to be lighter than OS threads?

I have heard it said that managing concurrent TCP connections using user-space coroutines uses less resources per open connection than using an OS thread per connection. Actually, OS threads and ...
1
vote
0answers
29 views

Android: How to set a stop flag in native C thread from Java

In my NDK Android app, Java part runs native C code to perform intensive calculations. It does so by creating an AsyncTask worker object that runs the native code in a separate thread via the JNI. The ...
6
votes
2answers
9k views

How to program thread allocation on multicore processors?

I would like to experiment with threads on a multi-core processor, e.g. to create a program that uses two different threads that are executed by two different processor cores. However, it is not ...
2
votes
1answer
50 views

How many threads should I use in my NIO server, details inside

I've built a Java NIO TCP server, it currently uses four threads. One ServerRunnable thread that uses a selector and three worker threads. I've been looking around for some information about this, ...
2
votes
1answer
83 views

Strategies for handling or avoiding race conditions

I'm working on a .NET application where I off-load my DB work (save operations) to a separate thread (inspired by how NodeJS handles IO operations). A save operation comes down to this (using Entity ...
15
votes
8answers
19k views

Multithreading synchronization interview question: Find n words given m threads

I came across this question: You are given a paragraph , which contain n number of words, you are given m threads. What you need to do is , each thread should print one word and give the ...
1
vote
1answer
50 views

What are the underlying patterns in systems allowing asynchronous operations?

Say I'm working with a system that allows async, nonblocking operations. If I queue up a set of those operations and specify their result buffer references: nonblocking_write( message, write_buffer ...
0
votes
0answers
25 views

Why Waiting Thread Doesn't wait forever [migrated]

I found below code for replicating the join() behavior in Java. There are two possible execution path: When Main thread continues execution and enters into the synchronized block. It then has to ...
-1
votes
0answers
34 views

Using Process.Start to capture console output [migrated]

unfortunately i'm new in C# and this should be a stupid question but i need it, hope someone should help.. Based on this article: ...
0
votes
0answers
55 views

How is CancellationToken.IsCancellationRequested updated?

I've been doing some refactoring today and I encountered one interesting thing. I've extracted a method from a code which uses a cancellation token passed to it in order to check if the user did not ...
3
votes
2answers
115 views

Design, how to utilize The Hardware (multiple threads and/or GPU) while indexing (via a database) a very large set of binary files

Problem How can design my file parser to maximize the hardware when processing (creating meta data for) a large file (i.e. how to avoid being blocked by IO and running out of memory) preferably ...
3
votes
1answer
287 views

Scheduling a few CPU-intensive tasks

I need to schedule a small number of CPU-intensive tasks to run every so often, reading from shared data and writing to dedicated buffers. I don't necessarily want to roll my own scheduling, but am ...
4
votes
1answer
70 views

Should I implement the consumer/producer pattern in my java video app, and if yes, how?

I built a small video frame analysis app with desktop Java 8. On each frame, I extract data (5 doubles now, but could expand to a 1920x1080x3 OpenCV Mat in the future). I would like to store this data ...
0
votes
0answers
70 views

Java write to text file from multiple threads

I have a thread which read and insert new lines in same file. I must synchronized that file so that no other thread is not accessing the file at the same time. Here is how i will synchronize a file ...
4
votes
2answers
327 views

Const means Thread-safe?

I was put onto this video: http://channel9.msdn.com/posts/C-and-Beyond-2012-Herb-Sutter-You-dont-know-blank-and-blank By http://codereview.stackexchange.com/users/39810/glampert Because I asked ...
0
votes
1answer
49 views

Multithreading message broker in a transactional system - Best Practice [closed]

We have 2 systems that exchange tickets base on a transactional flow, they have an order in the ticket statuses if one status does not reach one system all the flow is stuck. The problem is that we ...
0
votes
0answers
20 views

How to run a function after returning 201 view [migrated]

I'm using the Django Python framework with the Django REST Framework. When a new instance of a model is saved, I need to generate a PDF that is saved locally on the server. Is there a way that I can ...
2
votes
1answer
114 views

How much physical memory is consumed by the stack of a .NET thread?

In Stephen Cleary's article in MSDN magazine "Introduction to Async/Await on ASP.NET" he says that "every thread pool thread on a modern OS has a 1MB stack." (modern OS == Windows 7/8 for this ...
3
votes
1answer
85 views

How is atomicity of reference operations enforced?

In managed languages how is atomicity of reference operations enforced? On some platforms references have to be at least 64 bit, so it cannot rely on usually atomic 32 bit word operations... Is it ...
7
votes
4answers
586 views

How to prevent others from using non-thread safe variables in a multithreading environment?

I have an application written in C++ that was originally single threaded, but, due to the increasing complexity of this project, I'll need to expand it to at least two or three threads. There are ...
3
votes
2answers
127 views

are multithreading, multiprocessing, multitasking implemented at instruction set or OS?

On a computer with a single cpu core, must a multithreading program be implemented based on an OS? Can it be implemented in the instruction set and run without an OS? Can multiple programs run in ...
0
votes
1answer
106 views

How shall I handle event loop exceptions?

What is the best practice for handling exceptions thrown from event handlers/listeners in a event loop? For example: class EventLoop { public: void start(); //create a thread which calls run(); ...
15
votes
3answers
10k views

UML Diagrams of Multi-Threaded Applications

For single-threaded applications I like to use class diagrams to get an overview of the architecture of that application. This type of diagram, however, hasn’t been very helpful when trying to ...
2
votes
1answer
72 views

Should a lockfree queue use a condition variable?

Suppose I have a lockfree queue in a multithreaded setting. I already provide a try_dequeue() method which allows for an optional failure (communicated via the return type) if the queue is empty. ...
1
vote
2answers
120 views

Why don't we see (more) widespread adoption of lock-free dynamic memory allocators? [closed]

In a multithreaded programming environment, lock contention on the heap is often enough a performance bottleneck. Theoretically at least, the cream-of-the-crop solution for this problem is to have ...
1
vote
0answers
77 views

Concurrent directory-tree search

I am trying to get familiar with concurrent programming, and have picked up an excercise to use a fixed number of threads that search through a directory structure. This is pretty much the way it is ...
0
votes
3answers
262 views

MVC pattern synchronisation

I am facing a problem in synchronizing my model and view threads I have a view which is table. In it, user can select a few rows. I update the view as soon as the user clicks on any row since I don't ...
1
vote
2answers
233 views

How does the consumer-producer solution work?

I'm only a beginner, and my book doesn't cover this subject. I have researched my problem and found that an implementation of the consumer-producer pattern is the ideal solution, and have Googled it, ...
4
votes
2answers
136 views

Why don't all UI Control methods RunOnUIThread

In both .NET and in Android and I'm sure other frameworks I've noticed this issue where you end up with a task that takes too long and so holds up the UI thread. Say you have a method that updates a ...
53
votes
12answers
8k views

Why would a program require a specific minimum number of CPU cores?

Is it possible to write code (or complete software, rather than a piece of code) that won't work properly when run on a CPU that has less than N number of cores? Without checking it explicitly and ...
1
vote
3answers
980 views

How to preserve order of incoming requests on a multithreaded server

I want to write a multithreaded server application which is able to process requests in a multithreaded fashion while keeping up execution order of incoming requests of the same client. For example ...
0
votes
1answer
103 views

Controlling concurrency by Thread Pool in scenario of CPU-intensive and I/O intensive requests?

My goal is to understand how to handle jobs coming from the client side at very high frequency each job is either CPU-intensive or I/O intensive, but both types of jobs are continuously arriving at my ...
17
votes
3answers
6k 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, ...
15
votes
1answer
3k 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 ...
5
votes
1answer
308 views

What is the advantage of 'SwingUtilities.invokeLater()' method?

For the below sample GUI program using javax.swing, public class UnResponsiveUI extends JFrame{ private boolean stop = false; private JTextField tfCount; private int count = 1; /* ...
1
vote
3answers
184 views

Is there an algorithm to determine the amount of work needed to keep workers busy?

I wrote a multi-threaded program that randomly generates strings, and after generating, checks to see if the string contains a certain value. Namely, StringGenerator and StringChecker. What I'm trying ...
7
votes
1answer
206 views

Message Queue for RTOS for microcontrollers

I'm currently writing an RTOS for microcontrollers. The whole thing is written in C++11 - if anyone is interested, and the link to the repository is at the bottom. Currently I'm writing a class that ...
1
vote
2answers
264 views

How to Keep Track of Thread Safe Code in a mostly Thread Unsafe Legacy Rich C++ Code Base

For large legacy C++ code bases, notions like Herb Sutter's "const means threadsafe" don't seem to help much, because there can be an overwhelming amount of code in const functions which are modifying ...
6
votes
3answers
318 views

Design solution for communicating between multiple layers

We are developing a framework that has several layers and would be deployed in a multi-threaded environment. Each layer may have its own input/output data type. The top layer takes the input, performs ...
2
votes
1answer
190 views

Most efficient/cleanest way to Kill a recursive thread safely

I have a number of worker threads which all perform a flood-fill task on different regions of a bitmap. They all make calls to a recursive sub-routine with different parameters(coordinates). Fyi, I am ...
6
votes
2answers
655 views

Does laziness yield more race conditions?

I recently ran into a race condition while accessing a configuration setting. After examining what I could of the code, I came to the conclusion that the Configuration class' laziness1 was the source ...
1
vote
2answers
261 views

Should CountDownLatch be used for waiting for an event?

I have a situation here, where I have a loop that loops x amount of times. The value x is determined by the user. Everytime it loops, I want it to wait for a button click before continuing the loop. ...
2
votes
1answer
73 views

Can concurrent code (threads, distributed computing, etc.) be directly ported to single-threaded/non-networked platforms?

Take an arbitrary "perfect" multi-threaded program, on an arbitrary multi-threaded platform, using an arbitrary programming language. Assuming that this "perfect" multi-threaded program: is ...
-2
votes
2answers
146 views

Using a global struct with pthreads in C [closed]

I'm trying to simulate clients going into a bank and being served by tellers over a period of time. I am using a thread to determine if a client came into the bank via an arrival rate and am using ...
1
vote
1answer
147 views

Synchronized access to network industrial equipment

I have an industrial equipment which is controlled by a software. The software connects to it using sockets, and keeps the connection all the time alive, while from time to time sending commands to ...
3
votes
1answer
121 views

Seeking Guidance on Thread Safe Scripting

I am trying to write a script that will take multiple paths to files on various servers, search them all simultaneously, and return a single list of results to a user. Initially, I was just using ...
3
votes
0answers
48 views

Evaluating concurrent application design approaches on Linux

Working on relatively low-speed hardware, I need to grab a snapshot of a rapidly changing datastream and then post-process the snapshot data and save it to disk. I need help with designing the ...