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.
370
questions
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Why gRPC does not consume all of the threads and gets timed out? [closed]
As I have read from this link about max_workers and maximum_concurrent_rpcs. It is seems that when I set max_workers to 1 and ...
9
votes
4answers
2k views
AsyncDictionary - Can you break thread safety?
This class is an Async/Await wrapped Dictionary. Of course it doesn't technically implement IDictionary, but the functionality is basically the same as an IDictionary. It achieves similar ...
4
votes
2answers
376 views
Unisex Bathroom problem without semaphore
Could I ask you to evaluate my solution to Unisex Bathroom Problem?
Problem description
An office has a bathroom that can be used by both men and women, but not both at the same time. If a man is ...
2
votes
1answer
80 views
Find shortest path in the matrix for multiple objects
I have the implementation of A* search algorithm that allows to find the shortest path from start to goal.
The implementation looks like this
...
5
votes
2answers
148 views
Async concurrency prevention class
Because I'm quite naive regarding C#'s Task Asynchronous Programming and concurrency in general, and because it's so difficult to test, I'm concerned about the safety of this code. It's likely that ...
6
votes
0answers
38 views
Concurrent Queue Adapter
There's lots of code out there for basic adapters of std::deque to provide a thread-safe queue. I've adopted that, but wanted to provide a relatively full analog to ...
11
votes
2answers
505 views
Parallelized for loop in Bash
I am using a Bash script to execute a Python script multiple times. In order to speed up the execution, I would like to execute these (independent) processes in parallel. The code below does so:
<...
3
votes
1answer
119 views
Determine concurrent access to a function
Someone asked here how to determine a function is being called from multiple threads. My take on this is that they are asking about concurrent access not sequential access. The accepted answer ...
2
votes
1answer
33 views
Performing an action which may return other actions to be performed, concurrently
I have a program which, at its core, involves repeatedly performing an action on some value, and based on that action also returning a list of new values to perform that action on. The pure version of ...
1
vote
0answers
23 views
Process 2 lists concurrently with the first list adding to the second [closed]
I'm new to multi-threading and concurrency. I've got 2 lists that I want to process concurrently. Processing both lists requires a lot of time.sleep() and waiting for other servers to finish, so I ...
1
vote
2answers
182 views
Multi-Threaded Cellular Automata Lab
I am trying to improve the performance of my cellular automata lab. I have two arrays of Doubles representing the current values and the next values.
If I run the ...
1
vote
0answers
20 views
Take a list of ascii strings from a file and hash them using python threading
How can I do this in a more performant way? I'm concerned that throwing the data in a queue like this is defeating the purpose of yield from the ...
2
votes
0answers
36 views
Comparing Java Semaphore versus ReentrantReadWriteLock
In this post, I attempted to compare the performance of two concurrency constructs:
java.util.concurrent.Semaphore,
...
2
votes
0answers
176 views
Many-readers-one-writer with semaphores and multithreading
I've been looking for a solution to the may readers one writer in Java.
I was intrigued by this question posted here and I read the Wikipedia entry about it.
So far, I've reached a fine solution, or ...
4
votes
0answers
380 views
Safely executing background tasks in parallel in ASP.NET Core
Context and initial idea
I'm trying to teach myself the CQRS and Event Sourcing patterns by developing a simple ASP.NET Core application, loosely following Greg Young's example CQRS implementation on ...
7
votes
1answer
95 views
Quiz game with timer
This is my first Go program. I would like to know what could be improved, what is done wrong, and anything else that I should know. The CSV contains 10 questions with the 10 answers separated by a ...
3
votes
2answers
78 views
Download and save bulk URL concurrently
I am new to Go and wrote program to download and save bulk URLs concurrently. It is working correctly, but I would like to make it more efficient and follow best practices.
...
3
votes
2answers
328 views
java Thread-safe LRUCache implementation
What is best way to implement thread-safe LRUCache in java?
Please review this one.
Is there any better approach which can be taken here?
...
0
votes
1answer
88 views
Finding the longest Collatz sequence using Go, concurrently
I am working through this problem on project euler.
Basic purpose of the code:
...
0
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0answers
35 views
Mutex implementation using Windows APC
I just wrote this now and didn't test it much. This isn't a replacement for std::mutex, but for something like fun. I may develop it to make it shared across processes by storing the counters in a ...
4
votes
1answer
109 views
Reader Writer SpinLock
I'm quite new to C++ and want to focus on writing performant multithreaded code because I will try to port our company internal GUI framework which is currently implemented in C#. So I'd love to get ...
0
votes
0answers
19 views
Dynamic “compilation” of SQL stored procedures
I have a stored procedure which is called to create ( "compile" ) temporary stored procedures, code below, based on whether a flag in a database record is set - the various sub-procedures such as ...
4
votes
2answers
64 views
Upload a directory, in parallel, to an artifact repository
This code uploads an entire directory and allows for its reparenting on a remote server (an artifact repository).
Three concerns:
Copying the files locally takes a lot of space. Ideally, I could use ...
1
vote
2answers
378 views
Golang execute several go routine in loop and then wait
I'm new in Go and excited with its easy-to-use concurrency implementation. However I'm not sure if I'm doing it right in Golang way.
Consider the code where I spawn ...
2
votes
1answer
50 views
Batch downloading to file or memory
This is likely my first useful piece of Rust code. Planning to crate-ify it. It works.
...
5
votes
2answers
112 views
Using two threads to increase RFC1951 Deflate compression performance
I have modified my implementation of RFC 1951 "Deflate" compression to use two threads. One thread performs the LZ77 matching, looking for sequences of at least three bytes that occur earlier in the ...
0
votes
0answers
21 views
Go wrapper around io.Writer that tracks the number of bytes written
The code below implements ProgressWriter, a wrapper around io.Writer that can track the number of bytes written, and a function <...
5
votes
2answers
93 views
Automatic RAII wrapper for concurrent access
Probably many people had to work with multithreaded applications with C++ and can understand how messy can be fine-grained locking of objects.
So once in a while I came to idea of implementing some ...
1
vote
0answers
64 views
Critical section around given key
I would like to know if there is any pre-existing implementation of my solution so I don't have to reinvent the wheel.
What I'm trying to create is an utility which allows me to create critical ...
0
votes
0answers
48 views
JNI: porting a semaphore data type to Windows
I have this JNI code to review. The demo driver + irrelevant porting code is here.
semaphore_impl.h:
...
2
votes
1answer
79 views
Reading shards from a Kinesis stream
Here is part of my implementation of reading a Kinesis stream. I am not confident that this is the best way to implement synchronizing returns from goroutine.
Assuming there are N shards in the ...
3
votes
2answers
296 views
Go grep command clone
I am trying to make a simple clone of the command line utility grep. I'm working on it just for fun and to practice Go. The thing is, I am trying to make it in a way that if several files are given at ...
4
votes
1answer
982 views
Concurrent observable collection
I'm working on a WPF 4.5 desktop application that has several nested collections with the following key aspects:
writes mainly from UI thread, but also from worker threads
writes are relatively ...
1
vote
0answers
376 views
Golang gRPC context to check if cancelled or if deadline is exceeded while running function code
I am writing a gRPC Golang application and am looking for the best way to check if the deadline is exceeded or if the client cancelled the call.
On the server side I created a channel called ...
3
votes
0answers
116 views
Linked list with hand-over-hand locking
Follow-up to this question: after reading the comments, I decided to redesign my linked list to have a cursor that only contains one node and implement the interface similar to the one of forward_list ...
5
votes
1answer
204 views
Specialized ConcurrentLinkedList
I need a concurrent data structure with the following properties:
Low overhead for enumeration
Insert only at end.
Removal from any point.
Enumeration should be safe with concurrent writing
...
0
votes
0answers
31 views
Running a JavaFX 11 interface update at regular intervals (in Kotlin)
I want to update a field on a JavaFX 11 UI in response to a thread which retries a process every second and updates statusString with the result. Since the ...
3
votes
0answers
60 views
Override prototype inside of constructor of ES6 class for dependency injection
We implemented a small dependency injection mechanism which we use in our project. Now after 2 years of developing our project we need our classes to know who instantiated them via dependency ...
1
vote
0answers
53 views
Using ReadWriteLock to implement a cache access guard
In my project, there is an internal cache api to use. I have noticed an emerging pattern such that:
...
3
votes
1answer
240 views
Rust Task Queue
The purpose of this program is to have one thread (main thread) working on I/O reading lines from a file and feeding it to a pool of worker threads whose job is to perform some processing on each line ...
2
votes
0answers
35 views
Comparing performance of multi- and single - thread search of a maximum number
I have a class that compares the performance of two methods (multi- and single- thread) that searches for maximum number in the string of numbers. I want to improve the performance of a multithreaded ...
1
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0answers
145 views
Thread-safe Java class for managing XML files <> domain models
This Java class (aka application component) role is to handle a series of XML files stored in the file system. It must convert those XML files to the corresponding application domain model, and it ...
7
votes
4answers
757 views
Caching Color-Bitmaps as MemoryStreams
I am in the need to cache Bitmap's in a memory-optimized way because the API I am building will need to process many colored ...
1
vote
1answer
116 views
Concurrent usage of resources
Please take a look at the following code. This is my attempt at understanding concurrent applications.
...
2
votes
1answer
225 views
Run two computations in parallel, and return the results together
I am reading the "Learning Concurrent Programming in Scala" and there are exercises in the end of each chapter.
One of exercises is
Implement a parallel method which takes two computation blocks a ...
2
votes
1answer
43 views
ProcessPoolExecutor KMZ file search
I've written a script to look for coordinates in KMZ files. I've tried to speed execution up using the ProcessPoolExecutor. I'm quite new to Python, so any recommendations are more than welcome.
<...
0
votes
1answer
42 views
Reading a user credentials from file concurrently [closed]
I came across the following code snippet:
...
5
votes
0answers
419 views
Custom TaskScheduler: Limited concurrency level [closed]
I'm interested in some feedback for a custom TaskScheduler implementation I wrote today for use on a game server - I wanted to be able to have a single-threaded ...
5
votes
2answers
2k views
ForEachAsync extension method (a way to run an async operation on each item of a sequence in parallel)
In a recent project I worked on we faced some issues due to an excess of parallelization (thousands of threads were created and the overall result was a degradation of performance and several spikes ...
3
votes
1answer
85 views
FutureTaskWrapper for Java
I did not like that get synchronizes every time I call it - because I may be calling it more than once. So I wrote the wrapper for the future interface which keeps ...
