Quaternion
SPSCQueue.h
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Quaternion | SPSCQueue.h | |
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3 | 1 | |
627 | 825 | |
2.1% | - | |
8.7 | 4.6 | |
2 months ago | 4 months ago | |
C++ | C++ | |
GNU General Public License v3.0 only | MIT License |
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Quaternion
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OpenSUSE Linux Gains Momentum: A Look at Its Growing Popularity
> Meanwhile there have been exactly zero new F/OSS desktop apps for over a decade except IDEs and even those are mostly Electron-based. What a mess.
Er, that's just objectively not true. Here's exactly one new FOSS desktop app: https://github.com/quotient-im/Quaternion - I don't know how old it is, but it's a Matrix client and Matrix is only 8 years old so less than a decade.
- Haiku R1/beta4 has been released
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Notes on Concurrency Bugs
In terms of shared-memory threading concurrency, Send and Sync, and the distinction between &T and &Mutex and &mut T, were a revelation when I first learned them. It was a principled approach to shared-memory threading, with Send/Sync banning nearly all of the confusing and buggy entangled-state codebases I've seen and continue to see in C++ (much to my frustration and exasperation), and &Mutex providing a cleaner alternative design (there's an excellent article on its design at http://cliffle.com/blog/rust-mutexes/).
My favorite simple concurrent data structure is https://docs.rs/triple_buffer/latest/triple_buffer/struct.Tr.... It beautifully demonstrates how you can achieve principled shared mutability, by defining two "handle" types (living on different threads), each carrying thread-local state (not TLS) and a pointer to shared memory, and only allowing each handle to access shared memory in a particular way. This statically prevents one thread from calling a method intended to run on another thread, or accessing fields local to another thread (since the methods and fields now live on the other handle). It also demonstrates the complexity of reasoning about lock-free algorithms (https://github.com/HadrienG2/triple-buffer/issues/14).
I suppose &/&mut is also a safeguard against event-loop and reentrancy bugs (like https://github.com/quotient-im/Quaternion/issues/702). I don't think Rust solves the general problem of preventing deadlocks within and between processes (which often cross organizational boundaries between projects and distinct codebases, with no clear contract on allowed behavior and which party in a deadlock is at fault), and non-atomicity between processes on a single machine (see my PipeWire criticism at https://news.ycombinator.com/item?id=31519951). File saving is also difficult (https://danluu.com/file-consistency/), though I find that fsync-then-rename works well enough if you don't need to preserve metadata or write through file (not folder) symlinks.
SPSCQueue.h
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Notes on Concurrency Bugs
A triple buffer is a good choice if all you want is polling the latest data at any given time, and you want to avoid mutexes altogether. If you want each piece of data to be delivered exactly once, you can use a queue (bounded or "unlimited" though the latter doesn't supply backpressure which I hear causes problems). SPSC lock-free bounded queues are dead simple to write, and can be tuned for higher throughput even with contention (https://github.com/rigtorp/SPSCQueue claims to be nice, and I haven't had issues working with it aside from having to peek and pop separately, but it's C++, and not a misuse-proof API since it doesn't use the "handles" idea I talked about, and you can push/read/pop from the wrong thread). If you want the reader to poll/WaitForMultipleObjects until the queue has items, that has to be done separately from the SPSC.
And mutexes make a lot of things easier... and introduces "oops wrong mutex!" (Rust solves it) and deadlock (Rust doesn't solve it).
What are some alternatives?
diffractsim - ✨ A flexible diffraction simulator for exploring and visualizing physical optics.
moodycamel - A fast multi-producer, multi-consumer lock-free concurrent queue for C++11
fdtd - A 3D electromagnetic FDTD simulator written in Python with optional GPU support
HPX - The C++ Standard Library for Parallelism and Concurrency
haiku - The Haiku operating system. (Pull requests will be ignored; patches may be sent to https://review.haiku-os.org).
libdill - Structured concurrency in C
pgadmin3 - PgAdmin3 с поддержкой PostgreSQL 16
VexCL - VexCL is a C++ vector expression template library for OpenCL/CUDA/OpenMP
clientpp - Krunker client written in C++ and powered by WebView2
Taskflow - A General-purpose Parallel and Heterogeneous Task Programming System
triple-buffer - Implementation of triple buffering in Rust
libcds - A C++ library of Concurrent Data Structures