Constvector: Log-structured std:vector alternative – 30-40% faster push/pop

Usually std::vector starts with 'N' capacity and grows to '2 * N' capacity once its size crosses X; at that time, we also copy the data from the old array to the new array. That has few problems

1. Copy cost,
2. OS needs to manage the small capacity array (size N) that's freed by the application.
3. L1 and L2 cache need to invalidate the array items, since the array moved to new location, and CPU need to fetch to L1/L2 since it's new data for CPU, but in reality it's not.

std::vector's reallocations and recopies are amortised O(1), but at low level they have lot of negative impact. Here's a log-structured alternative (constvector) with power-of-2 blocks: Push: 3.5 ns/op (vs 5 ns std::vector) Pop: 3.4 ns/op (vs 5.3 ns) Index: minor slowdown (3.8 vs 3.4 ns) Strict worst-case O(1), Θ(N) space trade-off, only log(N) extra compared to std::vector.

It reduces internal memory fragmentation. It won't invalidate L1, L2 cache without modifications, hence improving performance: In the github I benchmarked for 1K to 1B size vectors and this consistently improved showed better performance for push and pop operations.
 
Github: https://github.com/tendulkar/constvector

Youtube: https://youtu.be/ledS08GkD40

Practically we can use 64 size for meta array (for the log(N)) as extra space. I implemented the bare vector operations to compare, since the actual std::vector implementations have a lot of iterator validation code, causing the extra overhead.

https://redd.it/1ps8k53
@r_cpp

Crunch: A Message Definition and Serialization Tool Written in Modern C++
https://github.com/sam-w-yellin/crunch

https://redd.it/1psa0pg
@r_cpp

[Project] Parallax - Universal GPU Acceleration for C++ Parallel Algorithms

Hey r/cpp!

I'm excited to share **Parallax**, an open-source project that brings automatic GPU acceleration to C++ standard parallel algorithms.

# The Idea

Use `std::execution::par` in your code, link with Parallax, and your parallel algorithms run on the GPU. No code changes, no vendor lock-in, works on any GPU with Vulkan support (AMD, NVIDIA, Intel, mobile).

# Example

std::vector<float> data(1'000'000);
std::for_each(std::execution::par, data.begin(), data.end(),
[](float& x) { x *= 2.0f; });

With Parallax, this runs on the GPU automatically. 30-40x speedup on typical workloads.

# Why Vulkan?

* **Universal**: Works on all major GPU vendors
* **Modern**: Actively developed, not deprecated like OpenCL
* **Fast**: Direct compute access, no translation overhead
* **Open**: No vendor lock-in like CUDA/HIP

# Current Status

This is an early MVP (v0.1.0-dev):

* ✅ Vulkan backend (all platforms)
* ✅ Unified memory management
* ✅ macOS (MoltenVK), Linux, Windows
* 🔨 Compiler integration (in progress)
* 🔨 Full algorithm coverage (coming soon)

# Architecture

Built on:

* Vulkan 1.2+ for compute
* C ABI for stability
* LLVM/Clang for future compiler integration
* Lessons learned from vkStdpar

# Looking for Contributors

We need help with:

* LLVM/Clang plugin development
* Algorithm implementations
* Testing on different GPUs
* Documentation

# Links

* GitHub: [https://github.com/parallax-compiler/parallax-runtime](https://github.com/parallax-compiler/parallax-runtime)
* Docs: [https://github.com/parallax-compiler/parallax-docs](https://github.com/parallax-compiler/parallax-docs)
* License: Apache 2.0

Would love to hear your thoughts and feedback!

https://redd.it/1psfb7p
@r_cpp

CRTP-based Singleton with private construction token — looking for feedback

I experimented with a CRTP-based Singleton that enforces construction via a private token. Curious to hear thoughts.

So, I wanted to implement a singleton in my ECS crtp engine for design and architectural reasons, and I sat down to think about an efficient and crtp-friendly way to do this kind of pattern without necessarily having to alter the original Singleton class contract. The solution is a crtp-based Singleton in which the Derived (the original singleton) inherits from the base Singleton, which exposes the methods required for instantiation and the single exposure of the object. Simply put, instead of boilerplating the class with the classic Singleton code (op = delete), we move this logic and transform it into a proxy that returns a static instance of the derivative without the derivative even being aware of it.

In this way, we manage private instantiation with a struct token which serves as a specific specialization for the constructor and which allows, among other things, making the construction exclusive to objects that have this token.

This keeps the singleton type-safe, zero-cost, CRTP-friendly, and easy to integrate with proxy-based or ECS-style architectures.

Link to the GitHub repo

https://redd.it/1psmcaf
@r_cpp

Any Libraries for Asynchronous requests with HTTP2

Ive recently picked up C++ and am looking to port a program that i had previously written in python using aiohttp, but im having trouble finding a library that makes it easy to handle asynchronous http requests. I initially tried using liburing in conjunction with nghttp2, but quickly found that that was way over my level of knowledge. does anyone have any possible suggestions on what i should do. I cant use any libraries like boost because i need HTTP2 for its multiplexing capabilities.

https://redd.it/1psmrx6
@r_cpp

how i can share my projects in reddit if they run in console?

Should i send all code in messeage? Or file of my code? And if file, how?

https://redd.it/1pt0fdx
@r_cpp

Maintaining the Legacy: Total-Random takes over pcg-cpp maintenance (Support for Win ARM64, MSVC fixes, and Modern C++)

Hi everyone,

Like many of you, we consider the PCG (Permuted Congruential Generator) family of PRNGs by Prof. Melissa O'Neill to be the gold standard for performance and statistical quality. However, the original pcg-cpp repository has been inactive for over 3 years, leaving many critical community-submitted patches unmerged.

To ensure this vital library remains usable in modern development environments, we have formed Total-Random, a community-led organization dedicated to maintaining and modernizing legacy RNG libraries.

We have just released our first stable version of the Total-Random/pcg-cpp fork, which includes:

Windows ARM64 Support: Integrated fixes for ARM64 architecture (thanks to Demonese/LuaSTG).

MSVC Compatibility: Resolved C2678 ambiguous operator errors and other MSVC-specific build failures.

Empty Base Class Optimization (EBCO): Enabled __declspec(empty_bases) for MSVC to ensure optimal memory layout, matching GCC/Clang behavior.

Robust 128-bit Fallback: Improved handling for platforms lacking native __uint128_t support.

Improved unxorshift: Replaced the recursive implementation with a more efficient iterative doubling loop to prevent stack issues and improve clarity.

Our goal is to keep the library header-only, bit-for-bit compatible with the original algorithm, and ready for C++11/17/20/23.

Community Recognition: We are honored to have received early attention and feedback from researchers in the field, including Ben Haller (@bhaller) from Cornell University. You can see the community discussion regarding our transition here:https://github.com/imneme/pcg-cpp/issues/106

Check us out on GitHub: Total-Random/pcg-cpp



We welcome PRs, issues, and feedback from the community. Let's keep the best PRNG alive and kicking!



Best regards, The Total-Random Team

https://redd.it/1pt25rg
@r_cpp

Is my project good enough for CV?

Well, I’m currently a Polish IT student, and I’m looking for a job. Since I don’t have any professional experience yet, I decided to create something meaningful to put on my CV.

Initially, the idea was to build a parser that uses RPN to evaluate expressions. However, over time I kept adding more features: user-defined functions and variables, recursion, short-circuiting, assignment operations, references, local variables, sequential execution, loops, and multi-line input. All of this eventually required building an AST and dealing with a lot of pointer-related complexity.

I’ve gone through several refactorings (I still consider myself a beginner at programming) and even one complete rewrite of the code. I also noticed that there isn’t much detailed information about some parsing topics—at least beyond Wikipedia.

At this point, the project feels more like a very weak version of Desmos (without graphs) than just a calculator. Now I’m wondering: should I continue developing this project further, should I move on to something more complex, or is this already enough for a CV pet project?

Here’s the GitHub link in case anyone is interested:
https://github.com/YaroslavPryatkin/CoolCalculator

https://redd.it/1pt9veo
@r_cpp

Microsoft (CoreAI) is targeting to eliminate all C/C++ code by 2030
https://www.linkedin.com/posts/galenh_principal-software-engineer-coreai-microsoft-activity-7407863239289729024-WTzf?utm_source=share&utm_medium=member_ios&rcm=ACoAADgSZWYBfz-mLxzSdYSPqeNrByfljD_nKg4

https://redd.it/1ptokql
@r_cpp

iceoryx2 v0.8 released

It’s Christmas, which means it’s time for the iceoryx2 "Christmas" release!

Check it out: https://github.com/eclipse-iceoryx/iceoryx2 Full release announcement: https://ekxide.io/blog/iceoryx2-0.8-release/

iceoryx2 is a true zero-copy communication middleware designed to build robust and efficient systems. It enables ultra-low-latency communication between processes - comparable to Unix domain sockets or message queues, but significantly faster and easier to use.

The library provides language bindings for C, C++, Python, Rust, and C#, and runs on Linux, macOS, Windows, FreeBSD, and QNX, with experimental support for Android and VxWorks.

With this release we added the memory‑layout compatible types StaticString and StaticVector, which have Rust counterparts that let you exchange complex data structures between C++ and Rust without serialization.

The blackboard messaging pattern – a key‑value repository in shared memory that can be accessed from multiple processes – is now fully integrated, and the C++ language bindings are complete.

I wish you a Merry Christmas and happy hacking if you’d like to experiment with the new features!

https://redd.it/1ptyu8a
@r_cpp

A little Introduction to Control Flow Integrity - James McNellis - Keynote Meeting C++ 2025
https://www.youtube.com/watch?v=_eX7AVB4qzM

https://redd.it/1pty5kj
@r_cpp

tieredsort - 3.8x faster than std::sort for integers, header-only

Made a sorting library that detects data patterns before sorting.

Results (n=100k):

Random: 3.8x faster than std::sort, 1.6x faster than ska_sort

Dense data (ages, sensors): 30x faster than std::sort, 9x faster than ska_sort

The idea: real data isn't random. Ages are 0-100. Sensors are 12-bit. When the range is small, counting sort beats everything.

Detection cost: 12 comparisons + 64 samples. Negligible.

C++17, header-only, no SIMD needed.

GitHub: https://github.com/Cranot/tieredsort

Looking for feedback on edge cases I might have missed.

https://redd.it/1pu554f
@r_cpp

Is this the end of C++ at Microsoft?

Given the goals and push for Rust https://www.linkedin.com/posts/galenh_principal-software-engineer-coreai-microsoft-activity-7407863239289729024-WTzf

https://redd.it/1pu6cf7
@r_cpp

New 0-copy deserialization protocol

Hello all! Seems like serialization is a popular topic these days for some reason...

I've posted before about the c++ library "zerialize" (https://github.com/colinator/zerialize), which offers serialization/deserialization and translation across multiple dynamic (self-describing) serialization formats, including json, flexbuffers, cbor, and message pack. The big benefit is that when the underlying protocol supports it, it supports 0-copy deserialization, including directly into xtensor/eigen matrices.

Well, I've added two things to it:

1) Run-time serialization. Before this, you would have to define your serialized objects at compile-time. Now you can do it at run-time too (although, of course, it's slower).

2) A new built-in protocol! I call it "ZERA" for ZERo-copy Arena". With all other protocols, I cannot guarantee that tensors will be properly aligned when 'coming off the wire', and so the tensor deserialization will perform a copy if the data isn't properly aligned. ZERA _does_ support this though - if the caller can guarantee that the underlying bytes are, say, 8-byte aligned, then everything inside the message will also be properly aligned. This results in the fastest 0-copy tensor deserialization, and works well for SIMD etc. And it's fast (but not compact)! Check out the benchmark_compare directory.

Definitely open to feedback or requests!

https://redd.it/1pu6zwe
@r_cpp

Wait-Free Chunked I/O Buffer

We’re building a database and recently implemented a custom `I/O buffer` to handle the Postgres wire protocol. We considered `folly::IOBuf` and `absl::Cord`, but decided to implement a specialized version to avoid mutexes and simplify "late" size-prefixing.

**Key Technical Features:**

* **Chunked Storage:** Prevents large reallocations and minimizes `memcpy` by using a chain of fixed-size buffers.
* **Wait-Free:** Designed for high-concurrency network I/O without mutex contention.
* **Uncommitted Writes:** Allows reserving space at the start of a message for a size prefix that is only known after the payload is serialized, avoiding data shifts.

**Why custom?** Most generic "Cord" implementations were either slow or not truly concurrent. Our buffer allows one writer and one reader to work at the same time without locks and it actually works quite well to the benchmarks.

**Code & Details:**

* [Benchmarks & Blog Post](https://www.serenedb.com/blog/io-buffer)
* [Source Code (GitHub)](https://github.com/serenedb/serenedb/blob/main/libs/basics/message_buffer.h)

I'd love to hear your thoughts on our approach and if anyone has seen similar wins by moving away from `std::mutex` in their transport layers.

https://redd.it/1pu8cfs
@r_cpp

C++ is actually a great language for LLMs

I remember hearing a few months ago that c++ isn't a great language for tools like copilot, cursor or IDE replacements. Personally, it's really integrated into my workflow and I want to say I'm having a lot of positive experiences. So I wanted to share that a bit to those still in the mindset that these tools are a negative.

For one, I keep my scope small. I try to provide just the context it needs. Sometimes I will checkout the code of a third party library just so it can pull in that context if it needs. I can't provide all the best advice on this, because some of it has nothing to do with the language, other people have written great articles, and this is a skill you develop over time.

But for small and large wins, c++ is a great language. Questions like "are there any unnecessary string copies?", "are there any objects that are accidentally being passed by value?", to more beefy stuff like improving the performance of individual functions, or removing unnecessary blocks in your threading lifecycle. It understands the cost of memory allocations if you tell it that is important, flatten data structures to keep it contiguous, and it will adhere to the design of your codebase.

Anyway, I'm having a lot of fun with cursor in a c++ codebase and just wanted to evangelize a little - if you haven't integrated this into your codebase then you really are missing a very fundamental shift in software engineering role.

I will also say that there is such a variance in AI tools. I like neovim, but having to provide the context of individual files was painful. Cursor is able to use external tools to perform its job and search. The use of one vs the use of the other feel like performing a completely different role (neovim + plugins might be better now I don't know).

And a caveat: these tools can be used negatively and carelessly. I'm not here to argue that some form of SWE hasn't degraded, especially when you're working with coworkers who aren't taking care in their use. The trick is to keep the scope small, tell it what is important to you in your codebase, and increase the scope as you get more comfortable with the tool.

https://redd.it/1pu78s9
@r_cpp

Why do I rarely come across 'using namespace std?'

For context, I'm pretty new to this language. I'm about halfway through 'C++ A Beginners Guide by Herbert Schildt,' but I have explored the language past this book (embedded things).

In the book, the standard namespace is used for every program.
In C++ programs that I typically see, std:: is used (e.g., std::cout).

Is there a disadvantage to using the namespace? Is it that it's outdated?
(The book im reading is from the early 2000's)

https://redd.it/1pubujb
@r_cpp

All the other cool languages have try...finally. C++ says "We have try...finally at home."
https://devblogs.microsoft.com/oldnewthing/20251222-00/?p=111890

https://redd.it/1pudexb
@r_cpp

Any addition to my Roadmap.

C++ PROGRAMMING
Topics

GENERAL

ALGORITHMS AND DATA STRUCTURES
Data structures
- Arrays and Vectors
- Linked Lists
- Stacks and Queues
- Trees (BST, AVL, Red-Black)
- Graphs
- Hash Tables
- Heaps
Algorithms
- Sorting
- Searching
- Graph Algorithms
- Dynamic Programming
- Greedy Algorithms

CODE QUALITY
Core principles
- SOLID Principles
- DRY, KISS, YAGNI
Design Patterns
- Creational
- Structural
- Behavioral
Clean Code
- Naming Conventions
- Code Organization
Tools
- Linters
- Static Analyzers
- Profilers

C++ CORE

BASIC SYNTAX
Variables and Constants
Data Types
Operators
Comments
Input/Output (cin, cout)
Namespaces

CONTROL FLOW
Conditional Statements
- if, else if, else
- switch-case
Loops
- for, while, do-while
- Range-based for loop
Jump Statements
- break, continue, return
- goto

FUNCTIONS
Function Declaration
Function Definition
Function Overloading
Default Arguments
Inline Functions
Recursion
Function Pointers
Lambda Expressions

OBJECT-ORIENTED PROGRAMMING
Classes and Objects
- Class Definition
- Access Specifiers (public, private, protected)
- Member Functions
- Member Variables
Constructors
- Default Constructor
- Parameterized Constructor
- Copy Constructor
- Move Constructor
Destructors
this Pointer
Static Members
Friend Functions and Classes
Const Member Functions

INHERITANCE
Single Inheritance
Multiple Inheritance
Multilevel Inheritance
Hierarchical Inheritance
Virtual Base Classes
Access Control in Inheritance
Constructor/Destructor Order

POLYMORPHISM
Compile-time Polymorphism
- Function Overloading
- Operator Overloading
Runtime Polymorphism
- Virtual Functions
- Pure Virtual Functions
- Abstract Classes
- Virtual Destructors
Virtual Function Table (vtable)

ENCAPSULATION AND ABSTRACTION
Data Hiding
Getter and Setter Methods
Abstract Classes
Interfaces

POINTERS AND REFERENCES
Pointers
- Pointer Basics
- Pointer Arithmetic
- Pointers to Objects
- this Pointer
- Function Pointers
References
- Lvalue References
- Rvalue References
- Reference vs Pointer
Dynamic Memory
- new and delete
- new and delete
- Memory Leaks

TEMPLATES
Function Templates
Class Templates
Template Specialization
Variadic Templates
Template Metaprogramming
SFINAE

STANDARD TEMPLATE LIBRARY (STL)

CONTAINERS
Sequence Containers
- vector
- deque
- list
- array
- forwardlist
Associative Containers
- set, multiset
- map, multimap
Unordered Containers
- unorderedset
- unorderedmap
Container Adaptors
- stack
- queue
- priorityqueue

ITERATORS
Iterator Types
Iterator Operations
Iterator Invalidation
Reverse Iterators

ALGORITHMS
Non-modifying
- find, count, search
Modifying
- copy, move, transform
Sorting
- sort, stablesort, partialsort
Binary Search
Set Operations
Heap Operations

FUNCTORS AND LAMBDA
Function Objects
Lambda Expressions
std::function
std::bind

MODERN C++ (C++11/14/17/20/23)

C++11 FEATURES
Auto keyword
Range-based for loops
nullptr
Move

Any addition to my Roadmap.

C++ PROGRAMMING
Topics

GENERAL

ALGORITHMS AND DATA STRUCTURES
Data structures
- Arrays and Vectors
- Linked Lists
- Stacks and Queues
- Trees (BST, AVL, Red-Black)
- Graphs
- Hash Tables
- Heaps
Algorithms
- Sorting
- Searching
- Graph Algorithms
- Dynamic Programming
- Greedy Algorithms

CODE QUALITY
Core principles
- SOLID Principles
- DRY, KISS, YAGNI
Design Patterns
- Creational
- Structural
- Behavioral
Clean Code
- Naming Conventions
- Code Organization
Tools
- Linters
- Static Analyzers
- Profilers

C++ CORE

BASIC SYNTAX
Variables and Constants
Data Types
Operators
Comments
Input/Output (cin, cout)
Namespaces

CONTROL FLOW
Conditional Statements
- if, else if, else
- switch-case
Loops
- for, while, do-while
- Range-based for loop
Jump Statements
- break, continue, return
- goto

FUNCTIONS
Function Declaration
Function Definition
Function Overloading
Default Arguments
Inline Functions
Recursion
Function Pointers
Lambda Expressions

OBJECT-ORIENTED PROGRAMMING
Classes and Objects
- Class Definition
- Access Specifiers (public, private, protected)
- Member Functions
- Member Variables
Constructors
- Default Constructor
- Parameterized Constructor
- Copy Constructor
- Move Constructor
Destructors
this Pointer
Static Members
Friend Functions and Classes
Const Member Functions

INHERITANCE
Single Inheritance
Multiple Inheritance
Multilevel Inheritance
Hierarchical Inheritance
Virtual Base Classes
Access Control in Inheritance
Constructor/Destructor Order

POLYMORPHISM
Compile-time Polymorphism
- Function Overloading
- Operator Overloading
Runtime Polymorphism
- Virtual Functions
- Pure Virtual Functions
- Abstract Classes
- Virtual Destructors
Virtual Function Table (vtable)

ENCAPSULATION AND ABSTRACTION
Data Hiding
Getter and Setter Methods
Abstract Classes
Interfaces

POINTERS AND REFERENCES
Pointers
- Pointer Basics
- Pointer Arithmetic
- Pointers to Objects
- this Pointer
- Function Pointers
References
- Lvalue References
- Rvalue References
- Reference vs Pointer
Dynamic Memory
- new and delete
- new[] and delete[]
- Memory Leaks

TEMPLATES
Function Templates
Class Templates
Template Specialization
Variadic Templates
Template Metaprogramming
SFINAE

STANDARD TEMPLATE LIBRARY (STL)

CONTAINERS
Sequence Containers
- vector
- deque
- list
- array
- forward_list
Associative Containers
- set, multiset
- map, multimap
Unordered Containers
- unordered_set
- unordered_map
Container Adaptors
- stack
- queue
- priority_queue

ITERATORS
Iterator Types
Iterator Operations
Iterator Invalidation
Reverse Iterators

ALGORITHMS
Non-modifying
- find, count, search
Modifying
- copy, move, transform
Sorting
- sort, stable_sort, partial_sort
Binary Search
Set Operations
Heap Operations

FUNCTORS AND LAMBDA
Function Objects
Lambda Expressions
std::function
std::bind

MODERN C++ (C++11/14/17/20/23)

C++11 FEATURES
Auto keyword
Range-based for loops
nullptr
Move

Semantics
Perfect Forwarding
Smart Pointers
constexpr
Initializer Lists
Delegating Constructors

C++14 FEATURES
Generic Lambdas
Return Type Deduction
Binary Literals
Variable Templates

C++17 FEATURES
Structured Bindings
if/switch with initializers
std::optional
std::variant
std::any
Fold Expressions
Inline Variables

C++20 FEATURES
Concepts
Ranges
Coroutines
Modules
Three-way Comparison (<=>)
std::span

MEMORY MANAGEMENT
Stack vs Heap
RAII (Resource Acquisition Is Initialization)
Smart Pointers
- unique_ptr
- shared_ptr
- weak_ptr
Custom Allocators
Memory Pools

EXCEPTION HANDLING
try-catch blocks
throw keyword
Exception Classes
Standard Exceptions
noexcept specifier
Exception Safety Guarantees

FILE I/O
Stream Classes
- ifstream, ofstream, fstream
File Operations
Binary File I/O
String Streams
Formatting

MULTITHREADING
std::thread
Mutexes and Locks
Condition Variables
Atomic Operations
Thread-local Storage
Futures and Promises
async

PREPROCESSOR
Macros
#include
Header Guards
#pragma once
Conditional Compilation

ADVANCED TOPICS
Type Casting
- static_cast
- dynamic_cast
- const_cast
- reinterpret_cast
RTTI (Runtime Type Information)
Operator Overloading
Copy Elision and RVO
Perfect Forwarding
Name Mangling
Linkage

COMPILATION AND BUILD
Compilation Process
Header Files
Source Files
Linking
Build Systems
- Make
- CMake
Compiler Options

Requested a AI to provide a CPP roadmap to know CPP very thoroughly, and it has provided me this roadmap. Do you have additions? Or is this good for modern CPP?

https://redd.it/1pug6hs
@r_cpp