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Variant Visitation V2--Michael Park

By Adrien Hamelin | Jan 25, 2019 12:42 PM | Tags: performance advanced

Optimising accesses.

Variant Visitation V2

by Michael Park

From the article:

In 2015, I wrote an article titled Variant Visitation which described an implementation strategy for std::visit. The approach involved a matrix of function pointers, and many have raised concerns regarding poor code-gen caused by optimization limitations of function pointers on some compilers.

This post describes the switch-based approach implemented in mpark/variant, and its benchmark results...

The SoA Vector – Part 2: Implementation in C++--Sidney Congard

By Adrien Hamelin | Jan 3, 2019 01:10 PM | Tags: performance

The series continues and end.

The SoA Vector – Part 2: Implementation in C++

by Sidney Congard

From the article:

Like we saw in the first part of this series on SoA, the SoA is a way to organise the data of a collection of objects to optimise the performance of certain use cases: traversing the collection by accessing the same data member of all the objects:

struct person {
   std::string name;
   int age;
};

std::vector<person> persons = ...

for (auto& person : persons)
{
   ++person.age;
}
struct person {
   std::string name;
   int age;
};

std::vector<person> persons = ...

for (auto& person : persons)
{
   ++person.age;
}

The SoA in its barest expression is this:

struct persons {
    std::vector<std::string> names;
    std::vector<int> ages;
};
struct persons {
    std::vector<std::string> names;
    std::vector<int> ages;
};

By putting all the ages next to each other in memory, we optimise the performance of the traversal. But such a structure is not a container in itself, and is in particular not compatible with the STL.

Let’s design an SoA collection with an interface as close as possible to std::vector<persons>, but with the SoA structure of components stored in separate arrays...

CppCast Episode 180: Semantic Merge for C++ code, Plastic SCM and more on version control

By Jordi Mon Companys | Dec 21, 2018 07:18 AM | Tags: performance efficiency c++17 c++14

Episode 180 of CppCast the first podcast for C++ developers by C++ developers. In this episode Rob and Jason are joined by Pablo Santos from Códice Software the company that develops a merge tool that parses and merges even refactored C++ code:

CppCast Episode 180: Semantic Merge for C++ code, Plastic SCM and more on version control

About the interviewee:

Prior to entering start-up mode to launch Plastic SCM back in 2005, Pablo worked as R&D engineer in fleet control software development (GMV, Spain) and later digital television software stack (Sony, Belgium). Then he moved to a project management position (GCC, Spain) leading the evolution of an ERP software package for industrial companies. During these years he became an expert in version control and software configuration management working as a consultant and participating in several events as a speaker. Pablo founded Codice SoftwaLogo-semantic-vertical-negative.pngre in 2005 and since then is focused on his role as chief engineer designing and developing Plastic SCM and SemanticMerge among other SCM products.

The SoA Vector – Part 1: Optimizing the Traversal of a Collection--Sidney Congard

By Adrien Hamelin | Dec 20, 2018 02:08 PM | Tags: performance

It's all for speed.

The SoA Vector – Part 1: Optimizing the Traversal of a Collection

by Sidney Congard

From the article:

I like C++ because it offers a good compromise between writing expressive and fast code. But, I discovered a problem where I didn’t know any way to hide the implementation detail away from its use: The “Structure of Arrays” (SoA) versus the “Array of Structures” (AoS) problem.

This is the first part of a series of two articles:

  • what ‘SoA’ is about and what benefits it brings (part 1)
  • how to implement an SoA vector in C++ (part 2)

So let’s see what those SoA and AoS are all about...