Concurrency Patterns -- Rainer Grimm

By Blog Staff | May 30, 2023 11:28 AM | Tags: None

There are many well-established patterns used in the concurrency domain. They deal with synchronization challenges such as sharing and mutation but also with concurrent architectures. Today, I will introduce and dive deeper into them in additional posts.

Concurrency Patterns

by Rainer Grimm

From the article:

The main concern when you deal with concurrency is shared, mutable state or, as Tony Van Eerd put it in his CppCon 2014 talk “Lock-free by Example”: “Forget what you learned in Kindergarten (ie stop Sharing)”. A crucial term for concurrency is a data race. Let me first define this term.

• Data race: A data race is when at least two threads access a shared variable simultaneously. At least one thread tries to modify the variable. If your program has a data race, it has undefined behavior. This means all outcomes are possible, so reasoning about the program makes no sense anymore.

A necessary condition for a data race is a mutable, shared...

Mutating Through a Filter -- Barry Revzin

By Blog Staff | May 26, 2023 02:07 PM | Tags: None

Nico Josuttis gave a talk recently that included an example and I wanted to explain what’s going on in this example, what the issue is, and what (if anything) is broken.

Mutating Through a Filter

by Barry Revzin

From the article:

As with a lot of my explanations, we have to start from the beginning.

The C++ iterator model has a number of iterator categories: input, forward, bidirectional, random access, and (since C++20) contiguous. This post only needs to consider the first two.

An input range (a range whose iterator is an input iterator) is a single-pass range. You can only ever call begin() one time on it. You can’t have multiple different input iterators into the same range - incrementing one immediately invalidates any existing copies.

CppCon 2022 How Microsoft Uses C++ to Deliver Office - Huge Size, Small Components -- Zachary Henkel

By Blog Staff | May 26, 2023 02:06 PM | Tags: None

Registration is now open for CppCon 2023! The conference starts on October 1 and will be held in person in Aurora, CO. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from last year's conference. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2023!

How Microsoft Uses C++ to Deliver Office - Huge Size, Small Components

by Zachary Henkel

Summary of the talk:

Office is one of the largest and longest-lived C++ codebases in the world. Over 40 years Office has evolved from a single application written in C for DOS to a product containing over 100M lines of C++ code targeting more than a dozen platforms. What are the implications of growing to this size and what sort of engineering is required? In this talk I’ll give a glimpse behind the curtain on the C++ engineering and architecture in Office. In addition to sharing some details on the scale of Office, I’ll describe the design and coding standards used to create well-factored components that we have termed liblets.

CppCon 2022 Back to Basics: C++ API Design -- Jason Turner

By Blog Staff | May 25, 2023 01:42 PM | Tags: None

Registration is now open for CppCon 2023! The conference starts on October 1 and will be held in person in Aurora, CO. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from last year's conference. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2023!

Back to Basics: C++ API Design

by Jason Turner

Summary of the talk:

Let’s face it: writing a C++ API can be a daunting task. You recognize that APIs are a critical aspect of your code, and you’d like to provide your users with a great experience, but how?

This talk will focus on one key aspect: "Making APIs Hard to Use Wrong." How do we design APIs that help, instead of hurt, our users?

Modern C++ In-Depth — Is string_view Worth It?

By Jens Maurer | May 25, 2023 06:46 AM | Tags: c++17 basics

An introduction to std::string_view

Modern C++ In-Depth — Is string_view Worth It?

by Michael Kristofik

From the article:

std::string_view makes it easier to write generic code that can accept read-only references to character sequences, regardless of the underlying container that holds that data. ... However, like normal references, there is potential for misuse.

How To Check If A Pointer Is In A Range Of Memory -- Raymond Chen

By Blog Staff | May 24, 2023 08:09 AM | Tags: None

C language was defined to cover a large range of computer architectures, including many which would be considered museum relics today. It therefore takes a very conservative view of what is permitted, so that it remains possible to write C programs for those ancient systems. (Which weren’t quite so ancient at the time.)

How To Check If A Pointer Is In A Range Of Memory

by Raymond Chen

From the article:

Suppose you have a range of memory described by two variables, say,

byte* regionStart;
size_t regionSize;

And suppose you want to check whether a pointers lies within that region. You might be tempted to write

if (p >= regionStart && p < regionStart + regionSize)

but is this actually guaranteed according to the standard?

2023-05 Mailing Available

By Administrator | May 23, 2023 08:51 AM | Tags: None

The 2023-05 mailing of new standards papers is now available.

CppCon 2022 10 Tips for Cleaner C++ 20 Code -- David Sackstein

By Blog Staff | May 23, 2023 06:21 AM | Tags: None

Registration is now open for CppCon 2023! The conference starts on October 1 and will be held in person in Aurora, CO. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from last year's conference. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2023!

10 Tips for Cleaner C++ 20 Code

by David Sackstein

Summary of the talk:

The objective of this session is to provide guidelines and tips that will help the audience write readable, testable and extensible code with modern C++.

One of the greatest challenges we face, as programmers, is to make sure that our code can be understood and used by our colleagues - and not only by the compiler.

As the complexity of C++ increases, the compiler is able to deduce and optimize more of our code, but often at the cost of making it more obscure for our colleagues. Code that is difficult to read is difficult to test, to maintain and to extend.

In the session, I propose to help the audience understand the core problems that we introduce as our programming becomes more advanced, and how we can avoid them. The main part of the session will discuss some fairly complex and advanced C++ code which is difficult to understand. I will then demonstrate 10 easily applicable tips to make it easier to understand and to test. The benefits will be clearly evident.

There will also be a short discussion with the audience to increase the confidence that the guidelines and the tips are readily applicable in their own diverse projects.

More than a rehash – Joaquín M. López in Madrid at Using std::cpp

By Jordi Mon Companys | May 23, 2023 03:35 AM | Tags: community

In this talk, Joaquín will invite you to look under boost::unordered_flat_map's hood with him and learn about this container's data structure, its key design elements and how it compares with other top-performance C++ hashmaps both in theory and in practice.

More than a rehash – Joaquín M. López in Madrid at Using std::cpp
by Joaquín M. López

From the talk:

Boost 1.81 (Dec 2022) released boost::unordered_flat_map, a hashmap (unordered associative container in C++ parlance) that relies on open addressing and SIMD techniques to provide extremely high performance. In this talk, Joaquín will invite you to look under boost::unordered_flat_map's hood with him and learn about this container's data structure, its key design elements and how it compares with other top-performance C++ hashmaps both in theory and in practice. The talk finishes with a teaser on concurrent hashmaps arriving as part of your Boost update later this year. Deck and note can be found here. 

Why is std::hardware_destructive_interference_size a Compile-time Constant ... -- Raymond Chen

By Blog Staff | May 22, 2023 03:03 PM | Tags: None

C++17 added a new compile time constant std::hardware_destructive_interference_size which tells you (basically) the size of a cache line. The purpose of this is to allow you to lay out your structures in a way that avoids false sharing.

Why is std::hardware_destructive_interference_size a Compile-time Constant Instead of a Run-time Value?

by Raymond Chen

From the article:

C++17 added a new compile time constant std::hardware_destructive_interference_size which tells you (basically) the size of a cache line. The purpose of this is to allow you to lay out your structures in a way that avoids false sharing.¹

But how does the compiler know what the cache line size will be of the CPU the program will eventually be run on? Shouldn’t this be a run-time value instead of a compile-time value?

Well yes, the actual size of the cache line isn’t know until run-time, because it is only then that the program meets a CPU. But really, you want this to be a ...