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CppCon 2023 Back to Basics: Initialization -- Ben Saks

By Blog Staff | Sep 15, 2023 07:00 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 some upcoming talks that you will be able to attend this year. Here’s another CppCon future talk we hope you will enjoy – and register today for CppCon 2023!

Back to Basics: Initialization

Wednesday, October 4 • 09:00 - 10:00

by Ben Saks

Summary of the talk:

C++ has many ways to initialize objects, and even experienced C++ programmers often have difficulty remembering exactly what each one means. For example, which constructor of T does each of the following statements invoke?

T t1(1, 2, 3);
T t2{4, 5, 6};
T t3 = t2;

Moreover, the context of the initialization can affect how the compiler interprets certain constructs. As such, we often have difficulty deciding which form of initialization to use. Choosing a form of initialization is especially difficult when we don’t know the exact type of the object that we’re initializing (i.e., when the type of the object is a template type parameter).

In this session, we’ll explore the similarities and differences among each form of C++ initialization and how the initialization rules have changed over time. Focusing on the common elements, we’ll see how C++’s initialization rules are (while not simple) not quite as complex as they might first appear. We’ll see how the Standard Library chooses which form of initialization to use and how that affects similar code that you might write yourself. We’ll also discuss how you can design your classes to make them easy to use in light of the initialization rules.

You’ll leave this session with a clearer understanding of exactly what each form of initialization means. With this knowledge, you’ll be better able to decide when each form of initialization suits your needs, which will help you write code that’s more expressive, robust, and maintainable.

CppCon 2023 Getting Build Tools to Talk to Each Other: Lessons Learned -- Diego Rodriguez-Losada

By Blog Staff | Sep 15, 2023 02:56 PM | Tags: None

A Common Package Specification: Getting Build Tools to Talk to Each Other: Lessons Learned From Making Thousands of Binaries Consumable by Any Build System

Tuesday, October 3 • 16:45 - 17:45

by Diego Rodriguez-Losada

Summary of the talk:

There is a lot of previous work and proposals for a “Common Package Specification”, but there has been little implementation experience with real-world production usage at scale with feedback from diverse groups, something critical for such a specification to be technically viable. Some mechanisms like CMake exported targets/config files are becoming more popular with the continuous adoption of CMake, and pkg-config (.pc) files are also a popular mechanism in GNU systems, but those are still tool-specific and it is still not possible nowadays to consume pre-built binaries in a generic way by every build system.

Since the Conan C++ package manager was released 7 years ago, one of its main design goals was to be tool agnostic and let any package created with any build system to be usable by any other build system. This talk will describe the abstraction that has been and is widely used by +1500 open source Conan packages covering the vast majority of popular C and C++ open source libraries, and thousands of teams using it in production for their own private packages. Based on this experience and the lessons learned, the talk will describe how a “Common Package Specification” should look like:

- Representation of the different folders necessary to define a package: include directories, library directories, binary directories, build files directories, etc.
- How paths should be relative so binary redistribution and re-usage in other machines is possible.
- Representation of the different preprocessor definitions, compiler flags, sysroot.
- Representation of “components”, when a package contains more than one library that can be optionally created, optionally consumed, and includes relationships between components.
- Representation of custom build-system “properties”, that allows to customize some behaviors for specific build systems.
- Achieving scalability by decoupling the binary requirements from the consuming specification (this talk focus only on the second one)

While this basic “Common Package Specification” can be easily represented and serialized in a file, like json or yaml that travels together with the package, there are some implementations challenges that will be discussed:

- How such a generic package specification maps to the existing popular build systems, including CMake, MSBuild, Autotools, Meson, etc, and how this mapping can be leveraged for faster adoption.
- In some cases, the same binary can provide different information to consumers like different preprocessor directives, based on some user configuration. How could this problem be solved with the typical declarative syntax of formats like json or yaml?
- How the packages and the “Common Package Specification” files are found and used by the build system?
- Is it possible to “consume” a package while it is still under development, so it doesn’t have the artifacts to consume in typical “include”, “lib” folders, but in a developer “source” layout?
- What happens at runtime? Beyond the common PATH, LD_LIBRARY_PATH, etc, some packages need to have defined some environment variables to correctly work. Can this information be included in the “Common Package Specification” too?
- Common operations over specification files, like aggregation of components or merging (in the right order, following the topological order of the graph), necessary for build-systems like autotools or NMake.

This talk will summarize years of real world experience contributing towards the goal of having a “Common Package Specification” for C and C++, that will allow full interoperability between build systems and package managers, one of the most desired and demanded functionalities in the C++ tooling ecosystem.

CppCon 2023 Taro: Task-graph-based Asynchronous Programming Using C++ Coroutines -- Dian-Lun Lin

By Blog Staff | Sep 15, 2023 09:00 AM | Tags: None

Taro: Task-graph-based Asynchronous Programming Using C++ Coroutines

Tuesday, October 3 • 16:45 - 17:45

by Dian-Lun Lin

Summary of the talk:

Task graph computing system (TGCS) plays an essential role in high-performance computing. Unlike loop-based models, TGCSs encapsulate function calls and their dependencies in a top-down task graph to implement irregular parallel decomposition strategies that scale to large numbers of processors, including manycore central processing units (CPUs) and graphics processing units (GPUs). As a result, recent years have seen a great deal amount of TGCS research, just name a few: Taskflow, oneTBB, Kokkos-DAG, and HPX. However, one common challenge faced by TGCSs is the issue of synchronization within each task. For instance, in scenarios where a task involves executing GPU operations, a CPU thread typically needs to wait until the GPU completes the operations before proceeding further. This synchronization overhead can hinder performance and limit the overall scalability of TGCSs.

The introduction of C++ coroutines in C++20 has revolutionized asynchronous programming, offering improved concurrency and expressiveness. However, integrating TGCS with C++ coroutines presents several challenges. Firstly, existing TGCS solutions are not compatible with C++ coroutines, as the coroutine paradigm deviates from traditional C++ programming. This incompatibility makes it difficult to seamlessly incorporate coroutines into existing TGCS frameworks. Secondly, C++ coroutine programming is extremely difficult and requires a solid understanding of the underlying concepts and mechanisms. The introduction of a new paradigm adds complexity and a steep learning curve for developers. Lastly, while C++ coroutines offer a powerful mechanism for managing asynchronous operations, designing and implementing an efficient scheduler to leverage their capabilities remains challenging. To fully exploit the benefits of C++ coroutines, there is a need for a specialized scheduler that can handle large numbers of coroutines and make optimal use of hardware resources.

To address these challenges, we present Taro: Task-Graph-Based Asynchronous Programming using C++ Coroutine. Taro offers a task-graph-based programming model for C++ coroutines, simplifying the expression of complex control flows and reducing development complexity. Additionally, Taro incorporates an efficient work-stealing scheduling algorithm tailored for C++ coroutines, minimizing unnecessary context switches, CPU migrations, and cache misses.

In this session, I will introduce Taro's programming model and demonstrate how Taro can enable efficient multitasking between CPU and GPU tasks, avoiding blocking wait on CPU threads for GPU tasks to finish. I will show the example code for using Taro. Finally, I will demonstrate how our solution can improve the performance of a real-world RTL simulation workload and microbenchmarks. Taro will be open-source and available on GitHub.

CppCon 2023 BehaviorTree.CPP: Task Planning for Robots and Virtual Agents -- Davide Faconti

By Blog Staff | Sep 14, 2023 07:48 PM | Tags: None

BehaviorTree.CPP: Task Planning for Robots and Virtual Agents

Tuesday, October 3 • 16:45 - 17:45

by Davide Faconti

Summary of the talk:

In this presentation, we will introduce BehaviorTree.CPP, a library that is becoming increasingly popular in robotics and used to implement Task Planning.
Behavior Trees are an alternative to Hierarchical Finite State Machines; this approach was originally used in the game industry.

In the first part of this presentation, we will teach what a Behavior Tree are and their advantages, when compared with Finite State Machines; we will also focus on the exclusive features that this library has, when compared to other open source alternatives.

In the second part, we will dive into the technical details of the implementation, in particular how we use design patterns such as Factory, Observer, Safe Type Erasure, Concurrency and even a custom embedded scripting language.

Inside STL: The deque, design -- Raymond Chen

By Blog Staff | Sep 14, 2023 04:17 PM | Tags: None

The C++ standard library deque is a double-ended queue that supports adding and removing items efficiently at either the front or the back.

Inside STL: The deque, design

By Raymond Chen

From the article:

All three of the major implementations of the C++ standard library use the same basic structure for a deque, but they vary in both policy and implementation details.

First, let’s design a simple version of a deque that stores its elements in an array.
template<typename T>
struct simple_deque
{
    T* elements;
    T* first;
    T* last;
    size_t capacity;
};
For example, a deque of three integers might look like this:

capacity = 8

size = last − first = 3

The elements points to an array whose length is given by the capacity member’s value of 8. In that array, the first three elements are not in use, but which could be used in the future. We’ll call them spares. Next come three elements holding the values 1, 2, and 3, followed by two more spares. The first element in use (1) is pointed to by first, and one past the last element in use is pointed to by last.

CppCon 2023 More Ranges Please -- Roi Barkan

By Blog Staff | Sep 14, 2023 02:45 PM | Tags: None

More Ranges Please

Tuesday, October 3 • 16:45 - 17:45

by Roi Barkan

Summary of the talk:

Ranges are one of the major additions of C++20, in which our main abstraction for sequences shifted from iterator-pairs into full fledged concepts, allowing better composability, expressibility and safety when working with bounded and even unbounded one dimensional sequences of data. The fluent use of the pipe-operator gave us power to write complex functional-style algorithms which are both highly readable and perfomant. The ranges library, especially with some recent C++23 additions also better exposes us to the notion of 'range-of-ranges' and multi-dimentional spans, which weren't in focus of the STL in prior versions of the language.

One key feature of the STL since the last century was the large number of algorithms and building blocks which seemed woven together and gave us a vocabulary by which algorithms could be expressed with little need to work with raw loops.

Together with the introduction of ranges, the STL has also gained various range-based algorithms (as well as views and adapters), yet most of those algorithms were basic adaptations of the ones that are available in the iterator-pair model.

In a talk from 2002, the primary designer of STL described the process of gathering, currating and solidifying the algorithms in the STL circa 1998 (Stepanov: STL and its Design Principles). My talk aims to apply a similar process to the universe of C++20/C++23 ranges, and propose potential additions to our vocabulary when developing range-based algorithms.

In this talk, we will start with a relatively theoretical introduction of the values and merrits of writing software systems as libraries, and get an introduction to the ranges library as an example of a breakthrough library.
Then, we will go over a variety of algorithms which currently don't exist for ranges, describe their potential value, and discuss whether they can or should be added to the standard.

A few examples of algorithms which will be covered:

Algorithms for sorted ranges, such as take_between and histogram, ...
Algorithm for ranges-of-(sorted-)ranges, such as merge, set_union, set_intersection, ...
Algorithms which might require some helper data structures, such as histogram (for non sorted ranges)
Algorithms related to generation and processing of permutations, such as order.
As we go through the various examples, we'll discuss what might be good candidates for addition to the STL (and reference prior talks on the topic), the notion of sorted ranges, and hopefully leave the talk with a good desire to compose algorithms in the brave new world of ranges

CppCon 2023 Visual Studio: Make Debugger, Diagnostics Improvements, Video Games, & More -- Li/Girmay

By Blog Staff | Sep 14, 2023 11:40 AM | Tags: None

What's New in Visual Studio: CMake Debugger, Diagnostics Improvements, Video Games, and More

Tuesday, October 3 • 15:15 - 16:15

by David Li and Mryam Girmay

Summary of the talk:

Another year of CppCon, another year of work on making Visual Studio a better IDE for everyone, no matter what platform you're targeting.

In this talk, we'll demonstrate the last year's work across the IDE, toolchain, vcpkg, and GitHub: leak sanitizer and advanced address sanitizer support for finding security holes, a host of tools for Unreal Engine, the new CMake Debugger, step-by-step macro expansion, and more. Catch up on improvements for highlights from previous years, such as Build Insights integration in Visual Studio and new tools for understanding complex template compilation errors

Come along to learn all about the latest in our tooling, and to get a peek into our future plans.

Meeting C++ live with Kevlin Henney

By Meeting C++ | Sep 14, 2023 09:22 AM | Tags: meetingcpp kevlinhenney community

Meeting C++ hosted an AMA with Kevlin Henney:

Meeting C++ live with Kevlin Henney

by Jens Weller & Kevlin Henney

Watch now:

CppCon 2023 std::linalg: Linear Algebra Coming to Standard C++ -- Mark Hoemmen

By Blog Staff | Sep 14, 2023 08:37 AM | Tags: None

std::linalg: Linear Algebra Coming to Standard C++

Tuesday, October 3 • 15:15 - 16:15

by Mark Hoemmen

Summary of the talk:

Many fields depend on linear algebra computations, which include matrix-matrix and matrix-vector multiplies, triangular solves, dot products, and norms. It's hard to implement these fast and accurately for all kinds of number types and data layouts. Wouldn't it be nice if C++ had a built-in library for doing that? Wouldn't it be even nicer if this library used C++ idioms instead of what developers have to do now, which is write nonportable, unsafe, verbose code for calling into an optimized Fortran or C library?

The std::linalg library does just that. It uses the new C++23 feature mdspan to represent matrices and vectors. The library builds on the long history and solid theoretical foundation of the BLAS (Basic Linear Algebra Subroutines), a standard C and Fortran interface with many optimized implementations. The C++ Standard Committee is currently reviewing std::linalg for C++26. The library already has two implementations that work with C++17 or newer compilers, and can take advantage of vendor-specific optimizations. Developers will see how std::linalg can make their C++ safer and more concise without sacrificing performance for use cases that existing BLAS libraries already optimize, while opening up new use cases and potential optimizations.

Standard C++ Foundation Annual Report for Fiscal Year 2023

By Blog Staff | Sep 14, 2023 12:46 AM | Tags: None

FY2023 Annual Report – Standard C++ Foundation

(fiscal year ending 2023-06-30)

Highlights

This fiscal year FY2023 from 2022-07-01 to 2023-06-30 was our third full year since the start of the pandemic, and the first year really recovering from the pandemic's effects. Although most of the Foundation’s work is done virtually, the pandemic did affect some of our prominent operations, including that CppCon 2021 and 2022 were held, but were hybrid for the first time. Planning is now well underway for Cpp 2023 which will fall into the next fiscal year, and will be back to onsite-only again for the first time since before the pandemic.

As in every recent year, the majority of funds received and spent in FY2023 were from running CppCon, which still had large expenses even though it was hybrid with mostly-online attendees in FY2022 and FY2023.

ETA: As we came out of the pandemic, per our financial assistance policy the Foundation resumed spending on supporting in-person ISO C++ standardization. In FY2022, the ISO C++ committee (WG21) resumed holding in-person meetings, with online Zoom participation; the Standard C++ Foundation paid in whole or in part for hosting three of the first four post-pandemic WG21 meetings, two of which fell into FY2023 and one of which will fall into FY2024 but was paid for in part in FY2023. The Foundation also provided financial travel assistance to four expert participants whose ISO C++ proposals had been encouraged by WG21 but who would not otherwise have been able to attend to progress their proposals. — Thank you very much once again to the Foundation's members and all the CppCon attendees and sponsors! Your support directly enables the Foundation to be able to pay for these ISO meetings and support ISO participants from around the world.

CppCon

Every year, the Foundation runs the CppCon conference, which is currently the largest C++ conference in the world. Since its inception in 2014, a goal for CppCon has been to help raise the bar for all C++ sister conferences. In our inaugural conference in 2014, we were the first C++ conference we know of to professionally record all talks and panels using a paid film crew, and make the videos available for free to everyone in the world; since then, several other conferences have followed suit, including that some have used the same video production company CppCon uses (Bash Films, which we can highly recommend). In each year since, we have continued to strive to add features, most recently professional in-room live captioning in 2019.

CppCon 2022 was held in September 2022. As with CppCon 2021, it was again a hybrid conference. This was essential because, although international governmental travel bans were mostly lifted, many companies still had travel restrictions in place due to Covid and/or the economic slowdown, and many attendees still were unable or reluctant to travel for understandable health reasons. Even so, CppCon 2022 squeaked out a new record in total attendance, with a much larger percentage of attendees returning on-site… for the first time since 2019, the exhibitor hall often felt crowded and the on-site experience felt like a normal bustling conference again!

CppCon 2023 is being held later than usual this year, and planning is still underway. The talk submissions came in right at the end of FY2022, so we do know it has the second-highest number of talk submissions ever (second only to pre-pandemic 2019). So far, we know it will be even busier on-site than last year with more attendees, volunteers, and exhibitors than last year. We thank all our sponsors, exhibitors, volunteers, and attendees, and we look forward to seeing all of them in person at our first all-in-person event since 2019.

The professionally recorded C++ videos are made available worldwide at no charge on the CppCon YouTube channel. Here are some basic channel statistics:

combined viewership: 25.4 million views
total watch time: 4.9 million hours
channel subscribers: over 134,000

Next report

Our next annual report will cover the fiscal year from 2023-07-01 to 2024-06-30. Besides being published here, the annual report will also be given as usual as a live presentation at our annual Foundation members meeting which is held during the week of the autumn WG21 meeting.

About the Standard C++ Foundation

The Standard C++ Foundation (Standard CPP Foundation in some databases that don’t support + in names) is a Washington 501(c)(6) not-for-profit organization whose purpose is to support the C++ software developer community and promote the understanding and use of modern Standard C++ on all compilers and platforms. We do this by operating and funding isocpp.org, the github.com/isocpp and github.com/cplusplus repositories, the CppCon conference including CppCon.org and the CppCon YouTube channel, and providing financial assistance support for WG21 (ISO C++ committee) standards meetings for meeting hosting costs, travel assistance for attendees in financial need, and grants to progress WG21 proposals that have been encouraged but whose the authors cannot progress further without some financial assistance and that the WG21 major subgroup chairs have approved funding.

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The “Standard C++ Foundation” name and stylized “C++” logo are trademarks of the Standard C++ Foundation. See isocpp.org/home/terms-of-use.