2-day More Concurrent Thinking class at CppCon 2022

I am excited to be going to CppCon again this year, where I will be running a 2-day class: More Concurrent Thinking in C++: Beyond the Basics.

The class is onsite at the conference venue in Aurora, Colorado, USA, on Saturday 10th September 2022 and Sunday 11th September 2022, immediately before the main conference.

I'll be teaching you to think about the synchronization properties of the constructs you use, and how to work with the low level facilities provided by the C++20 standard to build high level abstractions. We'll look at actors, thread pools and executors, and how to design code that works with those abstractions.

We'll look at how to use low-level atomic operations to build lock-free data structures, and the issues that can arise when doing so. We'll also look at how scalability concerns can impact your design choices.

Finally, we'll look at the important issue of testing multithreaded code, and the tools we can use to help us find the causes of problems.

If this sounds interesting, sign up for the class when you register for the main conference.

I'll also be doing a presentation on Tuesday: An Introduction to Multithreading in C++20. This is a whistle-stop tour of the multithreading features of C++20, briefly covering each feature and what it is used for, and which you should choose by default.

Whether you come to my class and presentation or not, I hope to see you there!

Posted by Anthony Williams
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CppCon 2019 Trip Report and Slides

Having been back from CppCon 2019 for over a week, I thought it was about time I wrote up my trip report.

The venue

This year, CppCon was at a new venue: the Gaylord Rockies Resort near Denver, Colorado, USA. This is a huge conference centre, currently surrounded by vast tracts of empty space, though people told me there were many plans for developing the surrounding area.

There were hosting multiple conferences and events alongside CppCon; it was quite amusing to emerge from the conference rooms and find oneself surrounded by people in ballgowns and fancy evening wear for an event in the nearby ballroom!

There were a choice of eating establishments, but they all had one thing in common: they were overpriced, taking advantage of the captured nature of the hotel clientelle. The food was reasonably nice though.

The size of the venue did make for a fair amount of walking around between sessions.

Overall the venue was nice, and the staff were friendly and helpful.

Pre-conference Workshop

I ran a 2-day pre-conference class, entitled More Concurrent Thinking in C++: Beyond the Basics, which was for those looking to move beyond the basics of threads and locks to the next level: high level library and application design, as well as lock-free programming with atomics. This was well attended, and I had interesting discussions with people over lunch and in the evening.

If you would like to book this course for your company, please see my training page.

The main conference

Bjarne Stroustrup kicked off the main conference with his presentation on "C++20: C++ at 40". Bjarne again reiterated his vision for C++, and outlined some of the many nice language and library features we have to make development easier, and code clearer and less error-prone.

Matt Godbolt's presentation on "Compiler Explorer: Behind the Scenes" was good and entertaining. Matt showed how he'd evolved Compiler Explorer from a simple script to the current website, and demonstrated some nifty things about it along the way, including features you might not have known about such as the LLVM instruction cost view, or the new "run your code" facility.

In "If You Can't Open It, You Don't Own It", Matt Butler talked about security and trust, and how bad things can happen if something you trust is compromised. Mostly this was obvious if you thought about it, but not something we necessarily do think about, so it was nice to be reminded, especially with the concrete examples. His advice on what we can do to build more secure systems, and existing and proposed C++ features that help was also good.

Barbara Geller and Ansel Sermersheim made an enthusiastic duo presenting "High performance graphics and text rendering on the GPU for any C++ application". I am excited about the potential for their Copperspice wrapper for the Vulkan rendering library: rendering 3D graphics portably is hard, and text more so.

Andrew Sutton's presentation on "Reflections: Compile-time Introspection of Source Code" was an interesting end to Monday. There is a lot of scope for eliminating boilerplate if we can use reflection, so it is good to see the progress being made on it.

Tuesday morning began with a scary question posed by Michael Wong, Paul McKenney and Maged Michael: "Will Your Code Survive the Attack of the Zombie Pointers?" Currently, if you delete an object or call free then all copies of those pointers immediately become invalid across all threads. Since invalid pointers can't even be compared, this can result in zombies eating your brains. Michael, Paul and Maged looked at what we can do in our code to avoid this, and what they are proposing for the C++ Standard to fix the problem.

Andrei Alexandrescu's presentation on "Speed is found in the minds of people" was an insightful look at optimizing sort. Andrei showed how compiler and processor features mean that performance can be counter-intuitive, and code with a higher algorithmic complexity can run faster in the right conditions. Always use infinite loops (except for most cases).

I love the interactive slides in Hana Dusikova's presentation "A State of Compile Time Regular Expressions". She is pushing the boundaries of compile-time coding to make our code perform better at runtime. std::regex can be slow compared to other regular expression libraries, but ctre can be much better. I am excited to see how this can be extended to compile-time parsing of other DSLs.

In "Applied WebAssembly: Compiling and Running C++ in Your Web Browser", Ben Smith showed the use of WebAssembly as a target to allow you to write high-performance C++ code that will run in a suitable web browser on any platform, much like the "Write once, run anywhere" promise of Java. I am interested to see where this can lead.

Samy Al Bahra and Paul Khuong presented the final session I attended: "Abusing Your Memory Model for Fun and Profit". They discussed how they have written code that relies on the stronger memory ordering requirements imposed by X86 CPUs over and above the standard C++ memory model in order to write high-performance concurrent data structures. I am intrigued to see if any of their techniques can be used in a portable fashion, or used to improve Just::Thread Pro.

Whiteboard code

This year there were a few whiteboards around the conference area for people to use for impromptu discussions. One of them had a challenge written on it:

"Can you write a requires expression that ensures a class has a member function with a specified signature?"

This led to a lot of discussion, which Arthur O'Dwyer wrote up as a blog post. Though the premise of the question is wrong (we shouldn't want to constrain on such specifics), it was fun, interesting and enlightening trying to think how one might do it — it allows you to explore the corner cases of the language in ways that might turn out to be useful later.

My presentation

As well as the workshop, I presented a talk on "Concurrency in C++20 and beyond", which was on Tuesday afternoon. It was in an intermediate-sized room, and I believe was well attended, though it was hard to see the audience with the bright stage lighting. There were a number of interesting questions from the audience addressing the issues raised in my presentation, which is always good, though the acoustics did make it hard to hear some of them.

Slides are available here.

~trip_report()

So that was an overview of another awesome CppCon. I love the in-person interactions with so many people involved in using C++ for such a wide variety of things. Everyone has their own perspective, and I always learn something.

The videos are being uploaded incrementally to the CppCon YouTube channel, so hopefully the video of my presentation and the ones above that aren't already available will be uploaded soon.

Posted by Anthony Williams
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CppCon 2019 Class, Presentation and Book Signing

It is now less than a month to this year's CppCon, which is going to be in Aurora, Colorado, USA for the first time this year, in a change from Bellevue where it has been for the last few years.

The main conference runs from 15th-20th September 2019, but there are also pre-conference classes on 13th and 14th September, and post-conference classes on 21st and 22nd September.

I will be running a 2-day pre-conference class, entitled More Concurrent Thinking in C++: Beyond the Basics, which is for those looking to move beyond the basics of threads and locks to the next level: high level library and application design, as well as lock-free programming with atomics. You can book your place as part of the normal CppCon registration.

I will also be presenting a session during the main conference on "Concurrency in C++20 and beyond".

Finally, I will also be signing copies of the second edition of my book C++ Concurrency In Action now that it is in print.

I look forward to seeing you there!

Posted by Anthony Williams
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CppCon 2017 class and presentation on concurrency

I am pleased to announce that I will be running my "Concurrent Thinking in C++" class at CppCon again this year. Here is the course description:

One of the most difficult issues around designing software with multiple threads of execution is synchronizing data.

Whether you use actors, active objects, futures and continuations or mutable shared state, every non-trivial system with multiple threads needs to transfer data between them. This means thinking about which data needs to be processed by which thread, and ensuring that the right data gets to the right threads in the right order. It also means thinking about API design to avoid race conditions.

In this workshop you will encounter a series of scenarios involving multithreaded code, and be guided through identifying the problem areas and the ways of handling them.

You will learn techniques for thinking about the scenarios to ease the analysis, as well as details of the tools we have available in C++ to mitigate the problems. You will also learn how to use the C++ standard library to help enforce the requirements of each scenario in code.

I will also be presenting on "Concurrency, Parallelism and Coroutines":

C++17 is adding parallel overloads of most of the Standard Library algorithms. There is a TS for Concurrency in C++ already published, and a TS for Coroutines in C++ and a second TS for Concurrency in C++ in the works.

What does all this mean for programmers? How are they all related? How do coroutines help with parallelism?

This session will attempt to answer these questions and more. We will look at the implementation of parallel algorithms, and how continuations, coroutines and work-stealing fit together. We will also look at how this meshes with the Grand Unified Executors Proposal, and how you will be able to take advantage of all this as an application developer.

My class is on 17th-18th September, and the main conference is running 19th-23rd, with my presentation on 20th September. If you haven't got your ticket already, head on over to CppCon Registration to get yours now.

Hope to see you there!

Posted by Anthony Williams
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