Online Concurrency Workshop at C++ on Sea 2021

The restrictions brought upon us by COVID-19 are not over yet, and C++ on Sea is the latest conference that will be running as an online-only conference.

I will be running my More Concurrent Thinking class as an online workshop for C++ on Sea on 30th June and 1st July 2021.

The workshop will run from 09:30 UTC to 18:15 UTC each day. For attendees from North and South America, this is likely quite an early morning, and may be a late night for attendees from the far East, so please check the times in your local timezone.

Tickets include the full day of "normal" conference presentations on 2nd July 2021. Get yours from the C++ On Sea tickets page.

I hope to see you there!

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Online Concurrency Classes

With all the restrictions brought upon us by COVID-19, many C++ conferences are moving online.

This includes Cppcon and NDC Tech Town, both of which are being run as 100% virtual conferences this year.

I will be running my More Concurrent Thinking class as an online class for both conferences.

The class at NDC Tech Town will be a 2-day class running on 31st August 2020 and 1st September 2020, 9am - 5pm CEST, which is 0700 - 1500 UTC.

The class at Cppcon will be a 3-day class running on 9th September 2020 to 11th September 2020, 11am - 5pm EDT, which is 1500 - 2100 UTC.

The content is the same in both cases, though the timings are clearly different. Hopefully one or other fits in with your local timezone.

I hope to see you there!

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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.

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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!

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ACCU 2019 Slides and Trip Report

I attended ACCU 2019 a couple of weeks ago, where I was presenting my session Here's my number; call me, maybe. Callbacks in a multithreaded world.

The conference proper started on Wednesday, after a day of pre-conference workshops on the Tuesday, and continued until Saturday. I was only there Wednesday to Friday.

Wednesday

I didn't arrive until Wednesday lunchtime, so I missed the first keynote and morning sessions. I did, however get to see Ivan Čukić presenting his session on Ranges for distributed and asynchronous systems. This was an interesting talk that covered similar ground to things I've thought about before. It was good to see Ivan's take, and think about how it differed to mine. It was was also good to see how modern C++ techniques can produce simpler code than I had when I thought about this a few years ago. Ivan's approach is a clean design for pipelined tasks that allows implicit parallelism.

After the break I then went to Gail Ollis's presentation and workshop on Helping Developers to Help Each Other . Gail shared some of her research into how developers feel about various aspects of software development, from the behaviour of others to the code that they write. She then got us to try one of the exercises she talked about in small groups. By picking developer behaviours from the cards she provided to each group, and telling stories about how that behaviour has affected us, either positively or negatively, we can share our experiences, and learn from each other.

Thursday

First up on Thursday was Herb Sutter's keynote: De-fragmenting C++: Making exceptions more affordable and usable . Herb was eloquent as always, talking about his idea for making exceptions in C++ lower cost, so that they can be used in all projects: a significant number of projects currently ban exceptions from at least some of their code. I think this is a worthwhile aim, and hope to see something like Herb's ideas get accepted for C++ in a future standard.

Next up was my session, Here's my number; call me, maybe. Callbacks in a multithreaded world. It was well attended, with interesting questions from the audience. My slides are available here, and the video is available on youtube. Several people came up to me later in the conference to say that they had enjoyed my talk, and that they thought it would be useful for them in their work, which pleased me no end: this is what I always hope to achieve from my presentations.

Thursday lunchtime was taken up with book signings. I was one of four authors of recently-published programming books set up in the conservatory area of the hotel to sell copies of our books, and sign books for people. I sold plenty, and signed more, which was great.

Kate Gregory's talk on What Do We Mean When We Say Nothing At All? was after lunch. She discussed the various places in C++ where we can choose to specify something (such as const, virtual, or explicit), but we don't have to. Can we interpret meaning from the lack of an annotation? If your codebase uses override everywhere, except in one place, is that an accidental omission, or is it a flag to say "this isn't actually an override of the base class function"? Is it a good or bad idea to omit the names of unused parameters? There was a lot to think about with this talk, but the key takeaway for me is Consistency is Key: if you are consistent in your use of optional annotations, then deviation from your usual pattern can convey meaning to the reader, whereas if you are inconsistent then the reader cannot infer anything.

The final session I attended on Thursday was the C++ Pub Quiz, which was hosted by Felix Petriconi. The presented code was intended to confuse, and elicit exclamations of "WTF!", and succeeded on both counts. However, it was fun as ever, helped by the free drinks, and the fact that my team "Ungarian Notation" were the eventual winners.

Friday

Friday was the last day of the conference for me (though there the conference had another full day on Saturday). It started with Paul Grenyer's keynote on the trials and tribulations of trying to form a "community" for developers in Norwich, with meet-ups and conferences. Paul managed to be entertaining, but having followed Paul's blog for a few years, there wasn't anything that was new to me.

Interactive C++ : Meet Jupyter / Cling - The data scientist's geeky younger sibling was the next session I attended, presented by Neil Horlock. This was an interesting session about cling, a C++ interpreter, complete with a REPL, and how this can be combined with Jupyter notebooks to create a wiki with embedded code that you can edit and run. Support for various libraries allows to write code to plot graphs and maps and things, and have the graphs appear right there in the web page immediately. This is an incredibly powerful tool, and I had discussions with people afterwards about how this could be used both as an educational tool, and for "live" documentation and customer-facing tests: "here is sample code, try it out right now" is an incredibly powerful thing to be able to say.

After lunch I went to see Andreas Weis talk about Taming Dynamic Memory - An Introduction to Custom Allocators. This was a good introduction to various simple allocators, along with how and why you might use them in your C++ code. With John Lakos in the front row, Andreas had to field many questions. I had hoped for more depth, but I thought the material was well-paced, and so there wouldn't have been time; that would have been quite a different presentation, and less of an "introduction".

The final session I attended was Elsewhere Memory by Niall Douglas. Niall talked about the C++ object model, and how that can cause difficulties for code that wants to serialize the binary representation of objects to disk, or over the network, or wants to directly share memory with another process. Niall is working on a standardization proposal which would allow creating objects "fully formed" from a binary representation, without running a constructor, and would allow terminating the lifetime of an object without running its destructor. This is a difficult area as it interacts with compilers' alias analysis and the normal deterministic lifetime rules. However, this is an area where people currently do have "working" code that violates the strict lifetime rules of the standard, so it would be good to have a way of making such code standards-conforming.

Between the Sessions

The sessions at a conference at ACCU are great, and I always enjoy attending them, and often learn things. However, you can often watch these on Youtube later. One of the best parts of physically attending a conference is the discussions had in person before and after the sessions. It is always great to chat to people in person who you primarily converse with via email, and it is exciting to meet new people.

The conference tries to encourage attendees to be open to new people joining discussions with the "Pacman rule" — don't form a closed circle when having a discussion, but leave a space for someone to join. This seemed to work well in practice.

I always have a great time at ACCU conferences, and this one was no different.

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“The Developers” 2019 presentation and book signing

I will be presenting "Concurrency in C++20 and beyond" at The Developers 2019 in Romania on 23rd May 2019. Here is the abstract of my talk:

C++20 is set to add new facilities to make writing concurrent code easier. Some of them come from the previously published Concurrency TS, and others are new, but they all make our lives as developers easier. This talk will introduce the new features, and explain how and why we should use them.

The evolution of the C++ Concurrency support doesn't stop there though: the committee has a continuous stream of new proposals. This talk will also introduce some of the most important of these, including the new Executor model.

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

I look forward to seeing you there!

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ACCU 2019 presentation and book signing

The ACCU 2019 conference is running from 9th-13 April 2019, in Bristol, UK.

This year I will be presenting "Here's my number; call me, maybe. Callbacks in a multithreaded world" on 11th April. The abstract is:

A common pattern in multithreaded applications is the use of callbacks, continuations and task pipelines to divide the processing of data across threads. This has the benefit of ensuring that threads can quickly move on to further processing, and can minimize blocking waits, since tasks are only scheduled when there is work to be done.

The downside is that they can weave a tangled web of connections, and managing object lifetimes can now become complicated.

This presentation will look at ways of managing this complexity and ensuring that your code is as clear as possible, and there is no possibility of dangling references or leaked objects.

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

I look forward to seeing you there!

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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!

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Slides for my ACCU 2017 presentation

A couple of weeks ago I presented at the ACCU conference in Bristol (ACCU 2017). The title of my presentation was "Concurrency, Parallelism and Coroutines", and I was talking about the relationship between the Concurrency TS, the Coroutines TS and the Parallel algorithms from C++17:

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.

It was well attended, with a lot of interesting questions.

The slides are available here.

This year, my presentation was recorded. The video is available on youtube.

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C++ Concurrency in Action 2nd edition Early Access

I am happy to announce that the second edition of my book, C++ Concurrency in Action, is now available under the Manning Early Access Program.

The second edition is being updated to cover C++14, C++17 and the Concurrency TS, along with general improvements throughout the book.

This includes full coverage of the library changes from C++14 and C++17:

  • std::shared_mutex and std::shared_timed_mutex. These provide for multiple-reader/single-writer mutex locks.
  • std::scoped_lock from C++17 for locking multiple mutexes together.
  • Parallel overloads of many standard library algorithms include std::sort, std::for_each and std::transform_reduce.

Plus, full coverage of the library extensions from the concurrency TS:

  • std::experimental::latch to allow waiting for a set number of events to occur
  • std::experimental::barrier and std::experimental::flex_barrier to synchronize groups of threads
  • std::experimental::atomic_shared_ptr to allow atomic accesses to a single shared_ptr instance from multiple threads, as a better alternative that the std::atomic_load and std::atomic_store free functions.
  • Extended futures that allow continuations, so additional functions can be scheduled for when a future is ready.
  • std::experimental::when_all and std::experimental::when_any to allow waiting for either all of a set of futures to be ready, or the first of a set of futures to be ready.

Only the first few chapters are available at the moment, but if you sign up now, then you will get those chapters in PDF form now, as well as updated PDFs including the later chapters as they become ready, along with updates for the earlier ones, and a final print copy of the book when it's done.

50% Discount

If you use the code mlwilliams4 at the checkout when you sign up for the MEAP before 27th March 2017 then you'll get a 50% discount.

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