Introduction to Wait-free Algorithms in C++ Programming - Daniel Anderson - CppCon 2024

Video Description

https://cppcon.org​ --- Introduction to Wait-free Algorithms in C++ Programming - Daniel Anderson - CppCon 2024 --- If you've attended any talks about concurrency, you've no doubt heard the term "lock-free programming" or "lock-free algorithms". Usually these talks will give you a slide that explains vaguely what this means, but you accept that is is approximately (but not quite exactly) equal to "just don't use locks". More formally, lock-freedom is about guaranteeing how much progress your algorithm will make in a given time. Specifically, a lock-free algorithm will always make some progress on at least one operation/thread. It does not guarantee however that all threads make progress. In a lock-free algorithm, a particular operation can still be blocked for an arbitrary long time because of the actions of other contending threads. What can we do in situations where this is unacceptable, such as when we want to guarantee low latency for every operation on our data structure rather than just low average latency? In these situations, there is a stronger progress guarantee that we can aim for called wait-freedom. An algorithm is wait free if *every* operation is guaranteed to make progress in a bounded amount of time, i.e., no thread can ever be blocked for an arbitrarily long time. This helps to guarantee low tail latency for all operations, rather than low average latency in which some operations are left behind. In this talk, we will give an introduction to designing and implementing wait-free algorithms. Without assuming too much background of the audience, we will review the core ideas of lock-free programming and understand the classic techniques for transforming a blocking algorithm into a lock-free one. The main bread-and-butter technique for lock-free algorithms is the compare-exchange loop or "CAS loop", in which an operation reads the current state of the data structure, creates some sort of updated version, and then attempts to install the update via a compare-exchange, looping until it succeeds. compare-exchange loops suffer under high contention since the success of one operation will often cause another to have to repeat work until they succeed. The bread-and-butter technique of wait-free programming that overcomes this issue is helping. When operations contend, instead of racing to see who wins, an operation that encounters another already-in-progress operation attempts to help it complete first, then proceeds with its own operation. This results in the initial operation succeeding instead of being clobbered and forced to try again. --- Slides: https://github.com/CppCon/CppCon2024/blob/main/Presentations/When_Lock-Free_Still_Isn't_Enough.pdf Sponsored by JetBrains: https://www.jetbrains.com/clion/ --- Daniel Anderson Daniel Anderson is an assistant teaching professor at Carnegie Mellon University, where he recently graduated with a PhD in computer science focusing on parallel computing and parallel algorithms. Daniel teaches algorithms classes to hundreds of undergraduate students and spends his remaining time writing C++ libraries that aim to make parallel computing easier and more accessible to non-experts. He is the recipient of a Best Paper Award from the ACM Symposium on Parallelism in Algorithms and Architecture (SPAA) conference. --- CppCon is the annual, week-long face-to-face gathering for the entire C++ community. The conference is organized by the C++ community for the community. You will enjoy inspirational talks and a friendly atmosphere designed to help attendees learn from each other, meet interesting people, and generally have a stimulating experience. Taking place this year in Aurora, Colorado, near the Denver airport, and including multiple diverse tracks, the conference will appeal to anyone from C++ novices to experts. Annual CppCon Conference - https://www.cppcon.org https://www.linkedin.com/company/cppcon https://x.com/cppcon https://www.facebook.com/CppConference https://www.reddit.com/r/cppcon/ https://mastodon.social/@CppCon --- Videos Filmed & Edited by Bash Films: http://www.BashFilms.com YouTube Channel Managed by Digital Medium Ltd: https://events.digital-medium.co.uk --- #concurrency #cpp #cplusplus #cppcon #cppprogramming #cplusplusprogramming #softwaredevelopment #softwareengineering #coding #code #technology #technews #programming #programmer