today • Very quick review of concurrency and lock-free programming • Review the “bread and butter” of lock-free design patterns • Define wait-free algorithms, understand the definition and practical an elegant wait-free algorithm and wait-free design • Some simple benchmarks Some assumed knowledge • You know what std::atomic does and what it is used for • You’ve heard of lock-free programming and Obstruction free (progress in isolation): A single thread executed in isolation will complete the operation in a bounded number of steps. • Obstruction-free algorithms are immune to deadlock • Lock free (at

CPPCON 2020 / CPPCON 2020 / MACRO-FREE TESTING MACRO-FREE TESTING WITH C++20 WITH C++20 | | | | HTTPS://BOOST-EXT.GITHUB.IO/UT/CPPCON-2020 HTTPS://BOOST-EXT.GITHUB.IO/UT/CPPCON-2020 KRIS@JUSIAK SINGLE (2K LOC) WITH NO EXTERNAL DEPENDENCIES (2K LOC) WITH NO EXTERNAL DEPENDENCIES MACRO-FREE (✔ ) MACRO-FREE (✔ ) (*) LIMITATIONS MAY APPLY (*) LIMITATIONS MAY APPLY HTTPS://GITHUB.COM/BOOST-EXT/UT SINGLE (2K LOC) WITH NO EXTERNAL DEPENDENCIES (2K LOC) WITH NO EXTERNAL DEPENDENCIES MACRO-FREE (✔ ) MACRO-FREE (✔ ) FEATURES ( FEATURES ( , , , , , , , , , , , , , , ) (*) LIMITATIONS MAY APPLY

head) ● Busy polling on full / empty vs. sync using system calls ● Blocking / non blocking / wait-free ● Data ownership or just value propagation 13 CppCon 2024 | Erez Strauss | Lockfree, MPMC Queue instructions ● std::atomic - provides load / store / compare_exchange ● std::atomic::is_always_lock_free ● Load and Store of aligned 8 bytes ● CAS ( old-expected, new-value ) - atomic Compare And Swap

reliable sources such as Boost.Lockfree? ● Writing such a fifo is a fairly gentle introduction to lock free programming. ● There are some interesting performance optimizations that can be made. ● You may net/home/lock-free-algorithms/queues/unbounded-spsc-queue https://www.dpdk.org/ 3● Single producer: one producer (aka writer) thread ● Single consumer: one consumer (aka reader) thread ● Lock-free: it doesn’t doesn’t use mutex locks. At any point of time, some thread will make progress. ● Wait-free: each thread moves forward regardless of other threads. ● [Circular] Fifo [or Queue]: a single, fixed-size buffer

Deferred reclamation, i.e., garbage collection in C++ Some assumed knowledge • You’ve heard of lock-free programming and know what a compare_exchange is • You know roughly what atomic does and what it is Deferred reclamation, i.e., garbage collection in C++ Some assumed knowledge • You’ve heard of lock-free programming and know what a compare_exchange is • You know roughly what atomic does and what it is danielanderson.net std::atomic How many lines does it take to implement a lock-free & memory-safe stack? template struct Stack { struct Node { T t; shared_ptr

more than an order of magnitude greater than that to be found within Pascal enterprises.” Alan J. Perlis Forward, SICP“Pascal is for building pyramids – imposing, breathtaking, static structures but it is incredibly rewarding and fun to solve them (in whichever language you choose) • IT IS FREE! (as well as the MIT & Berkeley Lectures)To all the passionate teachers that inspire • Gerald Sussman

traditional tech companies (often with founder involvement) have increasingly directed more of their hefty free cash flows toward AI in efforts to drive growth and fend off attackers. And global competition – annualized using Q1:25 results. Source: Spotify, ‘The New York Post,’ ‘Inside Spotify: CEO Daniel Ek on AI, Free Speech & the Future of Music’ (5/2/25); Spotify earnings releases; eMarketer, ‘Spotify dominates intelligence, the [ceiling of our] ambitions is raised substantially. The potential for AI and robotics to free humanity from menial repetitive work and to dramatically increase the production of goods and services

banks, personal data, secrets, … Software safety (or “life safety” or similar) making software free from unacceptable risk of causing unintended harm to humans, property, or the environment examples: the available tools it presents to avoid undefined behavior in the C programs you write.” — Pascal Cuoq, Chief Scientist, Trustinsoft “An excellent introduction to modern C.” — Francis Glassborow the programmer can write it by hand, they’ll want to write it by generated code Examples: Types, free functions, specializations of std:: templates class(class) Foo { int func1(); public: void

kilogram * metre / square(second)> {} newton; inline constexpr struct pascal final : named_unit<"Pa", newton / square(metre)> {} pascal; inline constexpr struct joule final : named_unit<"J", newton * metre> kilogram * metre / square(second)> {} newton; inline constexpr struct pascal final : named_unit<"Pa", newton / square(metre)> {} pascal; inline constexpr struct joule final : named_unit<"J", newton * metre>

поділяються на дві великі категорії: • Повний контроль через ручне управління пам'яттю: C, C++, Pascal, ... – Програміст вирішує, коли виділяти або звільняти пам'ять купи. – Програміст повинен визначити Rust у контекст. • C має керувати купою вручну за допомогою malloc та free. Типові помилки включають забування виклику free, виклик free декілька разів для одного і того ж вказівника або розіменування вказівника та запозичення Rust у багатьох випадках дозволяє отримати продуктивність C, з операціями alloc та free саме там, де вони потрібні - з нульовими витратами. Він також надає інструменти, подібні до розумних