Relaxed Guide to memory_order_relaxed Hans Boehm Paul E. McKenney Google Facebook CPPCON 2020std::atomic/std::atomic_ref and memory_order_relaxed ● C++ atomic operations simple threads-as-interleaving semantics ● by passing memory_order enum values to explicit atomic operations. ● In particular, memory_order_relaxed allows arbitrary visibility reordering with respect memory_order_relaxed? ● Just a load, just a store: Full control, excellent efficiency and scalability! ○ Assuming aligned machine-sized atomic objects, that is…What is Not to Like About memory_order_relaxed

seemingly simple algorithms such as max and min. • We will also discuss the use of operator < in other order-related algorithms, showing how easy it is to make mistakes when using the operator < primitive All rights reserved. 20 An important insight • Given two values a and b, in that order: � Unless we find a reason to the contrary, … � min should prefer to return a, and … � max should min return the same item: � When values a and b are in order, min should return a / max should return b; … � When values a and b are out of order, min should return b / max should return a. 21 Copyright

execution (< 1μs) Low-latency strategy layer (1-10 μs)Order book deep dive “The order book is the heart of any trading system.” Larry Harris 12Order Book In a Nutshell 14 $92 $92 $95 50 $90 100 $85 price” at which you can sell is $92Order Book – Challenges 15 • Latency constraint for algorithmic trading ◦ Remember – it’s not just about being fast to send an order, but being fast to be accurate lowest price - Asks: from lowest to highest price $92 $92 $95 50 $90 100 $85 250 $95 50 $100 75Order Book – Properties 17 • Two ordered sequences - Bids: from highest to lowest price - Asks: from

achieving data determinism via: • Deterministic execution2 will always run computations in the same order. • Deterministic communication2 is when, for a message going from process A to process B, communication deterministic, the ROS application will be in free running mode and could have the impact that the order of messages coming from simulator bridge will not be the same sequence which triggers the running based Apex.Grace constructs related to determinism: 1. Executor management framework 2. Fixed-order execution coordinator based on executor Our proposal© 2023 Apex.AI, Inc. | All rights reserved.

functions and the avoidance of side effects ● Functional programming is identified by the use of higher order functions, pure functions, monads, declarative syntax What is Functional Programming?● A programming functions and the avoidance of side effects ● Functional programming is identified by the use of higher order functions, pure functions, monads, declarative syntax ○ C++ has all the tools to implement functional functions and the avoidance of side effects ● Functional programming is identified by the use of higher order functions, pure functions, monads, declarative syntax ○ C++ has all the tools to implement functional

template struct atomic_ref { T load(memory_order = memory_order::seq_cst) const noexcept; //... };} namespace sycl { template order DefaultOrder, memory_scope DefaultScope, access Space = access::address_space::generic_space> struct atomic_ref { T load(memory_order order = default_read_order, memory_scope scope = DefaultScope) const noexcept; //... };} ● std::atomic_ref template struct atomic_ref { T load(memory_order = memory_order::seq_cst) const noexcept; //... };} namespace sycl { template order DefaultOrder, memory_scope DefaultScope, access

Sorting Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1266 56.2 Order-Related Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1276 56.3 Sorting twice as it would be if the expression were written as v(1) < v(2) && v(2) <= v(3). However, the order of evaluations in a chained comparison is undefined. It is strongly recommended not to use expressions each element of an array A. 6.8 Operator Precedence and Associativity Julia applies the following order and associativity of operations, from highest precedence to lowest: For a complete list of every

Sorting Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1264 56.2 Order-Related Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1274 56.3 Sorting twice as it would be if the expression were written as v(1) < v(2) && v(2) <= v(3). However, the order of evaluations in a chained comparison is undefined. It is strongly recommended not to use expressions each element of an array A. 6.7 Operator Precedence and Associativity Julia applies the following order and associativity of operations, from highest precedence to lowest: Category Operators Associativity

Sorting Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263 56.2 Order-Related Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1273 56.3 Sorting twice as it would be if the expression were written as v(1) < v(2) && v(2) <= v(3). However, the order of evaluations in a chained comparison is undefined. It is strongly recommended not to use expressions each element of an array A. 6.7 Operator Precedence and Associativity Julia applies the following order and associativity of operations, from highest precedence to lowest: Category Operators Associativity

Sorting Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263 56.2 Order-Related Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1273 56.3 Sorting twice as it would be if the expression were written as v(1) < v(2) && v(2) <= v(3). However, the order of evaluations in a chained comparison is undefined. It is strongly recommended not to use expressions each element of an array A. 6.7 Operator Precedence and Associativity Julia applies the following order and associativity of operations, from highest precedence to lowest: Category Operators Associativity