Message Handling with Boolean Algebra Ben Deane / CppCon / 2024-09-16 1Alternative Title "The Unreasonable Effectiveness of Boolean Algebra in Software Design, Showing the Particular Application of of a Message Handling Library, with an Excursion into the Roots of Programming" 2Frontmatter No AI/LLM was used in the creation of this talk. Code is simplified for slides; may have some errors in this talk is about The workings of a message-handling library. How messages and the fields in them are specified. Efficiently identifying (with matchers) a message coming off the wire. The role of Boolean

We need a system Orchestrator to implement the robot behaviorRobot Behaviors This Coordinator or Task Planner is also the highest level of abstraction of our system, where we focus on WHAT the robot (*value) * 2; return NodeStatus::SUCCESS; } else { std::cout << "missing [message]: ", value.error() << "\n"; return NodeStatus::FAILURE; } } }; ● Ports are an message="{A}"/> // prints "42" message="{B}"/> // prints "45.14" message="{msg}"/> // prints "hello world"

used when we created them.” - Albert EinsteinSo what is there to Rethink?Rethinking: Task Queues Problem #1 - Task Queues Do Not Scale Well: ● Contention: ○ Even the most meticulously designed lock-free problems: ○ Task starvation ○ Load balancing ○ Forfeits strict FIFO behaviour ○ Increases memory footprint (or requires allocations) ○ Terrible task selection “fairness” Task Thread Thread Thread Task Task Task Task Task Task Task Task Back Front Task Queue Execute Task() Thread Thread PoolRethinking: Task Queues Problem #2 - No Inherent Support For Prioritization: ● Priority queues address this but

in a top-down task graph What is Task Graph-based Programming System (TGPS) Code 4• TGPS encapsulates function calls and their dependencies in a top-down task graph What is Task Graph-based Programming top-down task graph What is Task Graph-based Programming System (TGPS) Code A B C D B A C D 6• TGPS encapsulates function calls and their dependencies in a top-down task graph What is Task Graph-based sched; 2 task_a = sched.emplace([](&){ 3 // Code block A; 4 }); 5 task_b = sched.emplace([](&){ 6 // Code block B; 7 }); 8 task_c = sched.emplace([](&){ 9 // Code block C; 10 }); 11 task_d = sched

ROS2 messages Simulator commands request for sensor data Sensor data simulator’s specific API/protocol Standard ROS2 messages© 2023 Apex.AI, Inc. | All rights reserved. Apex.AI, Apex.OS, Apex.Grace execution2 will always run computations in the same order. • Deterministic communication2 is when, for a message going from process A to process B, communication is guaranteed to be complete always before or an application in a completely event-based approach (SIL). Events can be: a. Sending/receiving a message b. A timer that expired 6. Test simulation scenarios in the CI© 2023 Apex.AI, Inc. | All rights

auto field for url and/or revision and you have uncommitted changes in your repository a warning message will be printed: 40 Chapter 5. Creating Packages Conan Documentation, Release 1.26.1 $ conan export upload' command will prevent uploading recipes with 'auto' values in these␣ ˓→fields. As the warning message explains, the auto fields won’t be replaced unless you specify --ignore-dirty, and by default, the libs = ["hello"] Typically, pre-compiled binaries come for different configurations, so the only task that the build() method has to implement is to map the settings to the different URLs. 42 Chapter

auto field for url and/or revision and you have uncommitted changes in your repository a warning message will be printed: 40 Chapter 5. Creating Packages Conan Documentation, Release 1.25.2 $ conan export upload' command will prevent uploading recipes with 'auto' values in these␣ ˓→fields. As the warning message explains, the auto fields won’t be replaced unless you specify --ignore-dirty, and by default, the libs = ["hello"] Typically, pre-compiled binaries come for different configurations, so the only task that the build() method has to implement is to map the settings to the different URLs. 42 Chapter

auto field for url and/or revision and you have uncommitted changes in your repository a warning message will be printed: 40 Chapter 5. Creating Packages Conan Documentation, Release 1.23.0 $ conan export upload' command will prevent uploading recipes with 'auto' values in these␣ ˓→fields. As the warning message explains, the auto fields won’t be replaced unless you specify --ignore-dirty, and by default, the libs = ["hello"] Typically, pre-compiled binaries come for different configurations, so the only task that the build() method has to implement is to map the settings to the different URLs. 42 Chapter

auto field for url and/or revision and you have uncommitted changes in your repository a warning message will be printed: 40 Chapter 5. Creating Packages Conan Documentation, Release 1.24.1 $ conan export upload' command will prevent uploading recipes with 'auto' values in these␣ ˓→fields. As the warning message explains, the auto fields won’t be replaced unless you specify --ignore-dirty, and by default, the libs = ["hello"] Typically, pre-compiled binaries come for different configurations, so the only task that the build() method has to implement is to map the settings to the different URLs. 42 Chapter

auto field for url and/or revision and you have uncommitted changes in your repository a warning message will be printed: 40 Chapter 5. Creating Packages Conan Documentation, Release 1.22.3 $ conan export upload' command will prevent uploading recipes with 'auto' values in these␣ ˓→fields. As the warning message explains, the auto fields won’t be replaced unless you specify --ignore-dirty, and by default, the libs = ["hello"] Typically, pre-compiled binaries come for different configurations, so the only task that the build() method has to implement is to map the settings to the different URLs. 42 Chapter