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

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

unifex::static_thread_pool pool; io_uring_context ctx; unifex::task task = async_main({argv + 1, argc - 1}, pool, ctx); unifex::sync_wait(std::move(task)); return 0; }int main(int argc, char** argv) { unifex::static_thread_pool pool; io_uring_context ctx; unifex::task task = async_main({argv + 1, argc - 1}, pool, ctx); unifex::sync_wait(std::move(task)); return 0; }int main(int argc, char** argv) { unifex::static_thread_pool pool; io_uring_context ctx; unifex::task task = async_main({argv + 1, argc - 1}, pool, ctx); unifex::sync_wait(std::move(task)); return 0; }int main(int argc, char** argv) {

careA typical async framework class Task { ... } represents a unit of background work Task::join() explicit call to suspend the current task until another task completes, and returns its result propagates uncaught exceptions Task::detach() allows the task to run alongside the rest of the programDetached tasks considered harmful // don’t do this void bad(tcp::socket& s) { std::array asio::use_awaitable); }, asio::detached); } No way to figure out task lifetime => no automatic object lifetime managementDetached tasks considered harmful // don’t do

understanding the general behavior only. template struct task; task sum(int a, int b) { int result = a + b; co_return result; } task sum4(int a, int b, int c, int d) { int ab = co_await initial_suspend_awaitable_t initial_suspend_awaitable; final_suspend_awaitable_t final_suspend_awaitable; }; }; task sum(int a, int b) { auto frame = make_unique<__sum_frame>(a, b); decltype(auto) returnObject release())); return returnObject; } template struct task; task sum(int a, int b) { int result = a + b; co_return result; } task sum4(int a, int b, int c, int d) { int ab = co_await

. . . . . . . . . . . 311 23 Parallel Computing 313 24 Asynchronous Programming 314 24.1 Basic Task operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 24.2 Communicating Communicating with Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 24.3 More task operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 24.4 Tasks and events Caveats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 25.8 Task Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 25.9 Safe

. . . . . . . . . . . 311 23 Parallel Computing 313 24 Asynchronous Programming 314 24.1 Basic Task operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 24.2 Communicating Communicating with Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 24.3 More task operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 24.4 Tasks and events Caveats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 25.8 Task Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 25.9 Safe

. . . . . . . . . . . 311 23 Parallel Computing 313 24 Asynchronous Programming 314 24.1 Basic Task operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 24.2 Communicating Communicating with Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 24.3 More task operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 24.4 Tasks and events Caveats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 25.8 Task Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 25.9 Safe

. . . . . . . . . . . 311 23 Parallel Computing 313 24 Asynchronous Programming 314 24.1 Basic Task operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 24.2 Communicating Communicating with Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 24.3 More task operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319CONTENTS v 24.4 Tasks Caveats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 25.8 Task Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 25.9 Safe