microbenchmarks and a real-world application • Conclusion 26Synchronous/Asynchronous Mechanisms Boil the water Synchronous Asynchronous Wait Polling Callback Check Do your things Multitasking! 27Taro’s motivation behind Taro • We have presented the Taro C++ programming model - Synchronous and Asynchronous mechanisms • We have presented the Taro coroutine-aware scheduling algorithm • We have presented

clients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6.4 Asynchronous networking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 257 Index 259 iiiTornado Documentation, Release 6.5.1 Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed. By using non-blocking network I/O, Tornado wait() if __name__ == "__main__": asyncio.run(main()) This example does not use any of Tornado’s asynchronous features; for that see this simple chat room. 5Tornado Documentation, Release 6.5.1 6 Chapter

Tornado [https://www.tornadoweb.org] is a Python web framework and asynchronous networking library, originally developed at FriendFeed [https://en.wikipedia.org/wiki/FriendFeed]. By using non-blocking __name__ == "__main__": asyncio.run(main()) This example does not use any of Tornado’s asynchronous features; for that see this simple chat room [https://github.com/tornadoweb/tornado/tree/stable/demos/chat] typically run with only one thread per process. See the User’s guide for more on Tornado’s approach to asynchronous programming. While some support of WSGI is available in the tornado.wsgi module, it is not a

in “standalone” Asio & Boost.Asio (P0958) 2async_wait_then_write 3Composed Asynchronous Operations Composing asynchronous operations enables the layered construction of operations whose power increases composed asynchronous operations from concrete types Customization points defer decisions to the consumer rather than the author making them arbitrarily 4async_wait_then_write 5Asynchronous Operations Operations Asynchronous operations are “atomic” pieces of asynchronous functionality Composing asynchronous operations presupposes asynchronous operations to compose Guarantees of composed asynchronous operations

protection duration (e.g., the user-defined fn is allowed to block or take long time) Asynchronous Reclamation • Asynchronous reclamation is invoked when the number of retired objects reaches some threshold: Michael Folly open-source library: github.com/facebook/folly under synchronization/Hazptr.h Is Asynchronous Reclamation Always Enough? delete ptr shutdown_resource_X() Hazard Pointer Synchronous Reclamation reclamation ~Foo() { use_resource_X (); } Foo* ptr = new Foo; Remove ptr Is Asynchronous Reclamation Always Enough? No Asynchronous reclamation: delete ptr Using unavailable resource X Hazard Pointer Synchronous

Contain its own logic ○ Asynchronous execution ○ Recurrening execution ○ Accesses its own data (user defined ingress) ○ Guaranteed single threaded execution ○ Supports optional asynchronous destruction logic Contain its own logic ○ Asynchronous execution ○ Recurrening execution ○ Accesses its own data (user defined ingress) ○ Guaranteed single threaded execution ○ Supports optional asynchronous destruction logicBasic is invoked it is also ‘de-scheduled’ and its signal is resetWork Contract asynchronous ‘destructor’Work Contract: Asynchronous Destruction 10 8 // create a work contract group work_contract_group workContractGroup(4);

Use object Remove object Retire object Reclaim object Unprotect object < 1 ns amortized asynchronous ~ 0 nstemplate > class hazard_pointer_obj_base { for extending C++26: ● Protection Counting (can be a topic for a future talk) ● Execution of Asynchronous Reclamation Proposed standard extensions: ● Synchronous reclamation ● Batch creation and destruction (wg21.link/p3135r1)Hazard Pointer Execution of Asynchronous ReclamationPossible inline asynchronous reclamation Hazard Pointer Execution of Asynchronous Reclamation void worker() { /* ... */ obj->retire();

PGAS - Asynchronous - RDMA operations executed by NIC - Allows irregular, one-sided access - Maps well to data structure ops CPU NIC CPU NIC DRAM DRAMAdvantages of PGAS - Asynchronous - RDMA PGAS - Asynchronous - RDMA operations executed by NIC - Allows irregular, one-sided access - Maps well to data structure ops CPU NIC CPU NIC DRAM DRAMAdvantages of PGAS - Asynchronous - RDMA PGAS - Asynchronous - RDMA operations executed by NIC - Allows irregular, one-sided access - Maps well to data structure ops CPU NIC CPU NIC DRAM DRAMAdvantages of PGAS - Asynchronous - RDMA

terminate (*) • Asynchronous tasks (C++11 async) – Uncaught exception in task gets captured – Waiting on result throws passed-along exception • P0443 executors + P1897 asynchronous algorithms – Separate body ➔ terminate • Asynchronous tasks (C++11 async) – Uncaught exception in task gets captured – Waiting on result throws passed-along exception • P0443 executors + P1897 asynchronous algorithms – Separate body ➔ terminate • Asynchronous tasks (C++11 async) – Uncaught exception in task gets captured – Waiting on result throws passed-along exception • P0443 executors + P1897 asynchronous algorithms – Separate

std::mdspan are blocking the arms need to operate asynchronously 104github.com/griswaldbrooks/spanny2 asynchronous dual arm control template struct bin_checker_t { using element_type = t accessor::reference can be any type doesn’t have to be a & or *github.com/griswaldbrooks/spanny2 asynchronous dual arm control template struct bin_checker_async_t { using element_type accessor::reference can be any type doesn’t have to be a & or *github.com/griswaldbrooks/spanny2 asynchronous dual arm control struct arbiter_dual_async { using result_type = std::expected;