… … Stack Traces for Async Code are Unhelpful Threadpool threads: #0 process_file(...) #5 pool.run() #10 __clone … … IO Thread: #0 async_read_some_at(...) #3 ctx Threadpool threads: #0 process_file(...) #5 pool.run() #10 … IO Thread: … #0 async_read_some_at(...) #3 ctx.run() #5 __clone … … Main thread: #0 unifex::sync_wait( … #0 async_read_some_at(...) … #12 unifex::sync_wait(...) #16 main() #19 __libc_start_main() … … Async Stacks are BetterStructured Concurrency Makes Async Stacks Possible

Intended solely for use on private network Client (front-end) sends request Server (back-end) accepts or rejects Response streamed until final message or until client requests cancel Server acknowledges cancel Message type ... Body (optional) 6 DataConn Messages (Client to Server) Type Name Payload? R Request ✓ C Cancel 7 DataConn Messages (Server to Client) Type Name Payload? Terminal? A Acknowledge Request template decltype(auto) async_read(AsyncReadStream& stream, DynamicBufferV2 buffer, CompletionToken&& token); 9 Dynamic Buffer

happening. 30Session? • Can we describe a valid sequence of interactions? • Interaction diagram Client Server int int ADD DIV int double end Branching 31Session? • Can we describe a valid sequence operation is allowed!) • Then, again receive int • ... ?int; ?int; &(ADD: !int, DIV: !double); end Client Server int int ADD DIV int double end *Name “Behavioral types” is also used. See “Behavioral actors Two main cases in practice • concurrent queues • networking sockets Bounded/Unbounded, Sync/Async, MPMC, MPSC, SPMC, SPSC, Lockfree, Blocking... 52Communication? • Abstraction: channels... or actors

● Robotics Engineer on the services team at PickNik Robotics ○ Contributed to a wide variety of client projects: remotely operated underwater inspection vehicles, autonomous mobile base for agriculture maintain, and extend ● At the end of a services project, code is handed over to the client ● How can the client expect proper operation of the software once they start developing on top of it?Why give maintain, and extend ● At the end of a services project, code is handed over to the client ● How can the client expect proper operation of the software once they start developing on top of it? Answer:

std::vector dA{ … }, dB{ … }, dO{ … }; try { sycl::queue gpuQueue{sycl::gpu_selector_v, async_handler{}}; sycl::buffer bufA{dA.data(), sycl::range{dA.size()}}; sycl::buffer bufB{dB std::vector dA{ … }, dB{ … }, dO{ … }; try { sycl::queue gpuQueue{sycl::gpu_selector_v, async_handler{}}; sycl::buffer bufA{dA.data(), sycl::range{dA.size()}}; sycl::buffer bufB{dB std::vector dA{ … }, dB{ … }, dO{ … }; try { sycl::queue gpuQueue{sycl::gpu_selector_v, async_handler{}}; sycl::buffer bufA{dA.data(), sycl::range{dA.size()}}; sycl::buffer bufB{dB

work off the current thread? Many environments have a dedicated thread for processing events: GUIs Client-Server applications Performing extensive processing on the event thread prevents other events from std::jthread std::async(std::launch::async,...) Platform-specific APIsSpawning new threads There are lots of ways to spawn new threads: std::thread std::jthread std::async(std::launch::async,...) Platform-specific II std::async is a bit better: we can check the std::future to see if it is ready. std::vector> pending_threads; void handle_event(Event details){ auto handle=std::async( std::launch::async

for network and timer events. • It uses an async_scope for outstanding work. • Initial work consist of accepting incoming client connections. • Each client processes requests until an error is received networking: http://wg21.link/p2762 • Implementation: https://github.com/beman-project/net29 • Async scope: http://wg21.link/p3149 Resources

analysis! Don't generalize from single use case 21CUSTOMIZING GENERIC FUNCTIONS Client code → generic library code → client code 221. DISPATCH TO FUNCTION OVERLOADS void place_items(rect bounds, forward_range redirected_process : base { redirected_process& operator<<(std::string const& s) }; 1 2 3 4 5 struct async_base { 6 void write(std::string const& s); 7 }; 8 9 struct sync_base { 10 void write(std::string s) }; 1 2 3 4 5 struct async_base { 6 void write(std::string const& s); 7 }; 8 9 struct sync_base { 10 void write(std::string const& s); 11 }; 12 struct async_base { void write(std::string

future is a non-mutable placeholder for a value, which is set by a promise. auto future = std::async([]{ return "LazyOrEager"; }); future.get(); Future: receiver get Promise: sender set channelConcurrency ▪ It runs in the client thread. Method Request ▪ Includes all context information to be executed later. Activation List: ▪ Has the pending requests objects. ▪ Decouples the client from the Active returns a result. ▪ The client uses the future to get the result of the request object.Active Object Dynamic Behavior 1. Request construction and scheduling: ▪ The client invokes the method on the

has dangling accessor */ }); ▪ submit is an async action ▪ Lambda copies accessor a into that action ▪ Keeps the accessor alive until the end of the async operation ▪ After parallel_for returns, buffer com/intel/llvm Open to all! https://community.khronos.org/www.khr.io/slack https://app.slack.com/client/TDMDFS87M/CE9UX4CHG https://community.khronos.org/c/sycl/ https://stackoverflow.com/questions/tagged/sycl