Twitter @GerardoLijs C# MeetUp Barcelona April 2019 Content What is Asynchronous Programming CPU-bound vs IO-bound Obsolete patterns Tasks and async/await Practical use cases • Responsive user interfaces • Scalability and performance in web applications @GerardoLijs CPU-bound operations • Use Task.Run to execute expensive CPU-bound code in the ThreadPool • Define a Task returning method • In general the time you will need asynchronous to deal with IO-bound operations and the times you will use CPU-bound operations you will probably use a library that provides asynchronous methods for you to interact

p 课程 PPT 和代码： https://github.com/parallel101/course 为什么往 int 数组里赋值 1 比赋值 0 慢一倍？ 第 1 章：内存带宽 cpu-bound 与 memory-bound • 通常来说，并行只能加速计算的部分，不能加速内存读写的部分 。 • 因此，对 fill 这种没有任何计算量，纯粹只有访存的循环体，并 行没有加速效果。称为内存瓶颈（ • 因为局部数组的大小远远小于一级缓存，这样迭代时 读写的带宽就是一级缓存的速度，几乎没有影响。 • 这里一次循环体直接相当于 16 次迭代，两次就完了。 但是可能加的有点过头变成 cpu-bound 了，所以只快 了 10 倍左右，大家掌握里面的思想就好。 进一步优化 • 用了一些常量作为参数，调整一下局部数组的大小。 • 加速比： 16 倍，大概已经到极限了？ 进亿步优化 •

“provides an asynchronous, evented and/or continuation passing style API for moving blocking/longish CPU-bound tasks out of Node's event loop to JavaScript threads that run in parallel in the background and

ProcessPoolExecutor is another alternative for long running tasks that do not release the GIL, such as CPU-bound pure Python code. Note, however, that ProcessPoolExecutor builds upon the multiprocessing mod- ule AbstractEventLoop.set_default_executor() is used to change it to something else. Due to the GIL, CPU-bound jobs will block request processing for the current process unless the default Executor is changed Warning: This helper is only to be used for functions that do not perform any blocking I/O or lengthy CPU-bound operations, since the entire async loop will be blocked while the wrapped function is executed.

ProcessPoolExecutor is another alternative for long running tasks that do not release the GIL, such as CPU-bound pure Python code. Note, however, that ProcessPoolExecutor builds upon the multiprocessing mod- ule AbstractEventLoop.set_default_executor() is used to change it to something else. Due to the GIL, CPU-bound jobs will block request processing for the current process unless the default Executor is changed Warning: This helper is only to be used for functions that do not perform any blocking I/O or lengthy CPU-bound operations, since the entire async loop will be blocked while the wrapped function is executed.

ProcessPoolExecutor is another alternative for long running tasks that do not release the GIL, such as CPU-bound pure Python code. Note, however, that ProcessPoolExecutor builds upon the multiprocessing mod- ule AbstractEventLoop.set_default_executor() is used to change it to something else. Due to the GIL, CPU-bound jobs will block request processing for the current process unless the default Executor is changed Warning: This helper is only to be used for functions that do not perform any blocking I/O or lengthy CPU-bound operations, since the entire async loop will be blocked while the wrapped function is executed.

ProcessPoolExecutor is another alternative for long running tasks that do not release the GIL, such as CPU-bound pure Python code. Note, however, that ProcessPoolExecutor builds upon the multiprocessing mod- ule AbstractEventLoop.set_default_executor() is used to change it to something else. Due to the GIL, CPU-bound jobs will block request processing for the current process unless the default Executor is changed Warning: This helper is only to be used for functions that do not perform any blocking I/O or lengthy CPU-bound operations, since the entire async loop will be blocked while the wrapped function is executed.

ProcessPoolExecutor is another alternative for long running tasks that do not release the GIL, such as CPU-bound pure Python code. Note, however, that ProcessPoolExecutor builds upon the multiprocessing mod- ule AbstractEventLoop.set_default_executor() is used to change it to something else. Due to the GIL, CPU-bound jobs will block request processing for the current process unless the default Executor is changed Warning: This helper is only to be used for functions that do not perform any blocking I/O or lengthy CPU-bound operations, since the entire async loop will be blocked while the wrapped function is executed.

ProcessPoolExecutor is another alternative for long running tasks that do not release the GIL, such as CPU-bound pure Python code. Note, however, that ProcessPoolExecutor builds upon the multiprocessing mod- ule AbstractEventLoop.set_default_executor() is used to change it to something else. Due to the GIL, CPU-bound jobs will block request processing for the current process unless the default Executor is changed Warning: This helper is only to be used for functions that do not perform any blocking I/O or lengthy CPU-bound operations, since the entire async loop will be blocked while the wrapped function is executed.

ProcessPoolExecutor] is another alternative for long running tasks that do not release the GIL, such as CPU-bound pure Python code. Note, however, that ProcessPoolExecutor [https://docs.python.org/3/library/concurrent AbstractEventLoop.set_default_executor() is used to change it to something else. Due to the GIL, CPU-bound jobs will block request processing for the current process unless the default Executor [https://docs Warning This helper is only to be used for functions that do not perform any blocking I/O or lengthy CPU-bound operations, since the entire async loop will be blocked while the wrapped function is executed.