并发是让两个任务在不同的线程上并行运行。然而,异步方法在同一个线程上并行运行。这是如何实现的?还有,并行性呢?
这三个概念有什么不同?
并发是让两个任务在不同的线程上并行运行。然而,异步方法在同一个线程上并行运行。这是如何实现的?还有,并行性呢?
这三个概念有什么不同?
当前回答
并发+并行都意味着同时运行多个任务。我看到一些人认为这是有区别的,但这取决于你咨询的参考文献,没有真正的正确或错误的答案。
Asynchronous: In some communities this means non-blocking code, which can mean two things: It almost always means it will not block an OS thread. However, non-blocking can optionally mean that the next line of source code in a function will continue to run without delay. In Python await asyncio.sleep(5) blocks execution of the function, but not the OS thread, and that is considered async. In Golang, you have "goroutines" that similarly to Python's await, they block execution of code, but not OS threads, however, this is not referred to as async in the Golang community. It's just concurrent programming.
其他回答
并发与并行: 并发在一个时间点上只能完成一个任务。例如:单CPU处理器 并行性在一个点上我们可以做多个任务。例如:双核或多核处理器
我会让它简短而有趣,让你们能够理解这些概念。
并发与并行——任务执行的方式。
Take an example in real life: There’s a challenge that requires you to both eat a whole huge cake and sing a whole song. You’ll win if you’re the fastest who sings the whole song and finishes the cake. So the rule is that you sing and eat concurrently. How you do that does not belong to the rule. You can eat the whole cake, then sing the whole song, or you can eat half a cake, then sing half a song, then do that again, etc. Parallelism is a specific kind of concurrency where tasks are really executed simultaneously. In computer science, parallelism can only be achieved in multicore environments.
同步与异步——编程模型。
在同步中,您将代码编写为按顺序从上到下执行的步骤 底部。在异步编程模型中,你将代码作为任务编写, 然后并发执行。并发执行意味着 所有的任务都可能同时执行。
用类比来解释这些术语。
你的房子需要洗碗和洗衣服。
并发性:你不需要等完成一个任务后再启动另一个。例如,你可以先洗碗,也可以同时洗碗。他们可以按照任何顺序完成,也就是说,即使你先洗碗,也可能会先洗衣服。
平行性:你的房子里有不止一个人在做这件事;例如,你可以洗碗,而另一个人可以洗衣服。
异步:你让别人去洗衣服,你让别人去洗碗。他们实际上可以是同一个人(也就是说,你告诉他们去洗衣服,同时也告诉他们去洗碗)。他们处理完每个人后会向你报告。
同步:你叫别人去洗碗。你等着他们。当他们完成后,你可以做其他的事情(你可以告诉他们接下来洗衣服,或者你自己洗,或者你可以完全做其他的事情;重点是你在完成第一个任务时被阻塞,你与他们是同步的)。
“同步和异步是编程模型。并发和并行是任务执行的方式……” 来源:https://medium.com/better - programming/sync vs -异步并发- vs - vs - 5754 cdb60f66平行
换句话说,同步和异步描述了在进行函数调用时程序如何执行(它是等待还是继续执行?),而并发和并行描述了函数(任务)将如何执行(并发=可能同时执行,并行=有效地同时执行)。
并发+并行都意味着同时运行多个任务。我看到一些人认为这是有区别的,但这取决于你咨询的参考文献,没有真正的正确或错误的答案。
Asynchronous: In some communities this means non-blocking code, which can mean two things: It almost always means it will not block an OS thread. However, non-blocking can optionally mean that the next line of source code in a function will continue to run without delay. In Python await asyncio.sleep(5) blocks execution of the function, but not the OS thread, and that is considered async. In Golang, you have "goroutines" that similarly to Python's await, they block execution of code, but not OS threads, however, this is not referred to as async in the Golang community. It's just concurrent programming.