channel | 易学教程

Explain: Don't communicate by sharing memory; share memory by communicating

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问题 I wonder what is the most down to earth explanation of this famous quote: Don't communicate by sharing memory; share memory by communicating. (R. Pike) In The Go Memory Model I can read this: A send on a channel happens before the corresponding receive from that channel completes. (Golang Spec) There is also a dedicated golang article explaining the quote. And key contribution is a working example also by Andrew G. Well. Sometimes too much talking around .... I have derived from the Memory

How to control the MIDI channel's volume

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问题 I have this code: Synthesizer synthesizer = MidiSystem.getSynthesizer(); synthesizer.open(); Instrument[] instrument = synthesizer.getDefaultSoundbank().getInstruments(); synthesizer.loadInstrument(instrument[29]); MidiChannel[] channels = synthesizer.getChannels(); MidiChannel channel = channels[1]; channel.programChange(29); channel.noteOn(noteNumber, 127); Teszthang.sleep(2000); channel.noteOff(noteNumber); so this is an example, to play a sound in max volume (127) for 2 seconds. but i

Solving goroutines deadlock

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问题 I've been trying to solve this simple problem I encountered in Golang concurrency. I've been searching all possible solutions, but found nothing specific to my problem(or I might be missed one). Here's my code: package main import ( "fmt" "time" ) func producer(ch chan int, d time.Duration, num int) { for i:=0; i<num; i++ { ch <- i time.Sleep(d) } } func main() { ch := make(chan int) go producer(ch, 100*time.Millisecond, 2) go producer(ch, 200*time.Millisecond, 5) for { fmt.Println(<-ch) }

Closing channel of unknown length

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问题 I'm not able to close channel when there is no knowledge about its length package main import ( "fmt" "time" ) func gen(ch chan int) { var i int for { time.Sleep(time.Millisecond * 10) ch <- i i++ // when no more data (e.g. from db, or event stream) if i > 100 { break } } // hot to close it properly? close(ch) } func receiver(ch chan int) { for i := range ch { fmt.Println("received:", i) } } func main() { ch := make(chan int) for i := 0; i < 10; i++ { go gen(ch) } receiver(ch) } It gives me

RabbitMQ by Example: Multiple Threads, Channels and Queues

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问题 I just read RabbitMQ's Java API docs, and found it very informative and straight-forward. The example for how to set up a simple Channel for publishing/consuming is very easy to follow and understand. But it's a very simple/basic example, and it left me with an important question: How can I set up 1+ Channels to publish/consume to and from multiple queues? Let's say I have a RabbitMQ server with 3 queues on it: logging , security_events and customer_orders . So we'd either need a single

Golang timeout is not executed with channels

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问题 I am using goroutines/channels. Here is my code. Why is the timeout case not getting executed? func main() { c1 := make(chan int, 1) go func() { for { time.Sleep(1500 * time.Millisecond) c1 <- 10 } }() go func() { for { select { case i := <-c1: fmt.Println(i) case <-time.After(2000 * time.Millisecond): fmt.Println("TIMEOUT") // <-- Not Executed } } }() fmt.Scanln() } 回答1: Your timeout doesn't happen, because one of your goroutine sends a value on your c1 channel in every 1.5 seconds (or so)

Golang timeout is not executed with channels

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[高并发Java 八] NIO和AIO

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> IO感觉上和多线程并没有多大关系，但是NIO改变了线程在应用层面使用的方式，也解决了一些实际的困难。而AIO是异步IO和前面的系列也有点关系。在此，为了学习和记录，也写一篇文章来介绍NIO和AIO。 1. 什么是NIO NIO是New I/O的简称，与旧式的基于流的I/O方法相对，从名字看，它表示新的一套Java I/O标准。它是在Java 1.4中被纳入到JDK中的，并具有以下特性： NIO是基于块（Block）的，它以块为基本单位处理数据（硬盘上存储的单位也是按Block来存储，这样性能上比基于流的方式要好一些）为所有的原始类型提供（Buffer）缓存支持增加通道（Channel）对象，作为新的原始 I/O 抽象支持锁（我们在平时使用时经常能看到会出现一些.lock的文件，这说明有线程正在使用这把锁，当线程释放锁时，会把这个文件删除掉，这样其他线程才能继续拿到这把锁）和内存映射文件的文件访问接口提供了基于Selector的异步网络I/O 所有的从通道中的读写操作，都要经过Buffer，而通道就是io的抽象，通道的另一端就是操纵的文件。 2. Buffer Java中Buffer的实现。基本的数据类型都有它对应的Buffer Buffer的简单使用例子： package test; import

PackagesNotFoundError: The following packages are not available from current channels:

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问题 I'm somewhat new to Python. I've used it in a bunch of projects, but haven't really needed to stray from its standard setup. I'm trying to install some new packages to get access to functions necessary for a university assignment. When I try to install, I get the following: (base) C:\Anaconda2\Jupyter>conda install -c python-control -c cyclus slycot control Solving environment: failed PackagesNotFoundError: The following packages are not available from current channels: - slycot - control

What are channels used for?

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问题 When looking through some Go code I found the following: ch := make(chan int) I looked up in a online tutorial how Go Channels work: https://tour.golang.org/concurrency/2 But I find this example unclear. Can someone give me a easy explanation and an example of the use of channels? 回答1: chan is a channel in Golang. In simple word you can think it as a box in which you put a item at one end and then pick it from other end. Unbuffered Channels Buffered Channel This is the small code I have