Metered concurrency: Difference between revisions
→Buffered channel: clarity
(→Go, Buffered channel: small improvement to code, more explanation.) |
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=={{header|Go}}==
===Buffered channel===
Recommended solution for simplicity. Acquire operation is channel send, release is channel receive, and count is provided with cap and len
To demonstrate, this example implements the [https://en.wikipedia.org/wiki/Semaphore_(programming)#Library_analogy Library analogy] from Wikipedia with 10 study rooms and 20 students.
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"time"
)
// counting semaphore implemented with a buffered channel
type sem chan struct{}
func (s sem) release() { <-s }
func (s sem) count() int { return cap(s) - len(s) }
// log package serializes output
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func main() {
▲ rooms := make(chan struct{}, nRooms)
▲ rooms <- struct{}{}
// WaitGroup used to wait for all students to have studied
// before terminating program
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}
func student(rooms
// report per task descrption. also exercise count operation
fmt.Printf("Room entered. Count is %d. Studying...\n",
time.Sleep(2 * time.Second) // sleep per task description
rooms
studied.Done()
}</lang>
Output for this and the other Go programs here shows 10 students studying immediately, about a 2 second pause, 10 more students studying, then another pause of about 2 seconds before returning to the command prompt. In this example the count values may look jumbled. This is a result of the student goroutines running concurrently.
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