在下面的代码中：
package main
import (
"fmt"
"runtime"
)
// pooling: You are a manager and you hire a team of employees. None of the new
// employees know what they are expected to do and wait for you to provide work.
// When work is provided to the group, any given employee can take it and you
// don't care who it is. The amount of time you wait for any given employee to
// take your work is unknown because you need a guarantee that the work your
// sending is received by an employee.
func pooling() {
jobCh := make(chan int) // signalling data with guarantee - unbuffered
resultCh := make(chan int) // signalling data with guarantee - unbuffered
workers := runtime.NumCPU() // 4 workers
for worker := 0; worker < workers; worker++ {
go func(emp int) {
var p int
for p = range jobCh {
fmt.Printf("employee %d : recv'd signal : %d\n", emp, p) // do the work
}
fmt.Printf("employee %d : recv'd shutdown signal\n", emp) // worker is signaled with closed state channel
resultCh <- p * 2
}(worker)
}
const jobs = 6
for jobNum := 1; jobNum <= jobs; jobNum++ {
jobCh <- jobNum
fmt.Println("manager : sent signal :", jobNum)
}
close(jobCh)
fmt.Println("manager : sent shutdown signal")
for a := 1; a <= jobs; a++ { //cannot range on 'resultCh'
fmt.Println("Result received: ", <-resultCh)
}
fmt.Println("-------------------------------------------------------------")
}
func main() {
pooling()
}
manager(pooling()) is not receiving all six results, from 4 workers(employees), as shown below:
$ uname -a
Linux user 4.15.0-99-generic #100-Ubuntu SMP Wed Apr 22 20:32:56 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
$
$ go version
go version go1.14.1 linux/amd64
$
$ go install github.com/myhub/cs61a
$
$
$ bin/cs61a
manager : sent signal : 1
manager : sent signal : 2
manager : sent signal : 3
employee 3 : recv'd signal : 3
employee 3 : recv'd signal : 4
manager : sent signal : 4
manager : sent signal : 5
employee 3 : recv'd signal : 5
employee 3 : recv'd signal : 6
manager : sent signal : 6
manager : sent shutdown signal
employee 3 : recv'd shutdown signal
employee 2 : recv'd signal : 2
Result received: 12
employee 0 : recv'd signal : 1
employee 0 : recv'd shutdown signal
employee 2 : recv'd shutdown signal
Result received: 2
Result received: 4
employee 1 : recv'd shutdown signal
Result received: 0
fatal error: all goroutines are asleep - deadlock!
goroutine 1 [chan receive]:
main.pooling()
/home/../src/github.com/myhub/cs61a/Main.go:40 +0x25f
main.main()
/home/../src/github.com/myhub/cs61a/Main.go:45 +0x20
$
$
$ bin/cs61a
manager : sent signal : 1
employee 0 : recv'd signal : 1
manager : sent signal : 2
manager : sent signal : 3
manager : sent signal : 4
employee 3 : recv'd signal : 2
manager : sent signal : 5
manager : sent signal : 6
employee 2 : recv'd signal : 4
employee 2 : recv'd shutdown signal
employee 0 : recv'd signal : 5
manager : sent shutdown signal
Result received: 8
employee 0 : recv'd shutdown signal
Result received: 10
employee 1 : recv'd signal : 3
employee 1 : recv'd shutdown signal
Result received: 6
employee 3 : recv'd signal : 6
employee 3 : recv'd shutdown signal
Result received: 12
fatal error: all goroutines are asleep - deadlock!
goroutine 1 [chan receive]:
main.pooling()
/home/user/../github.com/myhub/cs61a/Main.go:40 +0x25f
main.main()
/home/user/../github.com/myhub/cs61a/Main.go:45 +0x20
1) Why pooling() is not able to receive results from all workers?
2)
manager is receiving only 4 results out of 6. One of the result received is zero(Result received: 0), data sent on resultCh is always supposed to be non-zero, Why resultCh receives zero value? looks like resultCh is closed....
Note: Correct working of resultCh is not part of the responsibility of worker pool pattern. Worker pool pattern only ensure the work is submitted to employee successfully using jobCh
