CODEWITHSUNDEEP
synchronizationgogoroutine
Fabien
Fabien

Reputation: 13406

What is go's preferred way to synchronize goroutines

I have an expensive function that I apply on all items of a slice. I'm using goroutines to deal with that, each goroutine dealing with one item of the slice.

func Huge(lst []foo) {
  for _, item := range lst {
     go performSlow(item)
  }

  // How do I synchronize here ?
  return someValue(lst)
}

The question is, as shown in the comment, what is the preferred way to wait all goroutines have done their job before calling the someValue function ? Passing on a channel to performSlow and waiting until everyone has written on it works, but it seems overkill :

func Huge(lst []foo) {
  ch := make(chan bool)

  for _, item := range lst {
     go performSlow(item, ch)  // performSlow does its job, then writes a dummy value to ch
  }

  for i := range lst {
     _ = <-ch
  }

  return someValue(lst)
}

Is there a better (i.e. more efficient and/or more idiomatic) way to do it ?

Upvotes: 6

Views: 1221

Answers (1)

andybalholm
andybalholm

Reputation: 16100

Use sync.WaitGroup (http://godoc.org/sync#WaitGroup)

func Huge(lst []foo) {
  var wg sync.WaitGroup
  for _, item := range lst {
     wg.Add(1)
     go func() {
         performSlow(item)
         wg.Done()
     }()
  }

  wg.Wait()
  return someValue(lst)
}

Upvotes: 12

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