Re: [go-nuts] Re: concurrency programing about go
Indeed this is what I do but I learned the hard way and often it comes up
as "safe" in the mailing list to not do so but while true from a memory
model perspective it is, I would say, wrong to do so.
mån 6 nov. 2017 kl 10:39 skrev Christoph Berger <
christoph.g.ber...@gmail.com>:
> Always call Add() before spawning the corresponding goroutine(s). And
> always call Add() in the same goroutine that also calls Wait(). This way
> you have no race condition between Add(), Done(), and Wait().
>
>
> On Saturday, November 4, 2017 at 10:46:21 AM UTC+1, Henrik Johansson wrote:
>
>> I find continuously adding and calling done on a waitgroup a bit odd. The
>> waiting goroutine can continue as soon as the count is zero so there is a
>> race between adds and dones.
>>
>> On Sat, 4 Nov 2017, 10:01 , <28911...@gmail.com> wrote:
>>
> Thank you very much.Sorry I still have some question:what's the function
>>> of wg? what does the sentense "wg.Add(2) " mean?? I found that if I change
>>> 2 into 1,the result is differnet.
>>>
>>> 在 2017年11月3日星期五 UTC+8上午4:45:47，snmed写道：
>>>
Hi
Here is the code:
Version 1:
package main
import (
"fmt"
"sync"
)
var a string
var once sync.Once
func setup() {
a = "hello,world\n"
}
func doprint() {
once.Do(setup)
fmt.Print(a)
}
func twoprint() <-chan struct{} {
var wg sync.WaitGroup
wg.Add(2)
ch := make(chan struct{})
go func() {
doprint()
wg.Done()
}()
go func() {
doprint()
wg.Done()
}()
go func() {
wg.Wait()
close(ch)
}()
return ch
}
func main() {
ch := twoprint()
<-ch
}
Version 2:
package main
import (
"fmt"
"sync"
)
var a string
var once sync.Once
func setup() {
a = "hello,world\n"
}
func doprint() {
once.Do(setup)
fmt.Print(a)
}
func twoprint() {
var wg sync.WaitGroup
wg.Add(2)
go func() {
doprint()
wg.Done()
}()
go func() {
doprint()
wg.Done()
}()
wg.Wait()
}
func main() {
twoprint()
}
Cheers snmed
Am Donnerstag, 2. November 2017 10:37:15 UTC+1 schrieb
28911...@gmail.com:
>
> Sorry,I try my best to open the website but it can't work.Can you
> write it ??Thank you so much.
>
> 在 2017年10月30日星期一 UTC+8下午4:29:44，snmed写道：
>>
>> Hi
>>
>> There are several ways to solve it, here are two of them:
>>
>> https://play.golang.org/p/wJwkI7HQwv
>> https://play.golang.org/p/nasUcgBeG4
>>
>> I prefer the first one, because so I can decide if i want to wait for
>> the end of twoprint or not.
>>
>> Cheers
>>
>> Am Montag, 30. Oktober 2017 06:43:45 UTC+1 schrieb 28911...@gmail.com
>> :
>>>
>>> Yes, you're right.So how to solve it??
>>>
>>> 在 2017年10月30日星期一 UTC+8下午12:37:49，Dave Cheney写道：
Hello. I’m guessing that your tried calling twoprint(), but you’ve
probably found that nothing is printed to the screen before your
program
exits.
Is that correct?
>>>
>>> --
>>> You received this message because you are subscribed to the Google
>>> Groups "golang-nuts" group.
>>>
>> To unsubscribe from this group and stop receiving emails from it, send an
>>> email to golang-nuts...@googlegroups.com.
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>>
>>> For more options, visit https://groups.google.com/d/optout.
>>>
>> --
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Re: [go-nuts] Re: concurrency programing about go
Just a note that waitGroup should be passed as reference to functions/methods rather than as value. I have made mistakes where the program hung as Done was called on copy of waitgroup rather than on the original wg to which tasks were added. Here it is not a problem as waitgroup used within anon functions is taken from scope. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [go-nuts] Re: concurrency programing about go
Always call Add() before spawning the corresponding goroutine(s). And
always call Add() in the same goroutine that also calls Wait(). This way
you have no race condition between Add(), Done(), and Wait().
On Saturday, November 4, 2017 at 10:46:21 AM UTC+1, Henrik Johansson wrote:
>
> I find continuously adding and calling done on a waitgroup a bit odd. The
> waiting goroutine can continue as soon as the count is zero so there is a
> race between adds and dones.
>
> On Sat, 4 Nov 2017, 10:01 , <28911...@gmail.com > wrote:
>
>> Thank you very much.Sorry I still have some question:what's the function
>> of wg? what does the sentense "wg.Add(2) " mean?? I found that if I change
>> 2 into 1,the result is differnet.
>>
>> 在 2017年11月3日星期五 UTC+8上午4:45:47，snmed写道：
>>
>>> Hi
>>>
>>> Here is the code:
>>>
>>> Version 1:
>>> package main
>>>
>>> import (
>>> "fmt"
>>> "sync"
>>> )
>>>
>>> var a string
>>> var once sync.Once
>>>
>>> func setup() {
>>> a = "hello,world\n"
>>> }
>>> func doprint() {
>>> once.Do(setup)
>>> fmt.Print(a)
>>> }
>>> func twoprint() <-chan struct{} {
>>> var wg sync.WaitGroup
>>> wg.Add(2)
>>> ch := make(chan struct{})
>>>
>>> go func() {
>>> doprint()
>>> wg.Done()
>>> }()
>>> go func() {
>>> doprint()
>>> wg.Done()
>>> }()
>>>
>>> go func() {
>>> wg.Wait()
>>> close(ch)
>>> }()
>>>
>>> return ch
>>> }
>>>
>>> func main() {
>>> ch := twoprint()
>>> <-ch
>>> }
>>>
>>>
>>> Version 2:
>>> package main
>>>
>>> import (
>>> "fmt"
>>> "sync"
>>> )
>>>
>>> var a string
>>> var once sync.Once
>>>
>>> func setup() {
>>> a = "hello,world\n"
>>> }
>>> func doprint() {
>>> once.Do(setup)
>>> fmt.Print(a)
>>> }
>>> func twoprint() {
>>> var wg sync.WaitGroup
>>> wg.Add(2)
>>>
>>> go func() {
>>> doprint()
>>> wg.Done()
>>> }()
>>> go func() {
>>> doprint()
>>> wg.Done()
>>> }()
>>>
>>> wg.Wait()
>>> }
>>>
>>> func main() {
>>> twoprint()
>>> }
>>>
>>>
>>> Cheers snmed
>>>
>>>
>>> Am Donnerstag, 2. November 2017 10:37:15 UTC+1 schrieb
>>> 28911...@gmail.com:
Sorry,I try my best to open the website but it can't work.Can you write
it ??Thank you so much.
在 2017年10月30日星期一 UTC+8下午4:29:44，snmed写道：
>
> Hi
>
> There are several ways to solve it, here are two of them:
>
> https://play.golang.org/p/wJwkI7HQwv
> https://play.golang.org/p/nasUcgBeG4
>
> I prefer the first one, because so I can decide if i want to wait for
> the end of twoprint or not.
>
> Cheers
>
> Am Montag, 30. Oktober 2017 06:43:45 UTC+1 schrieb 28911...@gmail.com:
>>
>> Yes, you're right.So how to solve it??
>>
>> 在 2017年10月30日星期一 UTC+8下午12:37:49，Dave Cheney写道：
>>>
>>> Hello. I’m guessing that your tried calling twoprint(), but you’ve
>>> probably found that nothing is printed to the screen before your
>>> program
>>> exits.
>>>
>>> Is that correct?
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "golang-nuts" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to golang-nuts...@googlegroups.com .
>> For more options, visit https://groups.google.com/d/optout.
>>
>
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RE: [go-nuts] Re: concurrency programing about go
If you were to do that, yes. I guess it come to: How do you define “done” in
your program? Waitgroup defines it as when all the goroutines which it counted
are closed.
John
John Souvestre - New Orleans LA
From: golang-nuts@googlegroups.com [mailto:golang-nuts@googlegroups.com] On
Behalf Of Henrik Johansson
Sent: 2017 November 04, Sat 04:46
To: 2891132l...@gmail.com
Cc: golang-nuts
Subject: Re: [go-nuts] Re: concurrency programing about go
I find continuously adding and calling done on a waitgroup a bit odd. The
waiting goroutine can continue as soon as the count is zero so there is a race
between adds and dones.
On Sat, 4 Nov 2017, 10:01 , <2891132l...@gmail.com> wrote:
Thank you very much.Sorry I still have some question:what's the function of wg?
what does the sentense "wg.Add(2) " mean?? I found that if I change 2 into
1,the result is differnet.
在 2017年11月3日星期五 UTC+8上午4:45:47，snmed写道：
Hi
Here is the code:
Version 1:
package main
import (
"fmt"
"sync"
)
var a string
var once sync.Once
func setup() {
a = "hello,world\n"
}
func doprint() {
once.Do(setup)
fmt.Print(a)
}
func twoprint() <-chan struct{} {
var wg sync.WaitGroup
wg.Add(2)
ch := make(chan struct{})
go func() {
doprint()
wg.Done()
}()
go func() {
doprint()
wg.Done()
}()
go func() {
wg.Wait()
close(ch)
}()
return ch
}
func main() {
ch := twoprint()
<-ch
}
Version 2:
package main
import (
"fmt"
"sync"
)
var a string
var once sync.Once
func setup() {
a = "hello,world\n"
}
func doprint() {
once.Do(setup)
fmt.Print(a)
}
func twoprint() {
var wg sync.WaitGroup
wg.Add(2)
go func() {
doprint()
wg.Done()
}()
go func() {
doprint()
wg.Done()
}()
wg.Wait()
}
func main() {
twoprint()
}
Cheers snmed
Am Donnerstag, 2. November 2017 10:37:15 UTC+1 schrieb 28911...@gmail.com:
Sorry,I try my best to open the website but it can't work.Can you write it
??Thank you so much.
在 2017年10月30日星期一 UTC+8下午4:29:44，snmed写道：
Hi
There are several ways to solve it, here are two of them:
https://play.golang.org/p/wJwkI7HQwv
https://play.golang.org/p/nasUcgBeG4
I prefer the first one, because so I can decide if i want to wait for the end
of twoprint or not.
Cheers
Am Montag, 30. Oktober 2017 06:43:45 UTC+1 schrieb 28911...@gmail.com:
Yes, you're right.So how to solve it??
在 2017年10月30日星期一 UTC+8下午12:37:49，Dave Cheney写道：
Hello. I’m guessing that your tried calling twoprint(), but you’ve probably
found that nothing is printed to the screen before your program exits.
Is that correct?
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
--
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To unsubscribe from this group and stop receiving emails from it, send an email
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For more options, visit https://groups.google.com/d/optout.
--
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For more options, visit https://groups.google.com/d/optout.
Re: [go-nuts] Re: concurrency programing about go
I find continuously adding and calling done on a waitgroup a bit odd. The
waiting goroutine can continue as soon as the count is zero so there is a
race between adds and dones.
On Sat, 4 Nov 2017, 10:01 , <2891132l...@gmail.com> wrote:
> Thank you very much.Sorry I still have some question:what's the function
> of wg? what does the sentense "wg.Add(2) " mean?? I found that if I change
> 2 into 1,the result is differnet.
>
> 在 2017年11月3日星期五 UTC+8上午4:45:47，snmed写道：
>
>> Hi
>>
>> Here is the code:
>>
>> Version 1:
>> package main
>>
>> import (
>> "fmt"
>> "sync"
>> )
>>
>> var a string
>> var once sync.Once
>>
>> func setup() {
>> a = "hello,world\n"
>> }
>> func doprint() {
>> once.Do(setup)
>> fmt.Print(a)
>> }
>> func twoprint() <-chan struct{} {
>> var wg sync.WaitGroup
>> wg.Add(2)
>> ch := make(chan struct{})
>>
>> go func() {
>> doprint()
>> wg.Done()
>> }()
>> go func() {
>> doprint()
>> wg.Done()
>> }()
>>
>> go func() {
>> wg.Wait()
>> close(ch)
>> }()
>>
>> return ch
>> }
>>
>> func main() {
>> ch := twoprint()
>> <-ch
>> }
>>
>>
>> Version 2:
>> package main
>>
>> import (
>> "fmt"
>> "sync"
>> )
>>
>> var a string
>> var once sync.Once
>>
>> func setup() {
>> a = "hello,world\n"
>> }
>> func doprint() {
>> once.Do(setup)
>> fmt.Print(a)
>> }
>> func twoprint() {
>> var wg sync.WaitGroup
>> wg.Add(2)
>>
>> go func() {
>> doprint()
>> wg.Done()
>> }()
>> go func() {
>> doprint()
>> wg.Done()
>> }()
>>
>> wg.Wait()
>> }
>>
>> func main() {
>> twoprint()
>> }
>>
>>
>> Cheers snmed
>>
>>
>> Am Donnerstag, 2. November 2017 10:37:15 UTC+1 schrieb 28911...@gmail.com
>> :
>>>
>>> Sorry,I try my best to open the website but it can't work.Can you write
>>> it ??Thank you so much.
>>>
>>> 在 2017年10月30日星期一 UTC+8下午4:29:44，snmed写道：
Hi
There are several ways to solve it, here are two of them:
https://play.golang.org/p/wJwkI7HQwv
https://play.golang.org/p/nasUcgBeG4
I prefer the first one, because so I can decide if i want to wait for
the end of twoprint or not.
Cheers
Am Montag, 30. Oktober 2017 06:43:45 UTC+1 schrieb 28911...@gmail.com:
>
> Yes, you're right.So how to solve it??
>
> 在 2017年10月30日星期一 UTC+8下午12:37:49，Dave Cheney写道：
>>
>> Hello. I’m guessing that your tried calling twoprint(), but you’ve
>> probably found that nothing is printed to the screen before your program
>> exits.
>>
>> Is that correct?
>
> --
> You received this message because you are subscribed to the Google Groups
> "golang-nuts" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to golang-nuts+unsubscr...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
>
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