thread lock object.

[ajikoe@gmail.com]

Hello,

I have multi thread program running together and each will increment
int i.

How can we make only one thread at a time be able to access and
increment i ?

Thanks in advance,

Sincerely Yours,
pujo

[Irmen de Jong]

Re: thread lock object.

ajikoe@gmail.co m wrote:[color=blue]
> Hello,
>
> I have multi thread program running together and each will increment
> int i.
>
> How can we make only one thread at a time be able to access and
> increment i ?
>
> Thanks in advance,
>
> Sincerely Yours,
> pujo
>[/color]

Use a synchronization primitive such as a lock
(threading.Lock , threading.RLock )

But for simply incrementing a number (i+=1) this is not needed
because that operation cannot be interrupted by another thread,
as far as I know.

--Irmen

[ajikoe@gmail.com]

Re: thread lock object.

thanks.

Pujo

[Peter Hansen]

Re: thread lock object.

Irmen de Jong wrote:[color=blue]
> ajikoe@gmail.co m wrote:[color=green]
>> How can we make only one thread at a time be able to access and
>> increment i ?[/color]
>
> Use a synchronization primitive such as a lock
> (threading.Lock , threading.RLock )
>
> But for simply incrementing a number (i+=1) this is not needed
> because that operation cannot be interrupted by another thread,
> as far as I know.[/color]

Most assuredly it can:
[color=blue][color=green][color=darkred]
>>> def f():[/color][/color][/color]
.... global x
.... x += 1
....[color=blue][color=green][color=darkred]
>>> dis.dis(f)[/color][/color][/color]
3 0 LOAD_GLOBAL 0 (x)
3 LOAD_CONST 1 (1)
6 INPLACE_ADD
....a context-change here can lead to incorrect results...
7 STORE_GLOBAL 0 (x)
10 LOAD_CONST 0 (None)
13 RETURN_VALUE

-Peter