Re: Interlocked.Increment ?

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From: George Ter-Saakov (nospam_at_hotmail.com)
Date: 02/03/04 

Date: Tue, 3 Feb 2004 07:52:09 -0500

My understanding is that volatile word needs to be specified so compiler
will know not to optimize access to it.

Basically following code

i = 6;
k = i*8;
will give a result 48 even if i was changed in another thread.
Because compiler will figure out that i is not changed and it can safely
assign k a 48 in runtime.

volatile i = 6;
k = i*8;
Will not be optimized since compiler will know that i could have been
changed.

And in my opinion the variable used in Interlocked.Increment must be
declared as volatile since it's definitely will be changed in different
threads.

George.

"Felix Wu [MSFT]" <felixwu@online.microsoft.com> wrote in message
news:nK6RrKg6DHA.1992@cpmsftngxa07.phx.gbl...
> Hi George,
>
> InterLocked .Increment is not targeted to be used with volatile modifier.
I
> think if you are using InterLocked class, you don't need to use volatile.
> The volatile modifier is usually used for a field that is accessed by
> multiple threads without using the lock statement to serialize access.
>
> According to C# Language Specification (10.4.3 Volatile fields), for
> non-volatile fields, optimization techniques that reorder instructions can
> lead to unexpected and unpredictable results in multi-threaded programs
> that access fields without synchronization such as that provided by the
> lock-statement. To avoid this problem, we can use volatile modifier to
> guarantee safe access to the field.
>
> You can use InterLocked class to serialize access to the field to make it
> thread safe.
>
> Regards,
>
> Felix Wu
> =============
> This posting is provided "AS IS" with no warranties, and confers no
rights.
>
>
> --------------------
> >From: "George Ter-Saakov" <nospam@hotmail.com>
> >Subject: Interlocked.Increment ?
> >Date: Mon, 2 Feb 2004 13:29:08 -0500
> >Lines: 17
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> >
> >What is the purpose of having Interlocked.Increment if it does not work
> with
> >variable declared as volatile.
> >
> >Here is my problem,
> > Interlocked.Increment increments the variable in thread safe manner.
> >But at the same time if i want to use variable that could be changed in
> >another thread i must use volatile (to prevent optimization).
> >
> >But then i can not use Interlocked.Increment.
> >So i do not see any benefits of having Interlocked.Increment because i
can
> >not think of any use of it.
> >
> >
> >Thanks.
> >George.
> >
> >
> >
>

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