Re: Multithreaded Programming

[Rich Duzenbury <rduz@xxxxxxxxxxxxxxxxxxx>]

How would you prevent two threads from updating a variable at the same time?

Regards,
Rich


At 12:30 PM 2/28/01 -0800, you wrote:
>Actually,
>
>I think building subroutines in a library with static variables would
>do the same thing as a shared named user space.
>
>Just a though.
>
>Regards,
>
>Jim Langston
>
>
>
>Richard Jackson wrote:
> >
> > A strict interpretation of multithreading means that the threads have 
> access
> > to each other's variable storage in memory.  Obviously there are 
> controls on
> > this sharing.  Your description below is for multi - processes and multi -
> > threads.  Separate processes cannot access each other's variables.  It may
> > not matter to the original requester - but then again it might.  If you use
> > separate processes and you want them to share global data, I submit that a
> > shared named user space would be a better solution.  There is a 
> "compare and
> > swap" or "test and set" function to control concurrent updating.
> >
> > Richard Jackson
> > (speaking only for myself)
> >
> > -----Original Message-----
> > From: owner-rpg400-l@midrange.com [mailto:owner-rpg400-l@midrange.com]On
> > Behalf Of Rich Duzenbury
> > Sent: Wednesday, February 28, 2001 10:42 AM
> > To: RPG400-L@midrange.com
> > Subject: Re: Multithreaded Programming
> >
> > The simplest multithread mechanism I know of is SBMJOB!  Each job can wait
> > indefinitely for it's parameters (using little system resources) by waiting
> > for a data queue message.  The parent can then signal the child to start
> > processing by sending a message to the data queue.  Once the thread is
> > complete, the child can end, or if you like go back to waiting for another
> > message.  Global data can be safely shared in a data area or a database
> > record - you just have to be sure to watch your locking.
> >
> > Regards,
> > Rich
> >
> > At 04:02 PM 2/28/01 +0000, you wrote:
> > >Hi All,
> > >
> > >I need some help on creating an application(RPG/CL) which can use
> > >multithreads while running the job.
> > >Can anyone give me some direction with examples.
> > >
> > >thanks in advance,
> > >Ray.
> > >_________________________________________________________________
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> > Regards,
> > Rich
> >
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Regards,
Rich

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