Re: Multithreaded Programming

I am wondering, though, with a subroutine being called by 2 different
processes, are there 2 separate copies of this program running, each
with it's own variables?  If this is the case, it won't work.

If this is not the case, and if each can actually see the static variables...

D Locked        S       Like(*IN01) Static INZ(*Off)

 *** Probably need to do something to waste time in this tight loop ***
C             DoW        Locked
C             EndDo

C             Eval       Locked = *On

   Do Stuff

C             Eval       Locked = *Off

The whole theory behind this, however, is that these subroutines just
process the calls for the shared (static) memory somehow.  Maybe somethign
like...

C             CallP      SetThreadMem("MyVar", MyValue)
C             Eval       MyVar = GetThreadMem("MyVar")

this now treating the shared thread memory as an object.

But, again, I'm not sure of the scope of Static Variables in a shared Procedure.

Regards,

Jim Langston


Rich Duzenbury wrote:
> 
> 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.
> > > >_________________________________________________________________
> > > >Get your FREE download of MSN Explorer at http://explorer.msn.com
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