Newsgroups: comp.sys.transputer
From: andyr@wizzy.com (Andy Rabagliati)
Subject: Re: transputer (t8) process activation
Organization: W.Z.I.
Date: Thu, 10 Mar 1994 17:32:40 GMT
Message-ID: <CMGM2G.6Ho@wizzy.com>

In article <1994Mar9.144239.9230@jupiter.sun.csd.unb.ca>,
Brian d'Auriol <k3mi@jupiter.sun.csd.unb.ca> wrote:

>When a process deschedules(either low or high) is that process enqueued
>at the *rear* of the process queue?.

When a process is waiting for I/O, it does not appear on any process
queue. Only runnable processes appear there.

If, when you mean deschedule, you are referring to the DESCHEDULE()
(?? spelling?) predefine, or a low priority end-of-loop deschedule, you
are correct.


> There is no defined order on the outputs of c1 c2 c3. but does the
>par necessarily complete before proc1, proc2 and proc3 execute their inputs?
                 ^^^^^^^^ -- see below

>in my own mind, i consider the following. the three parallel outputs
>occur in some order sequentially, thus they are enqueued on the queue.
>(i dont care about the order that they are enqueued in) Now, the first
>output occurs - say c1 !data1. The input in proc1 now becomes active.
>is proc1 enqueued on the rear of the queue.

Yes.

> if so, then the other outputs must necessarily complete before any of
>the procs execute.

Well, if the outputting processes (assumed more complex than your above
example - is that reasonable?) were to deschedule (at low priority only)
then the first completed input might get a crack at the CPU before all
the outputs are reached. At High priority though, all the output
statements will be reached first. That does *NOT* mean that the PAR
finishes - it does not.

Not my use of the word "reached" rather than your "complete". It is a
rendezvous point - there is a moment in time, with every input/output,
when both communicating processes are at the communication point. As a
matter of interest, the last one to reach it is always the first to
leave, if both processes are at the same priority.

Cheers,    Andy.

--
The birds have vanished into the sky,	     Andy Rabagliati  andyr@wizzy.com 
   and now the last cloud drains away.			    W.Z.I. Consulting
      We sit together, the mountain and me,			(719)635-6099
         until only the mountain remains.   -- Li Po (701-762)

