Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!ncrlnk!ncrcae!hubcap!wen-king
From: wen-king@csvax.caltech.edu (Wen-King Su)
Newsgroups: comp.parallel
Subject: Re:  using network machines as compute servers
Message-ID: <7345@hubcap.clemson.edu>
Date: 6 Dec 89 14:00:44 GMT
Sender: fpst@hubcap.clemson.edu
Lines: 64
Approved: parallel@hubcap.clemson.edu

>From: carriero-nicholas@YALE.EDU (Nicholas Carriero)
<In article <7300@hubcap.clemson.edu> wen-king@csvax.caltech.edu (Wen-King Su) writes:
>>>From: larsa@nada.kth.se (Lars Andersson)
<><Consider the following: One "master" puts  "tasks" in a batch, there to be
>>>picked up by the "slaves" as each completes its current task. When a slave
<><completes a task it puts the solution in an appropriate batch, there to be
>>>picked up and stored by the master (depending on the problem, one might want
<><to write directly to a file ...). 
>>
<>This can't be that difficult.  You write a batch process (listed below).
>
<[54 Lines of code to implement a batch process deleted.]
>
<You're right, it's not that difficult.  Why should the user have to
>think about (let alone design and implement) a 'batch' process she
<doesn't need?
>
<Attached is a skeletal solution in C-Linda for the master and the
>worker (i.e. the control structure for the whole problem), but this
<isn't a Linda ad (really!)---solutions with a similar structure could
>be given in any number of systems.

[a bunch of C-Linda lines deleted]

First of all, you are right; the same solution given in C-Linda can just as
easily be written in the generic C language used by Cosmic Environment.  Let
me make it clear that CE is not produced by somebody sitting around, thinking
about how one might program a multicomputer.  We do not have a person who
earns his degree by creating the Cosmic Environment.  We are all multicomputer
users and application programmers --- I am an author of CE and my project is
distributed discrete-event simulation.

Cosmic Environment is the result of people like me who wanted to protect our
investments.  All too frequently, we find ourselves wasting valuable time
supporting the same programs on several incompatible systems.  We find that
our programs got stuck with systems that becomes obsolete.  We also find
that, although many systems are full-featured and come with everything plus
a kictchen sink, they are almost always mis-focused, and we are unable to do
want we wanted without a lot of work.

We understand that the programmer knows exactly what he need, and the system
aught to give him all the tools he will need, no less but no more.  (We mean
it, and to illustrate that, the programming manual for CE is only 24 pages
long, typesetted in 11 points fonts.)  We have settled on a set of simple,
easy to understand, and easy to implement C primitives which we share with
the public in the form of the Cosmic Environment.  It makes our jobs simpler
and it protects the value of our work.  We use it daily for applications on
several multicomputers we own and for the set of SUN workstations we have.
This week, I am using a CE program that runs a batch which serves a set of
programs running on a dozen workstations.  Each program runs a copy of the
CMU COSMOS circuit simulator to evaulate the performance of one student's
circuit layout for the final grade in their VLSI design class.  Here, my
requirement is a distributed system that allows me to run a program that I
do not want to modify (or know how to modify).  A batch in CE comes handy.

Now, back to the problem at hand.  If the programmer finds it suits his need
to approach a problem using the master/worker model you described, then no
problems.  If you or I want to suggest an alternative solution, no problems
either.  But if the programmer needed a batch, I know I would want to have
simple ways to build my own d*mn batch.

/*------------------------------------------------------------------------*\
| Wen-King Su  wen-king@vlsi.caltech.edu  Caltech Corp of Cosmic Engineers |
\*------------------------------------------------------------------------*/