Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!wuarchive!emory!hubcap!ciancarini-paolo
From: ciancarini-paolo@CS.YALE.EDU (paolo ciancarini)
Newsgroups: comp.parallel
Subject: Re: parallel programming model
Message-ID: <12233@hubcap.clemson.edu>
Date: 13 Dec 90 12:49:05 GMT
Sender: fpst@hubcap.clemson.edu
Organization: Yale University Computer Science Dept., New Haven, CT 06520-2158
Lines: 33
Approved: parallel@hubcap.clemson.edu

In article <12221@hubcap.clemson.edu> hshi@maytag.waterloo.edu writes:
>A naive question:
>	We have two parallel programming models: shared memory model via
>shared variables and distributed memory model via message passing. 
>Is there any model which is some where between? Will it be more suitable
>for the persent comptuter architectures?

A naive answer:
>From a linguistic point of view, "Infinite systems exist" (Dedekind). :)

More seriously, I would say that Linda'a Generative communication
through a Tuple Space is different from both.
I believe that the Tuple Space model, that can be called also
the blackboard model because it shares many interesting features with this
architectural paradigm for AI applications,
is NEITHER a msg passing model, because agents do not know
about each other and the Tuple Space is Shared and communications are
associative, NOR a shared memory
model because agents do not shared variables or a global environment
(in fact, for Linda exist both shared memory implementations and
distributed memory implementations, but this is another issue).

>From a semantic point of view, however, it seems to me that 
we have only two models: the CCS interleaving model and the
Petri Net distributed model. It is unclear to me if does exist
a third basic model in the sense that Linda seems to be basically
different from shared memory and msg passing.
Maybe the Chemical Abstract Machine could be the basis for such
a third model. By the way, the CHAM has many features in common
with Linda.

Paolo Ciancarini
Universita' di Pisa and Yale Computer Science Dept.