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From: don@ohm.york.ac.uk (Don Goodeve)
Newsgroups: comp.sys.transputer
Subject: Re: Re producers and consumers
Message-ID: <1991Feb12.153320.13923@ohm.york.ac.uk>
Date: 12 Feb 91 15:33:20 GMT
References: <1991Feb6.122949.8210@rodan.acs.syr.edu>
Organization: Electronics Department, University of York, UK
Lines: 51

in article <1991Feb6.122949.8210@rodan.acs.syr.edu>, greeny@wotan.top.cis.syr.edu (Jonathan Greenfield) says:

> Occam is the rather ugly result of one attempt at including the elegant
> concepts of CSP in a practical and efficient programming language.
> 
> Jonathan

Hmmm. well.

The issue as to the aesthetic nature of occam is a rather subjective
one. In my own experience, Occam (2) provides a consise, clear and
expressive medium for coding parallel applications. Competitors such
as parallel C etc. do not combine communications particularly elegantly
and cause programmers to err on the side of coarse-grain programming.

Occam and the transputer go together, both being developed along the lines
of Hoares' CSP together. As a result, Occam is about 30% or so more efficient
on the transputer in terms of binary size and execution speed than any other
programming medium. This may be seen as a limitation.

As a counter to this I would suggest that a general-purpose parallel machine
needs a solid foundation. The combination of the transputer and occam does
provide a unified foundation and is the only example of its' kind.

The CSP notation is perhaps not the most expressive or useful notation. In a lot
of ways it is limited in my opinion, but is very useful nevertheless. Milners'
CCS provides a greater flexibility and expressiveness although it does not
directly map to a language in the way that CSP does.

The advantage of basing a complete system design on such a model as CCS (CSP) is
the versatility that results. Any parallel programming language / paradigm can
be represented in the form of CCS. A system which can efficiently manage a
CCS-like language should therefore be able to support any paradigm built
on this foundation.

Some incomplete thoughts but I think you get the idea.

As regards shared memory, why not?? - OK so suddenly multiple processes have
to be bundled together to talk to the same section of memory (or to the same
device ...). This is NOT a problem, I agree that large shared memories are
bad news on the implementation front, but shared memory objects are not
necassarily a bad idea.

Enough rambling..... Back to work.....

 

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| Don --- Well why not? Someone has got to be!|
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