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From: fouts@bozeman.ingr.com (Martin Fouts)
Newsgroups: comp.parallel
Subject: Re: fine->medium->coarse
Message-ID: <9254@hubcap.clemson.edu>
Date: 8 Jun 90 12:25:32 GMT
Sender: fpst@hubcap.clemson.edu
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Approved: parallel@hubcap.clemson.edu

In article <9166@hubcap.clemson.edu> george%avocet@cs.utah.edu (Lal George) writes:

   I would like clarification regarding the proper meaning of 
   the terms fined grained, medium grained and coarse grained 
   parallelism. I have seen the latter two being used 
   interchangeably. Where does one typically draw the line between
   medium and coarse grained parallelism. 

Hmm.  A good indication of the problem which arises in making this
distinction is your "fine->medium->coarse" notation.  The way I think
of granularity is as a graduated scale moving from fine on the left to
coarse on the right.  There are three problems with this.  There is no
standard calibration for the scale.  The ranges overlap.  Marketing
people have gotten their hands on the definitions.

Before marketing, the range might have looked like:

 +--  As fine grained as possible
 |    As coarse grained as possible --+
 |                                    |
 v                                    v
 |----  fine  ----|
           |---- medium ----|
                     |---- coarse ----|

Now it might look like

 +--  As fine grained as possible
 |    As coarse grained as possible --+
 |                                    |
 v                                    v
 |----  fine  --------------|           ( I claim I do fine grained)
           |---- medium ----|           ( I claim you do medium grained)
           |-------------- coarse ----| ( or, I claim coarse is good enough)

The whole thing is further complicated by measuring different kinds of
granularity with the same adjectives.  For instance, pipelined
machines are sometimes said to be fine grained because of the locality
of overlap, while simd systems are sometimes said to be fine grained
because of the huge number of parallel operations that can be
performed simultaneously.

Arg.

Another futile exercise in attempting to use English as a precise
language.

Marty

--
Martin Fouts

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If you can find an opinion in my posting, please let me know.
I don't have opinions, only misconceptions.