Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!gatech!hubcap!Eugene
From: eugene@pioneer.arc.nasa.gov (Eugene N. Miya)
Newsgroups: comp.parallel
Subject: Re: parallel numerical algorithms
Message-ID: <1684@hubcap.UUCP>
Date: 23 May 88 12:42:26 GMT
Sender: fpst@hubcap.UUCP
Lines: 36
Approved: parallel@hubcap.clemson.edu

for comp.parallel:
>Although I am mostly interested in true parallelism, I wouldn't mind
>receiving algorithms based on vectorization, and such like.

The English language is marvelously vague.  I wish I knew what 'true'
parallelism is or was.  Ortega now has a new book and there are several
others (see my bibliography).

I really dislike the word "parallelism."  The problem is Whorfian and an
example hit me in March.  I was attending this meeting in Oregon and one
speaker (James Hack, a atmospheric physicist, a meterologist at NCAR) was
giving an overview of his community's computing problems [I used to work with
weather models myself, so the terrain is familiar].

We were humbled by this man's problems (O(n^3.5)) and he admitted he was not
a computer scientist [he was humbled by our problems].  Then he placed a view
graph of a 3-D plot of Amdahl's law, one axis was "percent vectorization" and
the other domain axis was "percent parallelism" done using the well known
NCAR graphics package displaying the spike at 100% vectorization and
parallelization (blah, what a word).  This graph disturbed me, there was
something wrong, and later (days unfortunately) my linear algebra background
came to the elegant conclusion that he was assuming these two things were
orthogonal.  That was his fallacy.  Now until we refine our terminology and
get an appreciation for the problems created by side-effects, shared memory,
etc., we won't solve many fundamental problems.

If we are going to make a distinction between vector and parallel, it had
better have better basis for making that distinction.

Another gross generalization from

--eugene miya, NASA Ames Research Center, eugene@aurora.arc.nasa.gov
  resident cynic at the Rock of Ages Home for Retired Hackers:
  "Mailers?! HA!", "If my mail does not reach you, please accept my apology."
  {uunet,hplabs,hao,ihnp4,decwrl,allegra,tektronix}!ames!aurora!eugene
  "Send mail, avoid follow-ups.  If enough, I'll summarize."