Article View: mod.os
Article #55Re: Classifying/defining dist. comp., parallelism, concurrency
From: darrell
Date: Fri, 13 Feb 1987 02:28
Date: Fri, 13 Feb 1987 02:28
48 lines
2856 bytes
2856 bytes
Re: terminology
Michael Scott posts:
>I find it useful to keep distinct the meanings of the words "concurrent",
>"parallel", and "distributed." In the interests of broadening the discussion,
>I suggest the following definitions:
>
> "Concurrent" implies the simultaneous existence of more than one
> thread of control.
>
> "Parallel" implies the simultaneous *execution* of more than one
> thread of control.
>
> "Distributed" implies interaction between threads of control on
> processors that share no physical memory.
>
>Parallel and distributed both imply concurrent.
>Most distributed computations are parallel.
>Coroutines are concurrent but not parallel.
The problem is much worse that this. [Pull out my classic Indian
Blindmen describing Nude elephant slide: an elephant is like a wall,
no it's like a snake, no, you're both wrong, like a tree...]
Other people refer to real-time systems as concurrent systems, also note
Concurrent Computer [formerly Perkin-Elmer], and so forth.
The Cray and other worlds have problems with: multiprogrammed (easy),
multiprocess(or/ing [surprising hard]), multitasking [also surprisingly
hard, lots of name collisions here], micro-tasking, et. al. And I set
Marty Fouts a little thing about Loosely-coupled versus tightly coupled
processing. The use of terminology is not only abomitable, but
detrimental.
Exercise left to the reader: do some research akin to parallel or
whatever computing. Stop using the words "Parallel Process" for a day.
Next day remove the obvious synonyms like "Multiprocess," one day at a
time: distributed process next, etc. Describe the same concepts. See
how much you hand wave. This is akin to the exercise which the guys
(correction: humans) studying light did to understand the duelistic
nature of light (Light was a particle on MWF, a wave on TTS). Have fun.
>From the Rock of Ages Home for Retired Hackers:
--eugene miya
NASA Ames Research Center
eugene@ames-aurora.ARPA
"You trust the `reply' command with all those different mailers out there?"
"Send mail, avoid follow-ups. If enough, I'll summarize."
{hplabs,hao,nike,ihnp4,decwrl,allegra,tektronix,menlo70}!ames!aurora!eugene
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!utgpu!water!watnot!watmath!clyde!cuae2!ihnp4!ptsfa!lll-lcc!styx!ames!ucbcad!ucbvax!sdcsvax!darrell From: darrell@sdcsvax.UUCP Newsgroups: mod.os Subject: Re: Classifying/defining dist. comp., parallelism, concurrency Message-ID: <2712@sdcsvax.UCSD.EDU> Date: Thu, 12-Feb-87 21:28:08 EST Article-I.D.: sdcsvax.2712 Posted: Thu Feb 12 21:28:08 1987 Date-Received: Sat, 14-Feb-87 12:48:13 EST Sender: darrell@sdcsvax.UCSD.EDU Organization: NASA Ames Research Center, Moffett Field, Calif. Lines: 48 Approved: mod-os@sdcsvax.uucp