Path: utzoo!mnetor!uunet!husc6!bbn!gatech!hubcap!Ed
From: segall%clash.rutgers.edu@RELAY.CS.NET (Ed Segall)
Newsgroups: comp.hypercube
Subject: Difficulty of programming in parallel
Message-ID: <832@hubcap.UUCP>
Date: 6 Jan 88 21:29:30 GMT
Sender: fpst@hubcap.UUCP
Lines: 54
Keywords: Survey of experience
Approved: hypercube@hubcap.clemson.edu

One of the strong selling points (or claims, anyway) for many 'parallel'
computers, especially shared memory multiprocessors and vector
processors with vectorizing compilers, is that these are much easier
to program than distributed memory multiprocessors.

I have observed the degree of difficulty that experienced sequential
programmers have in dealing with a hypercube-based distributed-memory
computer.  I would like to know if that is a universal experience, and
if not, what distributed-memory systems are easier to program
(especially message-passing architectures), and what makes them
easier.

The reason for this query is that I am studying the programming
environment for such machines, and I'm trying to come up with ways to
improve it. I have a few ideas, and I'd like to see how they compare
with the experiences of others.

Any information you may have on systems, languages, hardware or
environments which makes a significant difference to the development
process would be useful.  I am especially interested in your feelings
as to what _issues_ are most relevant, though even info such as "Machine
Y in language X is awful; machine a in language B is much easier to
develop (and debug) on" is somewhat interesting.


I realize that there are a few tradeoffs here - the newest hardware is
unlikely to have the most bug-free software, for example.  So,
obviously software environments that have fewer bugs will be easier to
use.  Certainly, I am looking for information about this tradeoff, but
I'm much more interested in others.  For example, are there some
environments which are easy to use but don't produce the most
efficient programs?  I am aware that there are a few levels of OS
support for some of the Caltech cubes, giving varying degrees of speed
v. difficulty in coding.  This is closer to my goal, though I am also
interested in experience with even higher-level development support.


I will gladly summarize information I recieve to the net.  Perhaps
this will open up an interesting discussion.  (More importantly,
perhaps it will help to get some user-friendly software written.)


Thank you,


Ed Segall


Please reply by email, as this is a moderated newsgroup, and I am
interested in as many responses as possible.
-- 

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