UNIX on Cray, COS, etc.

[William P. Reeder]

In article <12452 at brl-adm.ARPA>, mike at BRL.ARPA (Mike Muuss) writes:
> Compute performance is not operating system-specific, but instead
> compiler-specific, and Cray provides substantially the same compilers
> under both systems.
Well, operating systems have a definite affect on I/O (since programs
usually use system calls (perhaps indirectly, but at some level)) and also
on scheduling and management of the job mix.  This can have a profound 
effect on the throughput of your system.  You say that UNICOS turns out to
be faster than COS on I/O (about 10%), I'm very glad to hear that.

> The UNICOS kernel on our XMP is configured for a large load, and uses
> 176 Kwds total for it's resident image,  disk, terminal, and network buffers.
I guess Cray has done a lot of work lately, last time I heard (more than a
year ago, when we were considering running UNICOS part time on our X-MP/24)
it (UNICOS) took up more memory than COS.  I'm glad to know that it doesn't
anymore.

> Having said all that, I don't think that operating system size is enormously
> important, as long as it isn't "too big".  One thing that I'm sure we can all
> agree on is that XMPs don't have enough main memory, considering their
> speed.
I'll second that.  4 Megawords really isn't much when you start talking about
2D arrays in almost any problem.  I know you can get more memory, but it is
kind of like memory in the 8086/8088, difficult to cross the boundaries from
one chunk of 4 MW (on the Cray, not the Intel) to another.  We have a few
people who got upset when COS got bigger from 1.14 to 1.15, so they didn't
want UNICOS (back when we were told it was even bigger, no longer true).

> 	pixinterp2x -s512  < image.pix |  \
> 	rsh Cray.arpa "pixfilter -s512 -lo" |  \
> 	rsh Alliant.arpa "pixmerge -n 63/0/127 -- - background.pix |  \
> 	rsh Vax.arpa "pixrot -r -i 1024 1024 | pix-fb -h"
This is the kind of thing we want to drag (probably kicking and screaming
the whole way :-) our users into doing.  There might be a problem with
response time if everyone were using the Cray in this way (because of the
scheduling difficulties - not being able to delay some job for hours or
days (or even weeks, as seems to happen around here)), but we want to
move in that direction.

> Even watching
> 100000x100000 matrices being inverted is likely to improve your
> understanding. You might gain a new understanding of the convergence
> properties of your algorithm if you could sample every Nth iteration as
> a picture on your screen.  Think about it.
I agree, but alas, most users aren't interested in doing that sort of thing.
When I worked in our User Services division I spent the majority of my time
reading manuals to people over the phone or writing the short test programs
that they should have written.  Most of the programming (if you can call it
that :-) was done by overworked and underpaid graduate students who just
wanted to get something running.

> In closing, I'd like to summarize by observing that COS isn't a "bad"
> system, it just lacks lots of things that have come to be important.
> Good interactivity, network access, and portable software are not easy
> to do without in the fast-track business of "high-tech".
Yep.

> 	Best,
> 	 -Mike Muuss
> 	  Ballistic Research Lab
 
> And, speaking of saurians and TSO, have
> you taken careful notice of of IBM's announcement about AIX (UNIX)?  It
> looks like after many years, IBM may finally be offering their customers
> some software that is as classy as their hardware.  We are flying out a
> team next week to investigate.  (Proving that I too can ramble).
I went to a "non-disclosure" meeting about AIX (that means they don't
disclose anything to us).  I am pleased that they are working on UNIX and
they have some interesting extensions in development, but getting an IBM
to talk to an ASCII terminal is going to be somewhat of a problem.  I hope
they overcome it.  We are interested in AIX and are talking to IBM.

You can learn a lot by listenning to people ramble, if you have the patience.
That's why I read stuff on the net.

-- 
William {Wills,Card,Weekly,Virtual} Reeder	reeder at emx.utexas.edu

Scholars who study dinosaurs say there were some smart dinosaurs and lots
of stupid dinosaurs.  Those smart dinosaurs came along early, but in the
survival wars, please note, the stupid dinosaurs won.

DISCLAIMER:	I speak only for myself, and usually only to myself.