"vi" & Supercomputer Performance

[Booker bense]

In article <9010130128.aa04704 at WOLF.BRL.MIL> mike at BRL.MIL (Mike Muuss) writes:
>Carl -
>
>The problem with your argument is that you implicitly assume
>that it is cheaper to transfer an entire file to another machine,
>than it is to do a little editing on the file on the Cray.
>
>In my measurements (Cray XMP48 running COS 116, Cray XMP48 running
>UNICOS 3, 4, and 5, Cray-2 running UNICOS 4 and 5), for "medium" sized
>source files, it actually used *less* Cray time to suck the file into
>a screen editor (JOVE and VI were tested), modify a "few" lines,
>and write it back out, than it was to move the file to a "front end"
>and then back to the Cray.  (obviously, no screen editor on COS,
>I just measured file xfer times, and found it more expensive of
>Cray CPU time than a UNICOS FTP or RCP).
>
>Now, I would not suggest developing new code from scratch on the Cray,
>nor would I suggest using the Cray for document processing, but
>there is no reason in the world that Cray users should not be allowed
>to modify their Cray files using the Cray!  Keep the bloody intermediate
>machines (err, "front ends") out of my way, please.
>
>Obviously, new code and document processing should be done on your
>workstation.
>	Best,
>	 -Mike Muuss
>	  U. S. Army Ballistic Research Lab



- While I would be be the last person to say that emacs and vi should
not be on a CRAY. I believe the efforts toward distributed editing to
be extremely worthwhile. The consideration here is performance of the
'overall' system. An editing process requires an entry that remains in
the process table for a significant amount of time using a significant
portion of that time in system calls. Also your test of editing 'just
a few lines' is IMHO not a very typical example of how screen editors
are used. A more reasonable scenerio is the following.

I ftp my code to the cray.

It doesn't compile ( I tested it on a vax $%#@%$)

I begin editing the offending file. 

I scroll up and down , Moving from declarations to the actual line
of the error. 

Figure out that the error is a vax non-standard type declaration. 

Edit a few lines.

quit the editor.

Recompile , it runs and crashes. 

etc....

	So while I have only made a few changes, I have been in the 
editor for many minutes. All this time the editor is patiently waiting
for keypresses, unless of course my process got swapped out. Note: in
this example I have not used any more cpu time than in the test
examples above, however I have caused the scheduler that much more
grief. While I do not pretend to know the inner workings of the UNICOS
scheduler, I know trying to edit files at around 3pm here
is an exercise in patience. 

 As several earlier posters recommended I got the 'ange-ftp' package
and I highly recommend it. The difference in response time in editing
on my workstation is tremendous. I had not realized how `slow' editing
on the YMP is. Also, with a windowing system, I now have the best of
both worlds. In one window I'm logged onto the YMP using compile
commands , in another I'm editing in the emacs running on the
workstation.
 

In summary, a screen editor should be part of any supercomputer that
supports an interactive environment, however every effort should be
made to move editing off that machine. This effort should be as
transparent to the user as possible. 


-Booker C. Bense /*benseb at grumpy.sdsc.edu*/
These are my own opinions, who else would be this foolish?
%-) No coffee
&-) 2-3 cups
8-) Ready to read news.