Subject: RE: To students who havn't linked their proposal to the homework page

From: "Chiarito, Vincent P WES" <[email-masked]>
Date: Tue, 18 Apr 2000 10:42:40 -0500

I know you realize I haven't completed HW's #3 (I did do part 1 a while
back)and 4. PLease bear with me as I complete them - I expect to have them
completed by the end of this weekend. I have had an unusual schedule of
committments here in Vicksburg during the past 4 weeks inhibiting my
progress in the course during this time. I realize that I may have to be
penalized for these severly late assignments - but I hope you will still
accept them.  I have applied for new computer accounts here at ERDC to use
our ORIGIN 2K and our IBM SP (our osprey).  So, I've been learning the in's
and out's of these machines (w/o the benefit of VPL) - I have given up
trying to run on VPL except to load results to it.  But, I've had trouble
trying to put files where I want to in VPL,  e.g., I try to upload a file to
a specific directory (say to /assign3_part1) by first going to that
directory (using VPL file manager) and then uploading the file from my PC.
Well, when I try that the file does not end up in the directory I thought I
was at - instead it goes to the uppermost level of my directories (right
under chiariv/).  What do I seem to be doing wrong?
I will miss Wednesday's class due to business travel and will back in my
office to see email on Thursday.  

It looks like Monday's and Wednesday's lectures are timely for what I plan
for my project since my project involves using FFT calculations.  I was
planning on just using an FFT algorithm that would run sequentially on any
given node - where each node would process data from a given channel
(basically a SIMD use), but I see from yesterday's lecture that there are
actually parallel versions of FFT routines (I plan to try out the FFTW
routine).  Perhaps I should compare the speedup time of my multiple data
processing tasks of using a SIMD approach (using an FFT routine that runs
totally on just one given processor) vs. using a parallel version of an FFT
routine (where even though data is "sent" to one process, the calculations
could use more than one processor).  But it seems there may be communication
conflicts that are too complicated for the latter approach (unless I choose
enough nodes to exceed the number of data channels to be processed plus the
number of nodes for each process to use for the parallel FFT routine to use)
- does this observation make sense?  Thanks.

Vince Chiarito
ERDC

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From: Saleh Elmohamed <[email-masked]>
Date: Tue, 18 Apr 2000 13:02:29 -0400 (EDT)

Vince,

Your choice of the number of nodes shouldn't really depend on the size
of your data or data channels of the problem. It is next exactly the
correct approach when it comes to the mapping of the problem
onto the available hardware. May be if you have SIMD hardware at hand with 
thousands of processors then perhaps you could think of the mapping that
way, but what you have is only a limited number of nodes of MIMD
architecture. 
The point here is that you'd need to think of a mapping of your problem
without having to worry about not having enough number of processors to
take care of your data channels. 
It is really crucial to have the right mapping of the problem into the 
architecture, otherwise, you won't see much benefit from parallelism.

-Saleh