[Beowulf] Newbie Question

Jim Lux James.P.Lux at jpl.nasa.gov
Mon Feb 7 12:55:34 EST 2005


At 06:39 AM 2/7/2005, Mark Westwood wrote:
>Hi Monang
>
>Here's my contribution to your decision about which language you program 
>in for your cluster:
>
>Suppose that you know Java well, but not C.  Suppose that it will take you 
>6 months to learn C well enough to be able to write your programs in 
>it.  In those 6 months you can do an awful lot of computing in Java.  If 
>your project is intended to last, say, 9 months, then you might decide 
>that you will program in Java because you will get more computing done 
>that way than by learning a new language.
>
>If your project will last much longer then you might decide that learning 
>C will be of benefit, because each program will be faster in C than in 
>Java.  If you're doing some calculations then I'd suggest that you allow C 
>to be 5 times faster than Java on average for cluster-type 
>computing.  Some will tell you that it is more than 10 times as fast (and 
>it is for some types of computation), others that it is no faster (which 
>is true for some types of computation).

I would agree with Mark.  I've been faced by a similar decision.. do we do 
the calculations in Excel using Visual Basic for Applications (VBA), Visual 
Basic, or C++, or Matlab, or something else.  Various pieces of the puzzle 
exist in all of these, so the problem is do we translate (for example) the 
VB into C, or, glue it all together with scripts, or rewrite from 
scratch.  Complicating this is that the people available to work on it have 
various skill sets which don't map well to any of the approaches (how many 
people do YOU know who are equally facile in VBA, C++, and Matlab??).

In our case, the goal was to demonstrate that a particular capability can 
exist at all, versus making it really fly, so we went with the cobbled 
together scripts.  It might turn out, after all, that the speed of the 
software isn't the "rate determining" factor, but that availability of 
staff is.


James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875


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