[OT] Maximum performance on single processor ?

Daniel Kidger Daniel.Kidger at quadrics.com
Fri Jun 20 13:04:39 EDT 2003


-----Original Message-----
> I have an existing application which is part of a project. I have
> the source code. It is Fortran. It *can* be parallelized, but we
> would rather spend our time on the other parts of the project
> which need to be written from scratch *first*.

Fortran is not a problem - for numerical work it should be able to beat C
95% of the time IMHO

> The application is to run in real time, that is the user does something
> and as a function of user input and the calculation with the fortran
> program that I described, there is a correponding feedback to the
> user on the screen (and in some Virtual Reality equipment).

A few years ago, I was involved in a project that involved doing Finite
Elements within a VR environment.
It can be done, but you must look closely at your application code to see
*why* it is taking over 1000 milliseconds per step: 
  Do you know which bit of code takes the most time? 
  Can you save small arrays and such like to avoid recalculation?
  How are you getting new data to/from the Fortran - reading and writing
files is easy to implement but far too slow for VR.
  Are you using the appropriate matrix maths libraries for your platform (eg
mkl, atlas, libgoto, etc.)? I hope that you don't have any matrix multiplies
as 3 nested Do-loops!
  and even.. Can you use any spare CPUs in a cluster to speculatively
calculate parts of the next timestep(s) even if sometimes you have to throw
these results away?


Yours,
Daniel.

--------------------------------------------------------------
Dr. Dan Kidger, Quadrics Ltd.      daniel.kidger at quadrics.com
One Bridewell St., Bristol, BS1 2AA, UK         0117 915 5505
----------------------- www.quadrics.com --------------------
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