[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?


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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