RE: Workstation Computers for FLUKA

From: Paul Colin Gloster <>
Date: Tue, 30 Nov 2010 09:51:20 +0000 (UTC)

Chris Theis sent on November 26th, 2010:

|"[..] |
| |
|However, if you take a typical scientific working environment you will |
|first of all have a very heterogeneously computing environment. In |
|addition imagine the following case - you run a simulation and get some |
|results. Sometime later you re-run an old simulation (maybe also with a |
|new version of your MC code) and you get a deviation. Now the fun part |
|starts because you will have to figure out where this deviation actually |
|comes from - could it be |
| that the physics model has changed, could it be a bug or is it maybe |
|only because you have bought a new graphics card? I can assure you that |
|tracking |
| down these things can be quite a nightmare. |
| |
|I'm certainly in favor of using modern GPUs but what I want to point out |
|is that for scientific purposes the applicability comes with a number of |
|constraints. In view of quality assurance you would first of all have to |
|ensure homogeneous computing environments until we reach the stage where |
|GPUs have become standardized enough (this should hopefully happen |
|soon!). [..] |
|[..] |
| |
|[..]" |

Hi again,

I am sorry that I forgot to respond to this part of the email

For particular circumstances it is true that changing the hardware for
real numbers would compromise an otherwise valid simulation. However,
in many cases instead if you get drastically different results then
you would not have a firm foundation to trust one type of hardware
instead of another and hence the simulations which they produce. If
you use just one type of hardware and change nothing except the
pseudorandom seed in many different runs of the same input, and the
results are all drastically different from each other, then you would
also have a reason to be sceptical. If the different pseudorandom
seeds (or the different types of hardware) produced results which were
within reasonable statistics of each other, then that would be

Paul Colin
Received on Wed Dec 01 2010 - 15:05:43 CET

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