Subject: CCL:Parity checking RAM in PCs

From: [email-masked] (Dr. David N. Haney)
Date: Wed, 30 Aug 1995 11:25:44 -0700 (PDT)

On Tue, 29 Aug 1995 [email-masked] wrote:

>    The bottom line is this: if you run a calculation on one of the new PCs,
> some number of bits _might_ have been randomly flipped.  My question is
> this:  Is it legitimate to report calculations done on such a computer in a
> scientific journal?

Anyone that has run a long computation can sympathize with the concern
that the computation may need to be replicated to show that no error has
occured.  However, I am not sure that anyone that has spent long hours in the
lab to verify that their experiments are valid will sympathize.  As an
experimentalist turned computational, I find it odd that computational people
generally believe that the computer hardware, software and the users's design
are so perfect that one does not need to replicate an experiment to
verify the conclusions.  I know replicating computations can be expensive
and boring (so are laboratory experiments), but this is the scientific
method.  The only answer that I see is replication, not only for parity
errors, but software errors, user errors, Murphy's Law and cosmic rays.
Then when you report the hardware, software and error found in the
experiment, colleagues might have a clue how to try and duplicate this
work.

-- 

        **************  David N. Haney, Ph.D.    ****************
        *  Haney Associates               Phone - 619-566-1127  *
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---

From: A J Turner <[email-masked]>
Date: Wed, 30 Aug 1995 21:13:53 +0100 (BST)

Hi!

Surely it is necessary to validate computational results via experimental 
results.  It is a good idea to use computers to make new and exciting 
insights into the nature as chemical reactions etc.  However, the 
insights will always be based on theory, this theory - however ab-initio 
or otherwise pure it may be - is still theory.

My point is that chemicals are not theories - they are real (let's not 
get too deep on this issue) and so no calculation - no matter how well 
replicated can be considered chemically relevant untill validated against 
experiment.

If we consider that there is error in a calculation via bit flipping - 
this may or may not give enough error to make the calculation invalid.  
It may well be the case that small errors could creap in that do not 
deflect the result enough to make in chemically irrelevant.  It is only 
comparaion with experiment that will final come down one way or the other.

All the best

Alex

I'm not sure I beleive all that myself - but it is a point of view!

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