I think a problem occured when i used long()
adalke at mindspring.com
Fri Sep 3 03:55:19 CEST 2004
Porky Pig Jr wrote:
> Incidently, if I recall, the arguments against 'very high precision'
> was coming from scientists (e.g. those dealing with quantum mechanics
> issues) rather than from programmers. The main argument was that the
> measuring tools' precision is soo well below 53bit precision available
> as 'C double' that using anything higher than that will mistakenly
> create the impression of 'very high precision of the experiment' - but
> this is just it - *mistakenly*.
Out of curiosity, I looked for the physical constant
with the most precisely measured value. It looks
to be the electron magn. moment to Bohr magneton ratio
-1.001 159 652 1859 with error of 0.000 000 000 0038
That's 1 part in 10**13. So there are a few things
which need that sort of precision.
(53 bits is about 1 part in 10**16. 10**13 needs only
I also think GIS systems need enough precision so that
single isn't good enough for large maps. 23 bits for
a 32 bit float gives about a 4m resolution while 53
bits gives about a nm resolution.
I did molecular mechanics, not QM, but I don't recall
the QM people complaining about this issue.
dalke at dalkescientific.com
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