[gmx-users] single X double precision

[Anton Feenstra]

Luciane Vieira de Mello wrote:
> Dear all,
> 
> It is maybe a naive question, but since I am reinstalling Gromacs in my
> machine, it would be nice to better understand the difference in results
> we get when using a single or double precision. Is double better but
> slower? I get the impression we hardly use double precision, by the bit "
> you never know when you might need.." in the sentence:

Double precision is indeed slower, but it is not better per se. For some
specific applications the additional precision is needed (e.g. for normal
modes analysis), but for regular EM and MD, there are other sources of
error that are much worse than the limit of the single precision.


It is good, also, to remember that usually MD simulations are run at
temperatures of 300K (or more). That means there is a lot of thermal noise
in the system already, the added 'noise' from single precision errors is
totally neglectable in comparison.


-- 
Groetjes,

Anton
  _____________ _______________________________________________________
|             |                                                       |
|  _   _  ___,| K. Anton Feenstra                                     |
| / \ / \'| | | Dept. of Pharmacochem. - Vrije Universiteit Amsterdam |
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|             | Feenstra at chem.vu.nl - www.chem.vu.nl/~feenstra/       |
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