[gmx-users] RPM and double precision

David van der Spoel spoel at xray.bmc.uu.se
Tue Aug 21 19:08:24 CEST 2001

On Tue, 21 Aug 2001, Alan Wilter Sousa da Silva wrote:

>Hi and straightforward to the point:
>Are the RPM package compile to double precision? (I don't think so...)
>If I want double precision, I believe that I have to recompile GMX and,
>according to I've read in the manual, double precision option vanish the
>inner loops optimisations done to AMD/Pentium processors, is that right?
Yes, that is correct.

I think a lot of people want to run double precision "just to be sure it's
accurate". Indeed with double precision one does have higher level of
accuracy in energy conservation *if you don't use things like temperature
coupling, cut-off's etc*. As soon as you use either tmeperature coupling,
pressure coupling, cut-offs, it is useless to have double precision.

Someday I will do some systematic tests to prove it... 

Groeten, David.
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://zorn.bmc.uu.se/~spoel

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