Hi Alan, I don't think using single precision is much of a problem when using thermostats, regardless of the constraint on the water.
See also Berks' comments: http://oldwww.gromacs.org/pipermail/gmx-users/2010-March/049137.html http://oldwww.gromacs.org/pipermail/gmx-users/2010-March/049152.html Ran. Alan wrote: > Hi there, > > From what I've read and known, here in the list as well, one of the > main reasons why Gromacs run in single precision is because it has > LINCS, besides SHAKE, which I believe requires double precision for > accuracy. > > I am drawing such conclusion (that can be wrong) partially based on > > Lippert, R. A., Bowers, K. J., Dror, R. O., Eastwood, M. P., > Gregersen, B. A., Klepeis, J. L., Kolossvary, I., and Shaw, D. E. A > common, avoidable source of error in molecular dynamics integrators. > Journal of Chemical Physics 126, 4 (Jan. 2007), 046101–1–046101–2 > > However, in this letter article they didn't test with LINCS. I would > love to hear some comments from Gromacs developers. > > When I started in MD, developing our own MD software, all was done in > double precision, then came Gromacs blowing up this paradigm. (I am > aware that even in Gromacs, there are routines that really requires > double precision, e.g. normal mode analysis). > > Essentially I would like to understand better this double x single > approach in MD re accuracy. > > Thanks, > > Alan > > -- > Alan Wilter S. da Silva, D.Sc. - CCPN Research Associate > Department of Biochemistry, University of Cambridge. > 80 Tennis Court Road, Cambridge CB2 1GA, UK. > >>http://www.bio.cam.ac.uk/~awd28 <http://www.bio.cam.ac.uk/%7Eawd28><<
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