[gmx-users] running in double precision

[Erik Lindahl]

Rui Qiao wrote:
> Hi, list:
> 	I wish to run one of my simulation in double precision and see
> what difference can I get. Previously I installed the single precision
> version of Gromacs and this time I just re-compile the
> "mdrun" program and leave other programs (e.g., grompp) unchanged. When I
> run the double precision code, it says:
> 
> Getting Loaded...
> Reading file init4.tpr, VERSION 3.0.5 (single precision)
> Reading file init4.tpr, VERSION 3.0.5 (single precision)
> Loaded with Money
> ....
> 
> 	Does this mean that the code is still running in single precision
> or simply tell me that the ".tpr" file is obtained from single precision
> code?

Hi Rui,

When you have a double precision binary, the header of the program will
add (double precision) to the name when you run it, e.g.:

....
                     :-)  mdrun (double precision) (-:
....


In addition, for every file you open the code will print if the file
was written in single or double precision - that's what you're seeing in
your example.

Cheers,

Erik