[gmx-users] trjconv precision lost from double to single conversion

[Johnny Lu]

nevermind the 2nd question. it does reduce to about 1/10 size.

On Fri, Dec 12, 2014 at 10:41 AM, Johnny Lu <johnny.lu128 at gmail.com> wrote:
>
> When I test the disk space that I would save by getting rid the water in
> the trajectory, I found that only make the trajectory 1/4 as large as the
> original.
> The trajectory has both position and force.
>
> Yet, the proteins only have about 1/10 the number of atoms of the whole
> system.
>
> Group     0 (         System) has 29859 elements
> Group     1 (        Protein) has  2598 elements
>
> Should the trajectory file size reduced to 1/4 instead of 1/10?
>
> The command that I used was:
> echo -e "1\n1\n" | $GMXHOME/trjconv_d -f $In_Traj -o $Out_Traj -s $In_ptr
> -pbc mol -ur compact -center -force
>
> Thanks again.
>
> On Fri, Dec 12, 2014 at 10:31 AM, Johnny Lu <johnny.lu128 at gmail.com>
> wrote:
>>
>> Hi. I'm using gromacs 4.6.7
>>
>> If the trr trajectory file is from double precision calculation, and I
>> use single precision trjconv to make a single precision trr trajectory, how
>> much precision will I lose in position and in force?
>>
>> 1, 0.1, 0.01, or 0.001 angstrom and Newton?
>>
>> Is the lost of precision acceptable?
>>
>> I noticed that single precision trr seems to take about half the hard
>> disk space of double precision trr.
>>
>> Thank you.
>>
>