[gmx-users] Compatibility of Files Between Version, Precision, and Compilation

[Johnny Lu]

Is it possible to run equilibration with mdrun of mixed precision, then run
production md with mdrun of double precision?

On Tue, Sep 16, 2014 at 8:24 PM, Johnny Lu <johnny.lu128 at gmail.com> wrote:

> Will gromacs 4.5 double precision (which has altivec support) run faster
> on the power7 cluster than 4.6.7 or 5.0.1?
> Are there any bugs that I have look out if I use gromacs 4.5 double
> precision mdrun on a cluster that only has cpu?
>
>
> On Tue, Sep 16, 2014 at 11:20 AM, Mark Abraham <mark.j.abraham at gmail.com>
> wrote:
>
>> On Tue, Sep 16, 2014 at 4:19 PM, Johnny Lu <johnny.lu128 at gmail.com>
>> wrote:
>>
>> > that machine without sse2 is a power7 cluster.
>> > It has altivec 128 simd. I wonder if gromacs can use that?
>> >
>>
>> Not right now. Maybe in future GROMACS versions.
>>
>>
>> > Where can I find the official compilation switches for power7 (xlc or
>> gcc)?
>> >
>>
>> -O3 and hope the compiler is better than any ever made.
>>
>> Mark
>>
>>
>> > On Tue, Sep 16, 2014 at 10:03 AM, Mark Abraham <
>> mark.j.abraham at gmail.com>
>> > wrote:
>> >
>> > > On Tue, Sep 16, 2014 at 3:06 PM, Johnny Lu <johnny.lu128 at gmail.com>
>> > wrote:
>> > >
>> > > > Hi.
>> > > >
>> > > > For cpt, gro, edr, and trr files, can I continue from one version
>> (4.66
>> > > or
>> > > > 5.01) and precision (single or double), with gromacs of another
>> version
>> > > > (4.6.6, or 5.0.1), precision,
>> > >
>> > >
>> > > Yes, if the relevant features are implemented in both versions. But
>> you
>> > > should never want to do that.
>> > >
>> > > > and on another machine?
>> > >
>> > > Always
>> > >
>> > > So far, it seems that tpr file compiled on a machine with sse2 and
>> > gromacs
>> > > > 4.6.6 double precision causes segmentation fault on another machine
>> > > without
>> > > > sse2 and with gromacs 4.6.6 double precision.
>> > > >
>> > >
>> > > Extremely unlikely. The .tpr file format has been no-problems portable
>> > for
>> > > about a decade ;-) But if the machine doesn't even have SSE2, then it
>> is
>> > > only good for warming your coffee.
>> > >
>> > > Mark
>> > >
>> > > Thank you (again).
>> > > > --
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>
>