[gmx-users] which item is gpu wait for cpu?

[Mark Abraham]

On Thu, Sep 25, 2014 at 11:57 AM, xiexiaobin at sjtu.edu.cn <
xiexiaobin at sjtu.edu.cn> wrote:

> Thanks.And I have another question want to ask.
> I used the command "mdrun_mpi -v -deffnm test" to run the .tpr file and
> find some new information in my log file:
>
>  GPU timings
>
> -----------------------------------------------------------------------------
> Computing: Count Wall t (s) ms/step %
>
> -----------------------------------------------------------------------------
> Pair list H2D 501 0.364 0.726 0.4
> X / q H2D 20001 4.153 0.208 4.5
> Nonbonded F kernel 18800 77.657 4.131 84.5
> Nonbonded F+ene k. 700 4.060 5.800 4.4
> Nonbonded F+prune k. 400 2.121 5.303 2.3
> Nonbonded F+ene+prune k. 101 0.717 7.103 0.8
> F D2H 20001 2.873 0.144 3.1
>
> -----------------------------------------------------------------------------
> Total 91.946 4.597 100.0
>
> -----------------------------------------------------------------------------
>
> Force evaluation time GPU/CPU: 4.597 ms/5.245 ms = 0.876.
>
> But I used to use the some command and didn't appear such information.Does
> anyone know why?
>

That's a breakdown of the timings that CUDA cannot always measure.


> I also find that the time consuming of Nonbonded F kernel is 77.657s but
> the time consuming of force is only 55.263s.Does the force item include
> non-bonded force?


No, it's non-PME work being done on the CPU (e.g. bonds, restraints,
free-energy short-ranged)

Mark

If it was true,why the Nonbonded F kernel takes more time than the force ?
>
>
>
> xiexiaobin at sjtu.edu.cn
>
> From: Szilárd Páll
> Date: 2014-09-24 17:45
> To: Discussion list for GROMACS users
> CC: gromacs.org_gmx-users
> Subject: Re: [gmx-users] which item is gpu wait for cpu?
> On Wed, Sep 24, 2014 at 4:57 AM, xiexiaobin at sjtu.edu.cn
> <xiexiaobin at sjtu.edu.cn> wrote:
> > I think that the items (wait GPU nonlocal) and (wait GPU local) in log
> file are the time consuming that cpu wait for gpu. And Does anyone know
> that which item is the time consuming that gpu wait for cpu in log file?
>
> Due to a CUDA runtime limitation, that can not measured except for the
> no domain-decomposition case (where it is expressed as overlap).
>
> >
> >
> > xiexiaobin at sjtu.edu.cn
> > --
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