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Subject: Re: [OMPI users] Regarding the execution time calculation
From: Eugene Loh (eugene.loh_at_[hidden])
Date: 2012-05-05 12:04:26


MPI_Wtime() returns the elapsed time since some arbitrary time in the
past. It is a measure of "wallclock" time, not of CPU time or anything.

On 5/4/2012 3:08 PM, Jingcha Joba wrote:
> Lets say I have a code like this
> start = MPI_Wtime()
> <Run the solver>
> stop = MPI_Wtime();
> What happens when right after start=MPI_Wtime(), the timeslice of the
> process ( from the operating system's perspective not the MPI
> process) is over, and the operating system schedules a next process,
> after saving the context switch, and eventually this application would
> resume, once its process is scheduled back by the os.
> Does MPI_Wtime() takes care of storing/updating the time when this
> happens?
> Of course, part of the answer lies in the implementation of Wtime.
>
> On Fri, May 4, 2012 at 3:53 AM, Jeff Squyres <jsquyres_at_[hidden]
> <mailto:jsquyres_at_[hidden]>> wrote:
>
> On May 3, 2012, at 2:02 PM, Jingcha Joba wrote:
>
> > Not related to this question , but just curious, is Wtime
> context switch safe ?
>
> Not sure exactly what you're asking here...?
>
> --
> Jeff Squyres
> jsquyres_at_[hidden] <mailto:jsquyres_at_[hidden]>
> For corporate legal information go to:
> http://www.cisco.com/web/about/doing_business/legal/cri/
>
>
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