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Subject: Re: [OMPI users] Regarding the execution time calculation
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2012-05-04 06:55:22

You probably need to be more fine-grained in your timing. Find out exactly what is increasing in time. This is a common symptom for codes that do not scale well -- i.e., adding more MPI processes actually causes it to slow down.

On May 3, 2012, at 7:48 AM, seshendra seshu wrote:

> Hi,
> I have written an parallel program and when i run my program on 4,8,16 nodes and calculated the execution time at master using MPI_Wtime in master node. The problem the execution time is increasing rapidly like NON parallel program-55 sec, and for parallel program 2-nodes--60sec , 4-nodes 74sec, 8-node--120 sec and for 16 nodes---for 180 sec. can i know my problem in parallel version actually the time needs to be decreased but it is increasing i dont the reason. i have calculated my time as shown below
> main(argv,argc)
> {
> double start,end;
> start= MPI_Wtime;
> // done some work
> {
> // start send from master node and receiving it
> end =MPI_Wtime;
> cout<<"execution time"<<end-start;
> }
> //in slave nodes done some work
> MPI_Finalize;
> }
> Please help me in solving this problem.
> --
> M.L.N.Seshendra
> _______________________________________________
> users mailing list
> users_at_[hidden]

Jeff Squyres
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