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From: jody (jody.xha_at_[hidden])
Date: 2007-10-25 12:38:28


HI
I'm not sure if that is a problem,
but in MPI applications you shoud
use MPI_WTime() for time-measurements

Jody

On 10/25/07, 42aftab_at_[hidden] <42aftab_at_[hidden]> wrote:
> Hi all,
> I am a research assistant (RA) at NUST Pakistan in High Performance
> Scientific Computing Lab. I am working on the parallel
> implementation of the Finitie Difference Time Domain (FDTD) method
> using MPI. I am using the OpenMPI environment on a cluster of 4
> SunFire v890 cluster connected through Myrinet. I am having problem
> that when I run my code with let say 4 processes. Process 0 takes
> about 3 times more time than other three processes, executing a for
> loop which is the main cause of load imbalance in my code. I am
> writing the code that is causing the problem. The code is run by
> all the processes simultaneously and independently and I have timed
> it independent of segments of code.
>
> start = gethrtime();
> for (m = 1; m < my_x ; m++){
> for (n = 1; n < size_y-1; n++) {
> Ez(m,n) = Ez(m,n) + cezh*((Hy(m,n) - Hy(m-1,n)) -
> (Hx(m,n) - Hx(m,n-1)));
> }
> }
> stop = gethrtime();
> time = (stop-start);
>
> In my implementation I used 1-D array to realize 2-D arrays.I have used
> the following macros for accesing the array elements.
>
> #define Hx(I,J) hx[(I)*(size_y) + (J)]
> #define Hy(I,J) hy[(I)*(size_y) + (J)]
> #define Ez(I,J) ez[(I)*(size_y) + (J)]
>
> Can any one tell me what am I doing wrong here, or macros are creating the
> problems or it can be related to any OS issue. I will be looking forward
> for help because this problem has stopped my progress for the last two
> weeks
>
> regards aftab hussain
>
> RA High Performance Scientific Computing Lab
>
> NUST Institue of Information Technology
>
> National University of Sciences and Technology Pakistan
>
>
>
>
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