[petsc-users] Not getting scalability.

[Stephen Wornom]

Gaurish Telang wrote:
> Hi,
>
> I have been testing PETSc's scalability on clusters for matrices of 
> sizes 2000, 10,000, uptill 60,000.
>
> All I did was try to solve Ax=b for these matrices. I found that the 
> solution time dips if I use upto 16 or 32 processors. However for a 
> larger number of processors however the solution time seems to go up 
> rather than down. IS there anyway I can make my code strongly scalable ?
As the number of processors increases, the work/processor decreases. 
Therefore the communication time (mpi) will increase and the total time 
will increase slightly.
Hope this helps,
Stephen
>
> I am measuring the total time (sec) and KSP_SOLVE time in the 
> -log_summary output. Both times show the same behaviour described 
> above.   
>
> Gaurish
>


-- 
stephen.wornom at inria.fr
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Sophia Antipolis
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Tel: 04 92 38 50 54
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