[petsc-users] MPI speedup

[Matthew Knepley]

On Thu, Apr 23, 2015 at 5:47 AM, siddhesh godbole <
siddhesh4godbole at gmail.com> wrote:

> Hello,
>
> I want to know about the test which is conducted just after the PETSC is
> configured on the system to assess the possible speedup by MPI processes. I
> have saved the result file which says:
> *Number of MPI processes 10*
> *Process 0 iitm*
> *Process 1 iitm*
> *Process 2 iitm*
> *Process 3 iitm*
> *Process 4 iitm*
> *Process 5 iitm*
> *Process 6 iitm*
> *Process 7 iitm*
> *Process 8 iitm*
> *Process 9 iitm*
> *Function      Rate (MB/s) *
> *Copy:       24186.8271*
> *Scale:      23914.0401*
> *Add:        27271.7149*
> *Triad:      27787.1630*
> *------------------------------------------------*
> *np  speedup*
> *1 1.0*
> *2 1.75*
> *3 1.86*
> *4 1.84*
> *5 1.85*
> *6 1.83*
> *7 1.76*
> *8 1.79*
> *9 1.8*
> *10 1.8*
> *Estimation of possible speedup of MPI programs based on Streams
> benchmark.*
>
> 1) What parameters the speedup depends on?
>

I am not sure what you are asking here. Speedup is defined as the time T on
1 process divided
by the time T_p on p processes:

  S = T/T_p


> 2) what are the hardware requirements for higher speedup? ( i was
> expecting atleast 5 times speedup after generating 10 processes.
>

STREAMS measures the speedup of vectors operations, which are very similar
to sparse matrix operations. Both
are limited by memory bandwidth.


> 3) what could possibly be done to improve this ?
>

1) You could buy more nodes, since each node has a path to memory

2) You could change algorithms, but this has proven very difficult

   Thanks,

      Matt


> i have intel® Core™ i7-4930K CPU @ 3.40GHz × 12 with 32 GB of RAM and 1 TB
> disk space.
>
>
> Thanks
> *Siddhesh M Godbole*
>
> 5th year Dual Degree,
> Civil Eng & Applied Mech.
> IIT Madras
>



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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