[Trilinos-Users] scaling with trilinos tpetra and anasazi solvers

[Mike Atambo]

Mike (Heroux),
Thanks i will do this,  and see what kind of information i get,  i will
post back what i find to
make it easier to for  one of you to help (or explain what i may be
missing).

Mike

On Thu, Jan 29, 2015 at 4:29 PM, Heroux, Mike <MHeroux at csbsju.edu> wrote:

>  Mike,
>
>  Just to follow up a bit more:  The reason I suggest this manual approach
> is to determine if your MPI environment can scale properly.  If your cores
> are on a single workstation, you will not get full speed up on this kind of
> solver, but I am surprised you are not seeing any.  This test would help
> diagnose the issue.
>
>  Mike
>
>   From: <Heroux>, "maherou at sandia.gov" <maherou at sandia.gov>
> Date: Thursday, January 29, 2015 at 1:03 PM
> To: Mike Atambo <mikeat4999 at gmail.com>, "
> Trilinos-Users at software.sandia.gov" <Trilinos-Users at software.sandia.gov>
> Subject: Re: [Trilinos-Users] scaling with trilinos tpetra and anasazi
> solvers
>
>   Mike,
>
>
>  It is hard to say for sure why you are seeing the results you have.  One
> thing you could do is write a simple MPI code that does a vector operation
> such as:
>
>
>  int localn = 50000000/size; // size is the number of MPI ranks
>
>
>  // define arrays x, y, w appropriately
>
> // define ntrials so that the job runs a significant amount of time.
>
>
>   for (int j=0; j< ntrials; ++j)
>
>      ​for (int i=0; i< localn; ++i) w[i] += alpha*x[i] + y[i];
>
>
>  With a tridiagonal system and the power method, your computation and
> data access should be similar to the above operation.  This should give you
> some sense of what to expect.
>
>
>  Mike
>
>
>  ------------------------------
> *From:* trilinos-users-bounces at software.sandia.gov <
> trilinos-users-bounces at software.sandia.gov> on behalf of Mike Atambo <
> mikeat4999 at gmail.com>
> *Sent:* Monday, January 26, 2015 7:29 AM
> *To:* Trilinos-Users at software.sandia.gov
> *Subject:* [EXTERNAL] [Trilinos-Users] scaling with trilinos tpetra and
> anasazi solvers
>
>    My apology,  i send an earlier email to an older thread,  this is a
> correction.
>
>  Im trying to solve a  system using  tpetra and anasazi's krylov-shur,
>  but there seems to
> be no scaling with number of processors,  i tried to run  some of the
> examples, and
> they reflect the same things i saw in my code,
>
>  attached (If list accepts attachments... hoping)  is the  lesson_03
> power  method,  changed to  create a tridiagonal sparse  matrix,
> with about   50 000 000  global indices,   the run time seems the same
>  for  2 to 16 processors,
> is there something im missing?
>
>
>
>  $ time  mpirun -np 2  ./powerm.x
> real 3m16.014s
> user 3m5.610s
> sys 0m4.452s
>
>  $ time  mpirun -np 8  ./powerm.x | grep  real
> real 3m14.229s
>  user 3m7.938s
> sys 0m4.939s
>
>
>  $ time  mpirun -np 16  ./powerm.x
> real 3m18.153s
> user 3m10.202s
> sys 0m6.108s
>
>  Mike.
>
> matambo at ictp.it
> Ext .139
>
>
>


-- 
M. O. Atambo
mikeat4999 at gmail.com
matambo at ictp.it
Ext .139
Room 209.
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