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

[Mike Atambo]

Mike (Heroux),
I have had a look at the   code you suggested, and  it led me to  find a
problem with the mpi environment here,
i have corrected that,   thank you,  i believe  we are seeing  the correct
behaviour now.
Mike.


On Thu, Jan 29, 2015 at 5:15 PM, Mike Atambo <mikeat4999 at gmail.com> wrote:

> 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.
>
>


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