[petsc-users] CPU-scaling

[Torquil Macdonald Sørensen]

Hi!

You probably hit the nail on the head with the debugging suggestion. 
After reinstalling petsc using --with-debugging=0, I'm getting more 
encouraging results. For the same problem as before, but with a larger 
matrix (now 10000x10000), I'm now getting the following scaling:

# n_core    time (sec)
1                1540
2                870
3                660
4                571

which is much more promising than before. So thanks!

- Torquil

On 18/10/13 20:49, Jose E. Roman wrote:
> No, you don't need MUMPS for ex1.c with default options.
> Then I don't know what is happening. Did you build PETSc --with-debugging=0 ? You should send performance data obtained with -log_summary, otherwise we cannot guess what happens.
>
> Jose
>
>
> El 18/10/2013, a las 17:21, Torquil Macdonald Sørensen escribió:
>
>> It is a standard eigenvalue problem, and I'm only using default algorithm options, so I don't think I'm using any nontrivial spectral transformation.
>>
>> The program is just ex1.c from the documentation, available here:
>>
>> http://www.grycap.upv.es/slepc/documentation/current/src/eps/examples/tutorials/ex1.c
>>
>> FAQ #6 mentions MUMPS, which I don't have the moment, so I'll have to look into that.
>>
>> - Torquil
>>
>>
>>
>> On 18 October 2013 16:46, Jose E. Roman <jroman at dsic.upv.es> wrote:
>>
>> El 18/10/2013, a las 16:42, Torquil Macdonald Sørensen escribió:
>>
>>> Hi!
>>>
>>> I'm just starting to use SLEPc on a quad-core workstation computer (Intel Core i5-2500 CPU @ 3.30GHz).
>>>
>>> But I'm not getting the speedup that I was expecting, when increasing the number of cores. E.g. when running ex1.c from the documentation, on 1, 2, 3 and 4 cores. When asking for the 500 eigenvalues of smallest magnitude, for a 5000x5000 matrix, I'm getting the following approximate timings:
>>>
>>> # n_core  time_usage
>>> 1              480s
>>> 2              400s
>>> 3              500s
>>> 4              580s
>>>
>>> Should I not expect a speedup for n_core > 2?
>>>
>>> The example is using the krylovschur algorithm. For all four runs, the program states "Number of iterations of the method: 33".
>>>
>>> I'm using PETSc 3.4.3, SLEPc 3.4.3, OpenMPI 1.6.5, and everything is compiled using GCC 4.8.1 or 4.8.2.
>>>
>>> Best regards
>>> Torquil Sørensen
>>>
>> Is it a generalized eigenproblem and/or are you doing shift-and-invert? In that case, have a look at FAQ #6 http://www.grycap.upv.es/slepc/documentation/faq.htm
>>
>> Jose
>>
>>