[petsc-users] SLEPC no speedup in parallel

[Perceval Desforges]

Hello, 

After carefully looking at the example in the tutorial suggested in
section 3.4.5 of the manual, I managed to determine that the problem was
caused by me calling EPSSetFromOptions(eps) after
EPSKrylovSchurSetPartitions(eps,size) and not before. It now works fine.


Sorry! 

Best regards, 

Perceval, 

Le 2019-11-04 18:45, Jose E. Roman a écrit :

> Did you follow the instructions in section 3.4.5 of the SLEPc users manual?
> Send the output of -eps_view
> 
> Jose
> 
>> El 4 nov 2019, a las 18:33, Perceval Desforges via petsc-users <petsc-users at mcs.anl.gov> escribió:
>> 
>> Dear petsc and slepc developpers,
>> 
>> I am using slepc to solve an eigenvalue problem. Since I need all the eigenvalues in a certain interval, I use the spectrum slicing technique with mumps. However I do not understand: when I run my code with more than one processor, there is no speedup at all, and it even slows down, and I don't understand why.
>> 
>> I wanted to test further and I ran the same code without spectrum slicing, and asking for about the same amount of eigenvalues. The calculation was much slower (about 10 times slower), but using more than one processor sped it up.
>> 
>> Is this normal behavior or am I doing something wrong?
>> 
>> Thanks,
>> 
>> Best regards,
>> 
>> Perceval,
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20191105/46771ea7/attachment.html>