no parallel speedup with slepc krylovschur

Barry Smith bsmith at
Tue Jun 30 11:03:01 CDT 2009

   Running with -log_summary will tell you WHERE the code is taking  
the time and what parts are faster and slower on two processors, this  
will help you track down the problem.
Absent this information it is impossible to know why it is not  
speeding up.


On Jun 30, 2009, at 6:48 AM, Christian May wrote:

> Dear readers,
> I want to solve the following generalized eigenvalue problem in  
> parallel:
> (gnu zipped tar of the binaryoutput you get using -eps_view_binary)
> I know the approximate value of the lowest eigenvalues I'm  
> interested in, so I'm using shift-and-invert with the following  
> options:
> -eps_type krylovschur -st_type sinvert -st_shift -0.228 -eps_ncv 32 - 
> eps_nev 16 -eps_tol 1e-10
> However, when I use multiple CPUs, I cannot see any speedup. I am  
> not sure whether this is a problem of the matrix or of my system.  
> Can anybody please have a look?
> Thanks
> Christian

More information about the petsc-users mailing list