[petsc-users] Getting n largest and m smallest eigenvalues from SLEPc at the same time

[Jose E. Roman]

The options -eps_largest_real -eps_smallest_real are exclusive.
The second one, overrides the first one, because both of them call  http://slepc.upv.es/documentation/current/docs/manualpages/EPS/EPSSetWhichEigenpairs.html

You should run the example twice, or create a program that calls EPSSolve() twice.

Jose


> El 27 may 2019, a las 11:36, Afrah Najib via petsc-users <petsc-users at mcs.anl.gov> escribió:
> 
> Hi,
> 
> I have very large matrices and limited CPU hours and I want to get the first n largest and m smallest eigenvalues form these matrices using SLEPc without calculating all of them.
> 
> I tried with this command :
> 
>  mpirun -n 2 ./ex4 -file bcsstk17.bin -eps_max_it 10000 -eps_ncv 24 -eps_tol 1.0e-8  -eps_type gd  -eps_nev 6 -eps_largest_real -eps_smallest_real
> 
> but it returns the first smallest eigenvalues only.
> 
> Any idea,