[petsc-users] [SLEPc] With the increasing of processors, result change in 1e-5 and solving time increase. krylovschur for MATSBAIJ matrix's smallest eigenvalue

[Runfeng Jin]

Hi,
 When I try to increase the number of processors to solve the same
matrix(to acquire the smallest eigenvalue) , I find all the results differ
from each other within the  1e-5 scope (Though the ||Ax-kx||/||kx|| are all
achieve 1e-8)  . And the solve time are first decreasing then increasing.
my question is
(1) Is there anyway to make the result more constant
(2)  Does the time decreasing because the matrix dimension are too small
for so many processors? Is there any way to reduce the solve time when
increasing the number of processors?

Thank you!
Runfeng


matrix type  MATSBAIJ
matrix dimension  2078802
solver krylovschur
blocksize 1
dimension of the subspace   PETSC_DEFAULT
number of eigenvalues   6
the maximum dimension allowed for the projected problem   PETSC_DEFAULT
-eps_non_hermitian

number of processors result    solve time
16 -302.06881196  526
32 -302.06881892  224
64 -302.06881989  139
128 -302.06881236  122
256 -302.06881938  285
512 -302.06881029  510
640 -302.06882377  291
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20230712/6d31dd14/attachment.html>