On Tue, Feb 9, 2021 at 4:31 AM Chen Gang <[email protected]> wrote:

Dear Professor,

I have a question about the bjacobi+ilu, I'm in the place

src/ksp/ksp/tutorials

and running the ex2 with

mpirun -np 40 -bind-to core ./ex2 -m 2000 -n 2000 -ksp_max_it 1000000 -ksp_rtol 1e-10 -ksp_type gmres -pc_type bjacobi -sub_pc_type ilu -sub_pc_factor_levels 10 -ksp_monitor_short

on the Intel machine with 40 cores, the petsc is complied with MKL and ICC/MPIICC with O3.

I found the numerical results are not the same from time to time, although they all right, the iterations are not exactly the same from time to time. Where have I done wrong?

Humm, iterations should rarely change. You can see floating point scale differences. Try jacobi instead of ilu and/or try not using MKL.

I'm looking forward to hear you!

Best,

Gang Chen

Sichuan Univertsity, School of Mathematics, Chengdu, China